A

• advection
  Advection
  Advection, in chemistry, engineering and earth sciences, is a transport mechanism of a substance, or a conserved property, by a fluid, due to the fluid's bulk motion in a particular direction. An example of advection is the transport of pollutants or silt in a river. The motion of the water carries...
  
  
• aeroacoustics
  Aeroacoustics
  Aeroacoustics is a branch of acoustics that studies noise generation via either turbulent fluid motion or aerodynamic forces interacting with surfaces. Noise generation can also be associated with periodically varying flows...
  
  
• aerobiology
  Aerobiology
  Aerobiology is a branch of biology that studies organic particles, such as bacteria, fungal spores, very small insects, pollen grains and viruses, which are passively transported by the air...
  
  
• aerography (meteorology)
  Aerography (meteorology)
  Aerography is the production of weather charts. The information is supplied by radiosonde observations, principally. Constant-pressure charts are routinely constructed at standard air pressures. Standard air pressures are 850, 700, 500, 400, 300, 250, and 200 millibars...
  
  
• aerology
• air parcel
  Air parcel
  In fluid dynamics, within the framework of continuum mechanics, a fluid parcel is a very small amount of fluid, identifiable throughout its dynamic history while moving with the fluid flow. As it moves, the mass of a fluid parcel remains constant, while—in a compressible flow—its volume may...
  
   (in meteorology)
• Air Quality Index
  Air Quality Index
  Air quality is defined as a measure of the condition of air relative to the requirements of one or more biotic species or to any human need or purpose. Air quality indices are numbers used by government agencies to characterize the quality of the air at a given location...
  
   (AQI)
• airshed
  Airshed
  An airshed is a part of the atmosphere that behaves in a coherent way with respect to the dispersion of emissions. It typically forms an analytical or management unit.Also: A geographic boundary for air quality standards.-External links:*...
  
   (in meteorology)
• American Meteorological Society
  American Meteorological Society
  The American Meteorological Society promotes the development and dissemination of information and education on the atmospheric and related oceanic and hydrologic sciences and the advancement of their professional applications. Founded in 1919, the American Meteorological Society has a membership...
  
   (AMS)
• anabatic wind
  Anabatic wind
  An anabatic wind, from the Greek anabatos, verbal of anabainein meaning moving upward, is a wind which blows up a steep slope or mountain side, driven by heating of the slope through insolation. It is also known as an upslope flow. These winds typically occur during the daytime in calm sunny weather...
  
  
• anemometer
  Anemometer
  An anemometer is a device for measuring wind speed, and is a common weather station instrument. The term is derived from the Greek word anemos, meaning wind, and is used to describe any airspeed measurement instrument used in meteorology or aerodynamics...
  
  
• annular hurricane
  Annular hurricane
  An annular hurricane, also known as a truck tire or doughnut hurricane, is a tropical cyclone in the Atlantic or Eastern Pacific Oceans that features a large, symmetric eye surrounded by a thick ring of intense convection. This type of storm is not prone to the fluctuations in intensity associated...
  
  
• anticyclone
  Anticyclone
  An anticyclone is a weather phenomenon defined by the United States' National Weather Service's glossary as "[a] large-scale circulation of winds around a central region of high atmospheric pressure, clockwise in the Northern Hemisphere, counterclockwise in the Southern Hemisphere"...
  
   (in meteorology)
• apparent wind
  Apparent wind
  Apparent wind is the wind experienced by a moving object.-Definition of apparent wind:The Apparent wind is the wind experienced by an observer in motion and is the relative velocity of the wind in relation to the observer....
  
  
• Atlantic hurricane season
  Atlantic hurricane season
  The Atlantic hurricane season is the period in a year when hurricanes usually form in the Atlantic Ocean. Tropical cyclones in the North Atlantic are called hurricanes, tropical storms, or tropical depressions. In addition, there have been several storms over the years that have not been fully...
  
  
• atmometer
  Atmometer
  The atmometer or evaporimeter is a scientific instrument used for measuring the rate of evaporation from a wet surface to the atmosphere. It was invented by either the Dutch scientist Pieter van Musschenbroek or the Scottish mathematician and engineer Sir John Leslie .A simple set up may be made...
  
  
• atmosphere
  Atmosphere
  An atmosphere is a layer of gases that may surround a material body of sufficient mass, and that is held in place by the gravity of the body. An atmosphere may be retained for a longer duration, if the gravity is high and the atmosphere's temperature is low...
  
  
• Atmospheric Model Intercomparison Project
  Atmospheric Model Intercomparison Project
  Atmospheric Model Intercomparison Project is a standard experimental protocol for global atmospheric general circulation models . It provides a community-based infrastructure in support of climate model diagnosis, validation, intercomparison, documentation and data access...
  
   (AMIP)
• Atmospheric Radiation Measurement
  Atmospheric Radiation Measurement
  The United States Department of Energy's Atmospheric Radiation Measurement Program was created in 1989 to develop several highly instrumented ground stations to study cloud formation processes and their influence on radiative transfer...
  
   (ARM)
• (atmospheric boundary layer [ABL]) planetary boundary layer
  Planetary boundary layer
  The planetary boundary layer , also known as the atmospheric boundary layer , is the lowest part of the atmosphere and its behavior is directly influenced by its contact with a planetary surface. On Earth it usually responds to changes in surface forcing in an hour or less...
  
   (PBL)
• atmospheric chemistry
  Atmospheric chemistry
  Atmospheric chemistry is a branch of atmospheric science in which the chemistry of the Earth's atmosphere and that of other planets is studied. It is a multidisciplinary field of research and draws on environmental chemistry, physics, meteorology, computer modeling, oceanography, geology and...
  
  
• atmospheric circulation
  Atmospheric circulation
  Atmospheric circulation is the large-scale movement of air, and the means by which thermal energy is distributed on the surface of the Earth....
  
  
• atmospheric dispersion modeling
  Atmospheric dispersion modeling
  Atmospheric dispersion modeling is the mathematical simulation of how air pollutants disperse in the ambient atmosphere. It is performed with computer programs that solve the mathematical equations and algorithms which simulate the pollutant dispersion...
  
  
• atmospheric electricity
  Atmospheric electricity
  Atmospheric electricity is the regular diurnal variations of the Earth's atmospheric electromagnetic network . The Earth's surface, the ionosphere, and the atmosphere is known as the global atmospheric electrical circuit...
  
  
• atmospheric icing
  Atmospheric icing
  Atmospheric icing occurs when water droplets in the atmosphere freeze on objects they contact. This can be extremely dangerous to aircraft, as the built-up ice changes the aerodynamics of the flight surfaces, which can increase the risk of a subsequent stalling of the airfoil...
  
  
• atmospheric physics
  Atmospheric physics
  Atmospheric physics is the application of physics to the study of the atmosphere. Atmospheric physicists attempt to model Earth's atmosphere and the atmospheres of the other planets using fluid flow equations, chemical models, radiation balancing, and energy transfer processes in the atmosphere...
  
  
• atmospheric sciences
  Atmospheric sciences
  Atmospheric sciences is an umbrella term for the study of the atmosphere, its processes, the effects other systems have on the atmosphere, and the effects of the atmosphere on these other systems. Meteorology includes atmospheric chemistry and atmospheric physics with a major focus on weather...
  
  
• atmospheric stratification
• atmospheric window
  Atmospheric window
  The infrared atmospheric window is the overall dynamic property of the earth's atmosphere, taken as a whole at each place and occasion of interest, that lets some infrared radiation from the cloud tops and land-sea surface pass directly to space without intermediate absorption and re-emission, and...
  
   (see under Threats)

B

• ball lightning
  Ball lightning
  Ball lightning is an unexplained atmospheric electrical phenomenon. The term refers to reports of luminous, usually spherical objects which vary from pea-sized to several metres in diameter. It is usually associated with thunderstorms, but lasts considerably longer than the split-second flash of a...
  
  
• balloon (aircraft)
  Balloon (aircraft)
  A balloon is a type of aircraft that remains aloft due to its buoyancy. A balloon travels by moving with the wind. It is distinct from an airship, which is a buoyant aircraft that can be propelled through the air in a controlled manner....
  
  
• barometer
  Barometer
  A barometer is a scientific instrument used in meteorology to measure atmospheric pressure. Pressure tendency can forecast short term changes in the weather...
  
   ("to measure atmospheric pressure")
• berg wind
• blizzard
  Blizzard
  A blizzard is a severe snowstorm characterized by strong winds. By definition, the difference between blizzard and a snowstorm is the strength of the wind. To be a blizzard, a snow storm must have winds in excess of with blowing or drifting snow which reduces visibility to 400 meters or ¼ mile or...
  
  
• bomb (meteorology)
  Bomb (meteorology)
  Bomb is a meteorological term for a baroclinic low pressure area characterized by a rapid pressure fall of at least 24 millibars in 24 hours. It is applied only to cold-air storms...
  
  
• Bureau of Meteorology
  Bureau of Meteorology
  The Bureau of Meteorology is an Executive Agency of the Australian Government responsible for providing weather services to Australia and surrounding areas. It was established in 1906 under the Meteorology Act, and brought together the state meteorological services that existed before then...
  
   (in Australia)

C

• Canada Weather Extremes
  Canada Weather Extremes
  This table shows record weather extremes in Canada.*A snowfall season runs from July 1-June 30**Data range is from 1996 to 2009 only-See also:*List of extreme temperatures in Canada*List of weather records-External links:*...
  
  
• Canadian Hurricane Centre
  Canadian Hurricane Centre
  The Canadian Hurricane Centre is a division of the Meteorological Service of Canada, an agency of Canada's Department of the Environment, which exists to advise Canadians on the threat of tropical cyclones such as hurricanes and tropical storms...
  
   (CHC)
• Cape Verde-type hurricane
  Cape Verde-type hurricane
  A Cape Verde-type hurricane is an Atlantic hurricane that develops near the Cape Verde islands, off the west coast of Africa. The average hurricane season has about two Cape Verde-type hurricanes, which are usually the largest and most intense storms of the season because they often have plenty of...
  
  
• capping inversion
  Capping inversion
  A capping inversion is an elevated inversion layer that caps a convective boundary layer.The boundary layer is the part of the atmosphere which is closest to the ground. Normally, the sun heats the ground, which in turn heats the air just above it. Thermals form when this warm air rises into the...
  
   (in meteorology) (see "severe thunderstorms" in paragraph 5)
• carbon cycle
  Carbon cycle
  The carbon cycle is the biogeochemical cycle by which carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and atmosphere of the Earth...
  
  
• carbon fixation
  Carbon fixation
  In biology, carbon fixation is the reduction of carbon dioxide to organic compounds by living organisms. The obvious example is photosynthesis. Carbon fixation requires both a source of energy such as sunlight, and an electron donor such as water. All life depends on fixed carbon. Organisms that...
  
  
• carbon flux
• carbon monoxide
  Carbon monoxide
  Carbon monoxide , also called carbonous oxide, is a colorless, odorless, and tasteless gas that is slightly lighter than air. It is highly toxic to humans and animals in higher quantities, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal...
  
   (see under Carbon monoxide in the atmosphere)
• ceiling balloon
  Ceiling balloon
  A ceiling balloon is used by meteorologists to determine the height of the base of clouds above ground level during daylight hours.The principle behind the ceiling balloon is a balloon with a known ascent rate and determining how long the balloon rises until it disappears into the cloud.Ascent...
  
   ("to determine the height of the base of clouds above ground level")
• ceilometer
  Ceilometer
  A ceilometer is a device that uses a laser or other light source to determine the height of a cloud base. Ceilometers can also be used to measure the aerosol concentration within the atmosphere.-Optical Drum Ceilometer:...
  
   ("to determine the height of a cloud base")
• celestial coordinate system
  Celestial coordinate system
  In astronomy, a celestial coordinate system is a coordinate system for mapping positions on the celestial sphere.There are different celestial coordinate systems each using a system of spherical coordinates projected on the celestial sphere, in analogy to the geographic coordinate system used on...
  
  
• celestial equator
  Celestial equator
  The celestial equator is a great circle on the imaginary celestial sphere, in the same plane as the Earth's equator. In other words, it is a projection of the terrestrial equator out into space...
  
  
• celestial horizon
  Celestial horizon
  The celestial horizon, also called the rational horizon, is a great circle parallel to the horizon, in which a plane at right angles to Zenith and Nadir lines are passing through the centre of the earth and intersects the celestial sphere, the center of which is the center of the Earth....
  
   (rational horizon)
• celestial navigation
  Celestial navigation
  Celestial navigation, also known as astronavigation, is a position fixing technique that has evolved over several thousand years to help sailors cross oceans without having to rely on estimated calculations, or dead reckoning, to know their position...
  
   (astronavigation)
• celestial pole
  Celestial pole
  The north and south celestial poles are the two imaginary points in the sky where the Earth's axis of rotation, indefinitely extended, intersects the imaginary rotating sphere of stars called the celestial sphere...
  
  
• Celsius
• Center for Analysis and Prediction of Storms
  Center for Analysis and Prediction of Storms
  The Center for Analysis and Prediction of Storms was established at the University of Oklahoma in 1989 as one of the first eleven National Science Foundation Science and Technology Centers...
  
   (CAPS) (in Oklahoma in the US)
• Center for the Study of Carbon Dioxide and Global Change
  Center for the Study of Carbon Dioxide and Global Change
  The Center for the Study of Carbon Dioxide and Global Change is a 501 non-profit organization based in Arizona in the United States...
  
   (based in Arizona in the US)
• (Central America Hurricane of 1857: see) SS Central America
  SS Central America
  SS Central America, sometimes called the Ship of Gold, was a 280-foot sidewheel steamer that operated between Central America and the eastern coast of the United States during the 1850s. She was originally named the SS George Law, after Mr. George Law of New York...
  
   (Ship of Gold)
• Central Florida Tornado of February 2007
• Certified Consulting Meteorologist
  Certified Consulting Meteorologist
  Certified Consulting Meteorologist is the title of a person designated by the American Meteorological Society and to possess the attributes of Knowledge, Experience, and Character as they pertain to the field of meteorology...
  
  
• chaos theory
  Chaos theory
  Chaos theory is a field of study in mathematics, with applications in several disciplines including physics, economics, biology, and philosophy. Chaos theory studies the behavior of dynamical systems that are highly sensitive to initial conditions, an effect which is popularly referred to as the...
  
   (see "butterfly effect" under Chaotic dynamics)
• (Chapman cycle: see) ozone-oxygen cycle
  Ozone-oxygen cycle
  The ozone-oxygen cycle is the process by which ozone is continually regenerated in Earth's stratosphere, all the while converting ultraviolet radiation into heat. In 1930 Sydney Chapman resolved the chemistry involved. The process is commonly called the Chapman cycle by atmospheric scientists.Most...
  
  
• chemtrail theory
  Chemtrail theory
  The chemtrail conspiracy theory holds that some trails left by aircraft are actually chemical or biological agents deliberately sprayed at high altitudes for purposes undisclosed to the general public in clandestine programsdirected by government officials...
  
  
• Chicago Climate Exchange
  Chicago Climate Exchange
  The now defunct Chicago Climate Exchange was North America’s only voluntary, legally binding greenhouse gas reduction and trading system for emission sources and offset projects in North America and Brazil....
  
   (CCX)
• chinook wind
  Chinook wind
  Chinook winds , often called chinooks, commonly refers to foehn winds in the interior West of North America, where the Canadian Prairies and Great Plains meet various mountain ranges, although the original usage is in reference to wet, warm coastal winds in the Pacific Northwest.Chinook is claimed...
  
   (see "inversion smog" under Chinooks and health)
• clear-air turbulence
  Clear-Air Turbulence
  Clear air turbulence is the turbulent movement of air masses in the absence of any visual cues such as clouds, and is caused when bodies of air moving at widely different speeds meet....
  
   (CAT)
• climate
  Climate
  Climate encompasses the statistics of temperature, humidity, atmospheric pressure, wind, rainfall, atmospheric particle count and other meteorological elemental measurements in a given region over long periods...
  
  
• climate change
  Climate change
  Climate change is a significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions or the distribution of events around that average...
  
  
• Climate Diagnostics Center
  Climate Diagnostics Center
  The Climate Diagnostics Center was a project of the Cooperative Institute for Research in Environmental Sciences , itself a joint project of the National Oceanic and Atmospheric Administration and the University of Colorado at Boulder. In October 2005, it was merged with five other NOAA labs to...
  
   (in the US)
• climate engineering
• (climate forcing: see) radiative forcing
  Radiative forcing
  In climate science, radiative forcing is generally defined as the change in net irradiance between different layers of the atmosphere. Typically, radiative forcing is quantified at the tropopause in units of watts per square meter. A positive forcing tends to warm the system, while a negative...
  
  
• Climate Group
  Climate Group
  The Climate Group is a non-profit organization that works with business and government to promote clean energy to reduce global greenhouse gas emissions. The Climate Group was created in 2004 and now has offices in the UK , the US, Europe, Australia, India, mainland China and Hong Kong...
  
  
• climate house
  Climate house
  The "ClimateHouse" energy efficiency certification promotes the adoption of building construction methods that meet energy saving and environment protection criteria. The category of energy saving, determines if a building is classified as a ClimateHouse. The ClimateHouse categories provide an...
  
  
• climate model
  Climate model
  Climate models use quantitative methods to simulate the interactions of the atmosphere, oceans, land surface, and ice. They are used for a variety of purposes from study of the dynamics of the climate system to projections of future climate...
  
  
• climate modeller
• Climate Monitoring and Diagnostics Laboratory
  Climate Monitoring and Diagnostics Laboratory
  The Climate Monitoring and Diagnostics Laboratory was a climate laboratory in the National Oceanic and Atmospheric Administration /Office of Oceanic and Atmospheric Research...
  
   (CMDL) (in the US)
• Climate Outreach and Information Network
  Climate Outreach and Information Network
  The Climate Outreach and Information Network is a British charity that works with the general public to provide information about climate change and how to deal with it. Based in Oxford, it was registered as a charity in March 2008, and since then has run a number of projects and talks on climate...
  
   (COIN) (British charity)
• (climate parameters, forcings and feedbacks: see) parametrization (climate)
  Parametrization (climate)
  Parameterization in a weather or climate model within numerical weather prediction refers to the method of replacing processes that are too small-scale or complex to be physically represented in the model by a simplified process. This can be contrasted with other processes—e.g., large-scale flow of...
  
  
• (climate science: see) climatology
  Climatology
  Climatology is the study of climate, scientifically defined as weather conditions averaged over a period of time, and is a branch of the atmospheric sciences...
  
  
• climate sensitivity
  Climate sensitivity
  Climate sensitivity is a measure of how responsive the temperature of the climate system is to a change in the radiative forcing. It is usually expressed as the temperature change associated with a doubling of the concentration of carbon dioxide in Earth's atmosphere.The equilibrium climate...
  
  
• (climate simulation: see) climate model
  Climate model
  Climate models use quantitative methods to simulate the interactions of the atmosphere, oceans, land surface, and ice. They are used for a variety of purposes from study of the dynamics of the climate system to projections of future climate...
  
  
• climate surprise
• (climate techno-fix: see) climate engineering
• (climate theory: see) Charles de Secondat, Baron de Montesquieu
  Charles de Secondat, baron de Montesquieu
  Charles-Louis de Secondat, baron de La Brède et de Montesquieu , generally referred to as simply Montesquieu, was a French social commentator and political thinker who lived during the Enlightenment...
  
   (see "climate theory" in paragraph 3 under Political views)
• (climate variability: see) climate change
  Climate change
  Climate change is a significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions or the distribution of events around that average...
  
  
• (climate warming: see) global warming
  Global warming
  Global warming refers to the rising average temperature of Earth's atmosphere and oceans and its projected continuation. In the last 100 years, Earth's average surface temperature increased by about with about two thirds of the increase occurring over just the last three decades...
  
  
• (climate weapon: see) Weather Modification Operations and Research Board
  Weather Modification Operations and Research Board
  The Weather Modification Operations and Research Board was a proposed agency of the United States government, intended to promote research into weather control. A bill creating of the board was introduced in the U.S. Senate on two occasions by Texas Senator Kay Bailey Hutchinson, the first on March...
  
   (in the US) (see under Weather Control)
• climateprediction.net
  Climateprediction.net
  Climateprediction.net, or CPDN, is a distributed computing project to investigate and reduce uncertainties in climate modelling. It aims to do this by running hundreds of thousands of different models using the donated idle time of ordinary personal computers, thereby leading to a better...
  
   (CPDN) (distributed computing project)
• climatic determinism (equatorial paradox) (see also environmental determinism
  Environmental determinism
  Environmental determinism, also known as climatic determinism or geographical determinism, is the view that the physical environment, rather than social conditions, determines culture...
  
  )
• Climatic Regions of India
  Climatic Regions of India
  India has a large variation in climate from region to region, due to its vast size. India experiences climate from four major climate groups. These can be further subdivided into seven climatic types.-Tropical rainy climatic group:...
  
  
• Climatic Research Unit
  Climatic Research Unit
  The Climatic Research Unit is a component of the University of East Anglia and is one of the leading institutions concerned with the study of natural and anthropogenic climate change....
  
   (at the University of East Anglia in the UK)
• (climatic zone: see) clime
  Clime
  The seven climes was a notion of dividing the Earth into zones in Classical Antiquity....
  
  
• climatology
  Climatology
  Climatology is the study of climate, scientifically defined as weather conditions averaged over a period of time, and is a branch of the atmospheric sciences...
  
  
• clime
  Clime
  The seven climes was a notion of dividing the Earth into zones in Classical Antiquity....
  
   (climatic zone)
• Clinton Foundation
  Clinton Foundation
  The William J. Clinton Foundation is a foundation established by former President of the United States Bill Clinton with the stated mission to "strengthen the capacity of people throughout the world to meet the challenges of global interdependence." The Foundation focuses on four critical areas:...
  
   (see "Energy and Climate Change" under Goals)
• cloud
  Cloud
  A cloud is a visible mass of liquid droplets or frozen crystals made of water and/or various chemicals suspended in the atmosphere above the surface of a planetary body. They are also known as aerosols. Clouds in Earth's atmosphere are studied in the cloud physics branch of meteorology...
  
  
• cloud albedo
  Cloud albedo
  Cloud albedo is a measure of the albedo of a cloud - higher values mean that the cloud reflects more solar radiation, or more radiation is transmitted....
  
   ("a measure of the reflectivity of a cloud")
• cloud base
  Cloud base
  This article refers to meteorology. For the airborne base of the TV series Captain Scarlet and the Mysterons, see Cloudbase.The cloud base is the lowest altitude of the visible portion of the cloud...
  
   ("the lowest altitude of the visible portion of a cloud")
• cloud chamber
  Cloud chamber
  The cloud chamber, also known as the Wilson chamber, is a particle detector used for detecting ionizing radiation. In its most basic form, a cloud chamber is a sealed environment containing a supersaturated vapor of water or alcohol. When a charged particle interacts with the mixture, it ionizes it...
  
   (Wilson chamber) ("for detecting ... ionizing radiation")
• cloud condensation nuclei
  Cloud condensation nuclei
  Cloud condensation nuclei or CCNs are small particles typically 0.2 µm, or 1/100 th the size of a cloud droplet ) about which cloud droplets coalesce. Water requires a non-gaseous surface to make the transition from a vapour to a liquid. In the atmosphere, this surface presents itself as tiny...
  
   (CCNs) (see under Phytoplankton role)
• cloud cover
  Cloud cover
  Cloud cover refers to the fraction of the sky obscured by clouds when observed from a particular location...
  
  
• cloud feedback
  Cloud feedback
  Cloud feedback is the coupling between cloudiness and surface air temperature in which a change in radiative forcing perturbs the surface air temperature, leading to a change in clouds, which could then amplify or diminish the initial temperature perturbation....
  
  
• cloud forcing
  Cloud forcing
  Cloud forcing is, in meteorology, the difference between the radiation budget components for average cloud conditions and cloud-free conditions...
  
   (see "greenhouse effect" in paragraph 2)
• cloud forest
  Cloud forest
  A cloud forest, also called a fog forest, is a generally tropical or subtropical evergreen montane moist forest characterized by a persistent, frequent or seasonal low-level cloud cover, usually at the canopy level. Cloud forests often exhibit an abundance of mosses covering the ground and...
  
  
• (cloud formation: see) nephology
  Nephology
  Nephology is the study of clouds and cloud formation. British meteorologist Luke Howard was a major researcher within this field, establishing a cloud classification system....
  
  
• cloud physics
  Cloud physics
  Cloud physics is the study of the physical processes that lead to the formation, growth and precipitation of clouds. Cloud formations are composed of microscopic droplets of liquid water , tiny crystals of ice , or both...
  
  
• cloud seeding
  Cloud seeding
  Cloud seeding, a form of intentional weather modification, is the attempt to change the amount or type of precipitation that falls from clouds, by dispersing substances into the air that serve as cloud condensation or ice nuclei, which alter the microphysical processes within the cloud...
  
  
• cloud street
• cloud suck
  Cloud suck
  Cloud suck is a phenomenon commonly known in paragliding and hang gliding where pilots experience significant lift due to a thermal under the base of cumulus clouds, especially towering cumulus and cumulonimbus...
  
  
• cloudburst
  Cloudburst
  A cloudburst is an extreme amount of precipitation, sometimes with hail and thunder, which normally lasts no longer than a few minutes but is capable of creating flood conditions.-Etymology:There are similar names for such events in other languages...
  
   (see "destruction" in paragraph 2 and see "Mumbai" in paragraph 3)
• CloudSat
  CloudSat
  CloudSat is a NASA Earth observation satellite, which was launched on a Delta II rocket on 28 April 2006. It uses radar to measure the altitude and properties of clouds, adding to information on the relationship between clouds and climate in order to help resolve questions about global warming...
  
   ("a NASA environmental satellite")
• coefficient of haze
  Coefficient of haze
  The coefficient of haze is a measurement of visibility interference in the atmosphere....
  
   (in meteorology)
• cold-core low
  Cold-core low
  A cold-core low, also known as a cold low or cold-core cyclone, is a cyclone aloft which has an associated cold pool of air residing at high altitude within the Earth's troposphere. It is a low pressure system which strengthens with height in accordance with the thermal wind relationship. These...
  
  
• cold weather boot
• cold weather rule
  Cold weather rule
  A cold weather rule or cold weather law is a law or regulation that prohibits public utility companies from disconnecting customers who are unable to pay for the energy used to heat their homes during the winter. Such regulations may also require utility companies to reconnect customers during...
  
   (cold weather law) (for public utility companies)
• (coldest place on earth: see) climate of Antarctica
  Climate of Antarctica
  The climate of Antarctica is the coldest on the whole of Earth. Antarctica has the lowest naturally occurring temperature ever recorded on the ground on Earth: −89.2 °C at Vostok Station. It is also extremely dry , averaging 166 mm of precipitation per year...
  
   (see under Temperature)
• coldest temperature achieved on Earth
  Coldest temperature achieved on Earth
  The lowest temperature ever recorded at the surface of the Earth was at the Russian Vostok Station in Antarctica July 21, 1983. Lower temperatures have been achieved in the laboratory, including a record low temperature of 100 pK, or 1.0 × 10-10 K in 1999.- Early cooling :In...
  
  
• Community Climate System Model
  Community Climate System Model
  The Community Climate System Model is a coupled Global Climate Model developed by the University Corporation for Atmospheric Research with funding from the National Science Foundation, Department of Energy, and NASA...
  
  
• continental climate
  Continental climate
  Continental climate is a climate characterized by important annual variation in temperature due to the lack of significant bodies of water nearby...
  
  
• contrail
  Contrail
  Contrails or vapour trails are artificial clouds that are the visible trails of condensed water vapour made by the exhaust of aircraft engines...
  
  
• controlled airspace
  Controlled airspace
  Controlled airspace is an aviation term used to describe airspace in which ATChas the authority to control air traffic, the level of which varies with the different classes of airspace. Controlled airspace is established mainly for three different reasons:...
  
  
• controlled atmosphere
  Controlled atmosphere
  A controlled atmosphere is an agricultural storage method. An atmosphere in which oxygen, carbon dioxide and nitrogen concentrations as well as temperature and humidity are regulated.Two major classes of commodity can be stored in controlled atmosphere:...
  
   (for agricultural storage)
• convection
  Convection
  Convection is the movement of molecules within fluids and rheids. It cannot take place in solids, since neither bulk current flows nor significant diffusion can take place in solids....
  
   (see under Atmospheric convection)
• convective available potential energy
  Convective available potential energy
  In meteorology, convective available potential energy , sometimes, simply, available potential energy , is the amount of energy a parcel of air would have if lifted a certain distance vertically through the atmosphere...
  
   (CAPE) (in meteorology)
• Cooperative Institute for Atmospheric Sciences and Terrestrial Applications
  Cooperative Institute for Atmospheric Sciences and Terrestrial Applications
  The Cooperative Institute for Atmospheric Sciences and Terrestrial Applications formalizes a major collaborative relationship between the National Oceanic and Atmospheric Administration Office of Oceanic and Atmospheric Research and the Desert Research Institute...
  
   (CIASTA)
• Cooperative Institute for Arctic Research
  Cooperative Institute for Arctic Research
  The Cooperative Institute for Arctic Research is designed to be a focal point for interactions between the National Oceanic and Atmospheric Administration /Office of Oceanic and Atmospheric Research and the Arctic research community through the University of Alaska for research related to the...
  
  
• Cooperative Institute for Climate and Ocean Research
  Cooperative Institute for Climate and Ocean Research
  The Cooperative Institute for Climate and Ocean Research formalizes a major collaborative relationship between the National Oceanic and Atmospheric Administration Office of Oceanic and Atmospheric Research and the Woods Hole Oceanographic Institution .CICOR provides a framework at WHOI for...
  
   (CICOR)
• Cooperative Institute for Climate Applications and Research
  Cooperative Institute for Climate Applications and Research
  The Cooperative Institute for Climate Applications and Research formalizes a major collaborative relationship between the National Oceanic and Atmospheric Administration Office of Oceanic and Atmospheric Research and Columbia University....
  
   (CICAR)
• Cooperative Institute for Climate Science
  Cooperative Institute for Climate Science
  The Cooperative Institute for Climate Science fosters research collaborations between the National Oceanic and Atmospheric Administration /Office of Oceanic and Atmospheric Research Geophysical Fluid Dynamics Laboratory and the Princeton University.The CICS research themes are:* Earth System...
  
   (CICS)
• Cooperative Institute for Limnology and Ecosystems Research
  Cooperative Institute for Limnology and Ecosystems Research
  The Cooperative Institute for Limnology and Ecosystems Research fosters research collaborations between the National Oceanic and Atmospheric Administration /Office of Oceanic and Atmospheric Research Great Lakes Environmental Research Laboratory , Michigan State University and the University of...
  
   (CILER)
• Cooperative Institute for Marine and Atmospheric Studies
  Cooperative Institute for Marine and Atmospheric Studies
  The Cooperative Institute for Marine and Atmospheric Studies is a research institute of the University of Miami located in the Rosenstiel School of Marine and Atmospheric Science...
  
   (CIMAS)
• Cooperative Institute for Mesoscale Meteorological Studies
  Cooperative Institute for Mesoscale Meteorological Studies
  The Cooperative Institute for Mesoscale Meteorological Studies provides a mechanism to link the scientific and technical resources of the National Oceanic and Atmospheric Administration / Office of Oceanic and Atmospheric Research and the University of Oklahoma to create a center of research...
  
   (CIMMS)
• Cooperative Institute for Research in Environmental Sciences
  Cooperative Institute for Research in Environmental Sciences
  The Cooperative Institute for Research in Environmental Sciences is a research institute that is sponsored jointly by the National Oceanic and Atmospheric Administration /Office of Oceanic and Atmospheric Research and the University of Colorado at Boulder.- Quick facts :* Established in 1967 as...
  
   (CIRES)
• Cooperative Institute for Research in the Atmosphere
  Cooperative Institute for Research in the Atmosphere
  The Cooperative Institute for Research in the Atmosphere provides a mechanism to link the scientific and technical resources of the National Oceanic and Atmospheric Administration /Office of Oceanic and Atmospheric Research and Colorado State University.The CIRA research themes are:* Global and...
  
   (CIRA)
• corona (meteorology)
  Corona (meteorology)
  In meteorology, a corona is produced by the diffraction of light from either the Sun or the Moon by individual small water droplets of a cloud....
  
  
• COSMIC (Constellation Observing System for Meteorology, Ionosphere, and Climate)
• Cosmic Anisotropy Telescope
  Cosmic Anisotropy Telescope
  The Cosmic Anisotropy Telescope CAT was a three-element interferometer for cosmic microwave background radiation observations at 13 to 17 GHz, based at the Mullard Radio Astronomy Observatory. In 1995, it was the first instrument to measure small-scale structure in the cosmic microwave background...
  
   (CAT)
• (Cosmic Background Explorer) COBE
  COBE
  The COsmic Background Explorer , also referred to as Explorer 66, was a satellite dedicated to cosmology. Its goals were to investigate the cosmic microwave background radiation of the universe and provide measurements that would help shape our understanding of the cosmos.This work provided...
  
   ("to investigate the cosmic background radiation" etc.)
• cosmic microwave background experiments
  Cosmic microwave background experiments
  There have been a variety of experiments to measure the Cosmic microwave background radiation anisotropies and polarization since its first observation in 1964 by Penzias and Wilson. These include a mix of ground-, balloon- and space-based receivers...
  
  
• cosmic microwave background radiation
  Cosmic microwave background radiation
  In cosmology, cosmic microwave background radiation is thermal radiation filling the observable universe almost uniformly....
  
   (CMB) (CMBR) (CBR) (MBR)
• cosmic noise
  Cosmic noise
  Cosmic noise and galactic radio noise is random noise that originates outside the Earth's atmosphere. It can be detected and heard on radio receivers.- Elaboration :Cosmic noise characteristics are similar to those of thermal noise...
  
  
• cosmic ray
  Cosmic ray
  Cosmic rays are energetic charged subatomic particles, originating from outer space. They may produce secondary particles that penetrate the Earth's atmosphere and surface. The term ray is historical as cosmic rays were thought to be electromagnetic radiation...
  
   (see under Lightning)
• Cosmochemical Periodic Table of the Elements in the Solar System
• cosmochemistry
  Cosmochemistry
  Cosmochemistry or chemical cosmology is the study of the chemical composition of matter in the universe and the processes that led to those compositions. This is done primarily through the study of the chemical composition of meteorites and other physical samples...
  
  
• cumulonimbus cloud
  Cumulonimbus cloud
  Cumulonimbus is a towering vertical cloud that is very tall, dense, and involved in thunderstorms and other inclement weather. Cumulonimbus originates from Latin: Cumulus "Heap" and nimbus "rain". It is a result of atmospheric instability. These clouds can form alone, in clusters, or along a cold...
  
   (see under Effects)
• (cumulonimbus with mammatus: see) mammatus cloud
  Mammatus cloud
  Mammatus, also known as mammatocumulus , is a meteorological term applied to a cellular pattern of pouches hanging underneath the base of a cloud...
  
  
• (cumulonimbus with pileus: see) pileus (meteorology)
  Pileus (meteorology)
  A pileus , also called scarf cloud or cap cloud, is a small, horizontal cloud that can appear above a cumulus or cumulonimbus cloud, giving the parent cloud a characteristic "hoodlike" appearance. Pilei tend to change shape rapidly. They are formed by strong updrafts acting upon moist air at lower...
  
  
• cumulus castellanus cloud
• cumulus cloud
  Cumulus cloud
  Cumulus clouds are a type of cloud with noticeable vertical development and clearly defined edges. Cumulus means "heap" or "pile" in Latin. They are often described as "puffy" or "cotton-like" in appearance. Cumulus clouds may appear alone, in lines, or in clusters...
  
  
• cumulus congestus cloud
• cumulus humilis cloud
  Cumulus humilis cloud
  Cumulus humilis is a low to middle cloud with small vertical extent that is commonly referred to as "fair weather cumulus". In hot countries and over mountainous terrain these clouds occur at up to 6000 meters altitude, though elsewhere they are typically found lower.They are formed by rising warm...
  
  
• cumulus mediocris cloud
  Cumulus mediocris cloud
  Cumulus mediocris is a low to middle level cloud with some vertical extent of the genus cumulus, larger in vertical development than Cumulus humilis. It may or may not show the cauliflower form characteristic of cumulus clouds...
  
  
• (cup anemometer: see) anemometer
  Anemometer
  An anemometer is a device for measuring wind speed, and is a common weather station instrument. The term is derived from the Greek word anemos, meaning wind, and is used to describe any airspeed measurement instrument used in meteorology or aerodynamics...
  
   (see under Cup anemometers)
• current solar income
  Current solar income
  The current solar income of the Earth, or an ecozone or ecoregion or any area, is the amount of solar energy that falls on it as sunlight. This is thought important in some branches of green economics, as the ultimate measure of renewable energy....
  
  
• cyclone
  Cyclone
  In meteorology, a cyclone is an area of closed, circular fluid motion rotating in the same direction as the Earth. This is usually characterized by inward spiraling winds that rotate anticlockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere of the Earth. Most large-scale...
  
  
• cyclone furnace
  Cyclone furnace
  A cyclone furnace is a type of coal combustor commonly used in large industrial boilers.-Background:Developed in the early 1942 by Babcock & Wilcox to take advantage of coal grades not suitable for pulverized coal combustion, cyclone furnaces feed coal in a spiral manner into a combustion chamber...
  
   (a type of coal combustor)
• (cyclone preparedness: see) hurricane preparedness
  Hurricane preparedness
  Hurricane preparedness encompasses the actions and planning taken before a tropical cyclone strikes to mitigate damage and injury from the storm...
  
  
• cyclonic separation
  Cyclonic separation
  Cyclonic separation is a method of removing particulates from an air, gas or liquid stream, without the use of filters, through vortex separation. Rotational effects and gravity are used to separate mixtures of solids and fluids...
  
   (method of removing particles from an air or gas stream)

D

• D region
  D region
  The D region is the portion of the ionosphere that exists approximately 50 to 95 km above the surface of the Earth.Note: Attenuation of radio waves, caused by ionospheric free-electron density generated by solar radiation, is pronounced during daylight hours. Because solar radiation is not...
  
   (in the atmosphere)
• Darrieus wind turbine
  Darrieus wind turbine
  The Darrieus wind turbine is a type of vertical axis wind turbine used to generate electricity from the energy carried in the wind. The turbine consists of a number of aerofoils usually—but not always—vertically mounted on a rotating shaft or framework...
  
  
• dawn
  Dawn
  Dawn is the time that marks the beginning of the twilight before sunrise. It is recognized by the presence of weak sunlight, while the sun itself is still below the horizon...
  
  
• dBZ (meteorology)
  DBZ (meteorology)
  dBZ stands for decibels of Z. It is a meteorological measure of equivalent reflectivity of a radar signal reflected off a remote object. The reference level for Z is 1 mm6 m−3, which is equal to 1 μm3...
  
  
• degree (temperature)
  Degree (temperature)
  The term degree is used in several scales of temperature. The symbol ° is usually used, followed by the initial letter of the unit, for example “°C” for degree Celsius...
  
  
• deicing
  Deicing
  For snow and ice control on roadways and similar facilities, see Snow removalDe-icing is defined as removal of snow, ice or frost from a surface...
  
  
• dendroclimatology
  Dendroclimatology
  Dendroclimatology is the science of determining past climates from trees . Tree rings are wider when conditions favor growth, narrower when times are difficult. Other properties of the annual rings, such as maximum latewood density have been shown to be better proxies than simple ring width...
  
   ("extracting past climate information from information in trees")
• density altitude
  Density altitude
  Density altitude is the altitude in the International Standard Atmosphere at which the air density would be equal to the actual air density at the place of observation, or, in other words, the height when measured in terms of the density of the air rather than the distance from the ground...
  
  
• deposition (physics)
  Deposition (physics)
  Deposition is a process in which gas transforms into solid . The reverse of deposition is sublimation.One example of deposition is the process by which, in sub-freezing air, water vapor changes directly to ice without first becoming a liquid...
  
  
• (depression [meteorology]: see) low pressure area
  Low pressure area
  A low-pressure area, or "low", is a region where the atmospheric pressure at sea level is below that of surrounding locations. Low-pressure systems form under areas of wind divergence which occur in upper levels of the troposphere. The formation process of a low-pressure area is known as...
  
  
• derecho
  Derecho
  A derecho is a widespread and long-lived, violent convectively induced straight-line windstorm that is associated with a fast-moving band of severe thunderstorms in the form of a squall line usually taking the form of a bow echo...
  
   (see also List of derecho events)
• dew
  Dew
  [Image:Dew on a flower.jpg|right|220px|thumb|Some dew on an iris in Sequoia National Park]]Dew is water in the form of droplets that appears on thin, exposed objects in the morning or evening...
  
  
• dew point
  Dew point
  The dew point is the temperature to which a given parcel of humid air must be cooled, at constant barometric pressure, for water vapor to condense into liquid water. The condensed water is called dew when it forms on a solid surface. The dew point is a saturation temperature.The dew point is...
  
   (dewpoint)
• disdrometer
  Disdrometer
  A disdrometer is an instrument used to measure the drop size distribution and velocity of falling hydrometeors. Some disdrometers can distinguish between rain, graupel, and hail....
  
  
• downwelling
  Downwelling
  Downwelling is the process of accumulation and sinking of higher density material beneath lower density material, such as cold or saline water beneath warmer or fresher water or cold air beneath warm air. It is the sinking limb of a convection cell. Upwelling is the opposite process and together...
  
  
• drizzle
  Drizzle
  Drizzle is a light rain precipitation consisting of liquid water drops smaller than those of rain, and generally smaller than 0.5 mm in diameter. Drizzle is normally produced by low stratiform clouds and stratocumulus clouds. Precipitation rates due to drizzle are on the order of a millimetre...
  
  
• drought
  Drought
  A drought is an extended period of months or years when a region notes a deficiency in its water supply. Generally, this occurs when a region receives consistently below average precipitation. It can have a substantial impact on the ecosystem and agriculture of the affected region...
  
  
• dry line
  Dry line
  A dry line separates moist air from the Gulf of Mexico and dry desert air from the south-western states . The dry line is an important factor in severe weather frequency in the Great Plains of North America...
  
   (dew point line)
• dry season
  Dry season
  The dry season is a term commonly used when describing the weather in the tropics. The weather in the tropics is dominated by the tropical rain belt, which oscillates from the northern to the southern tropics over the course of the year...
  
  
• dusk
  Dusk
  Dusk is the beginning of darkness in the evening, and occurs after twilight, when the sky generally remains bright and blue. Civil dusk is when the earth has rotated enough that the center of the sun is at 6° below the local horizon...
  
  

E

• Earth's atmosphere
  Earth's atmosphere
  The atmosphere of Earth is a layer of gases surrounding the planet Earth that is retained by Earth's gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention , and reducing temperature extremes between day and night...
  
  
• Earth's magnetic field
  Earth's magnetic field
  Earth's magnetic field is the magnetic field that extends from the Earth's inner core to where it meets the solar wind, a stream of energetic particles emanating from the Sun...
  
  
• economics of global warming
  Economics of global warming
  -Definitions:In this article, the phrase “climate change” is used to describe a change in the climate, measured in terms of its statistical properties, e.g., the global mean surface temperature. In this context, “climate” is taken to mean the average weather. Climate can change over period of time...
  
  
• effect of Hurricane Katrina on New Orleans
  Effect of Hurricane Katrina on New Orleans
  The effects of Hurricane Katrina in New Orleans have been long-lasting. As the center of Katrina passed South-east of New Orleans on August 29, 2005, winds downtown were in the Category 3 range with frequent intense gusts and tidal surge. Hurricane force winds were experienced throughout the...
  
   (see also Hurricane Katrina effects by region
  Hurricane Katrina effects by region
  This article covers the Hurricane Katrina effects by region, within the United States and Canada. The effects of Hurricane Katrina, in August 2005, were catastrophic and widespread. It was one of the deadliest natural disasters in U.S. history, leaving 1836 people dead, and a further 705 missing....
  
  )
• effect of sun angle on climate
  Effect of sun angle on climate
  The amount of heat energy received at any location on the globe is a direct effect of sun angle on climate, as the angle at which sunlight strikes the Earth varies by location, time of day, and season due to the Earth's orbit around the sun and the Earth's rotation around its tilted axis...
  
  
• eolian processes
  Eolian processes
  Aeolian processes pertain to the activity of the winds and more specifically, to the winds' ability to shape the surface of the Earth and other planets. Winds may erode, transport, and deposit materials, and are effective agents in regions with sparse vegetation and a large supply of...
  
  
• equator
  Equator
  An equator is the intersection of a sphere's surface with the plane perpendicular to the sphere's axis of rotation and containing the sphere's center of mass....
  
   (see under Equatorial climate)
• European Centre for Medium-Range Weather Forecasts
  European Centre for Medium-Range Weather Forecasts
  The European Centre for Medium-Range Weather Forecasts is an independent intergovernmental organisation supported by 19 European Member States and 15 Co-operating States...
  
   (ECMWF)
• European Climate Change Programme
  European Climate Change Programme
  The European Climate Change Programme was launched in June 2000 by the European Union's European Commission, toward avoiding dangerous climate change....
  
   (ECCP)
• European emission standards
  European emission standards
  European emission standards define the acceptable limits for exhaust emissions of new vehicles sold in EU member states. The emission standards are defined in a series of European Union directives staging the progressive introduction of increasingly stringent standards.Currently, emissions of...
  
   (for motor vehicles)
• European windstorm
  European windstorm
  A European windstorm is a severe cyclonic windstorm associated with areas of low atmospheric pressure that track across the North Atlantic towards northwestern Europe. They are most common in the winter months...
  
  
• evaporation
  Evaporation
  Evaporation is a type of vaporization of a liquid that occurs only on the surface of a liquid. The other type of vaporization is boiling, which, instead, occurs on the entire mass of the liquid....
  
  
• evaporative cooler
• evaporative cooling
• evaporite
  Evaporite
  Evaporite is a name for a water-soluble mineral sediment that result from concentration and crystallization by evaporation from an aqueous solution. There are two types of evaporate deposits, marine which can also be described as ocean deposits, and non-marine which are found in standing bodies of...
  
   (a mineral sediment resulting from evaporation of saline water)
• evapotranspiration
  Evapotranspiration
  Evapotranspiration is a term used to describe the sum of evaporation and plant transpiration from the Earth's land surface to atmosphere. Evaporation accounts for the movement of water to the air from sources such as the soil, canopy interception, and waterbodies...
  
   (ET) (sum of evaporation and plant transpiration)
• exhaust gas recirculation
  Exhaust gas recirculation
  In internal combustion engines, exhaust gas recirculation is a nitrogen oxide emissions reduction technique used in petrol/gasoline and diesel engines. EGR works by recirculating a portion of an engine's exhaust gas back to the engine cylinders. In a gasoline engine, this inert exhaust...
  
   (EGR) (exhaust gas recycling)
• exosphere
  Exosphere
  The exosphere is the uppermost layer of Earth's atmosphere. In the exosphere, an upward travelling molecule moving fast enough to attain escape velocity can escape to space with a low chance of collisions; if it is moving below escape velocity it will be prevented from escaping from the celestial...
  
   (layer of atmosphere)
• extratropical cyclone
  Extratropical cyclone
  Extratropical cyclones, sometimes called mid-latitude cyclones or wave cyclones, are a group of cyclones defined as synoptic scale low pressure weather systems that occur in the middle latitudes of the Earth having neither tropical nor polar characteristics, and are connected with fronts and...
  
   (mid-latitude cyclone)
• extreme weather
  Extreme weather
  Extreme weather includes weather phenomena that are at the extremes of the historical distribution, especially severe or unseasonal weather. The most commonly used definition of extreme weather is based on an event's climatological distribution. Extreme weather occurs only 5% or less of the time...
  
  
• extremes on Earth
  Extremes on Earth
  This article describes extreme locations on Earth. Entries listed in bold are Earth-wide extremes.-Extreme elevations and temperatures per continent:This article describes extreme locations on Earth. Entries listed in bold are Earth-wide extremes....
  
  

F

• fog
  Fog
  Fog is a collection of water droplets or ice crystals suspended in the air at or near the Earth's surface. While fog is a type of stratus cloud, the term "fog" is typically distinguished from the more generic term "cloud" in that fog is low-lying, and the moisture in the fog is often generated...
  
  
• forensic meteorology
  Forensic meteorology
  Forensic meteorology is the process of reconstructing weather events for a certain location. This is done by acquiring local weather reports, radar and satellite images, and eyewitness accounts. Forensic meteorology is most often used in court cases for either insurance companies or a murder...
  
  
• freezing rain
  Freezing rain
  Freezing rain is the name given to rain that falls when surface temperatures are below freezing. The raindrops become supercooled while passing through a sub-freezing layer of air, many hundred feet , just above the surface, and then freeze upon impact with any object they encounter. The resulting...
  
  
• (front [meteorology]: see) surface weather analysis
  Surface weather analysis
  Surface weather analysis is a special type of weather map that provides a view of weather elements over a geographical area at a specified time based on information from ground-based weather stations...
  
  
• frost
  Frost
  Frost is the solid deposition of water vapor from saturated air. It is formed when solid surfaces are cooled to below the dew point of the adjacent air as well as below the freezing point of water. Frost crystals' size differ depending on time and water vapour available. Frost is also usually...
  
  
• frost creep (frost heave)
• frost flowers
  Frost flowers
  Frost flowers is the name commonly given to a condition in which thin layers of ice are extruded from long-stemmed plants in autumn or early winter...
  
   (frost castles) (ice castles) (ice ribbons) (ice blossoms)
• frost heaving
  Frost heaving
  Frost heaving results from ice forming beneath the surface of soil during freezing conditions in the atmosphere. The ice grows in the direction of heat loss , starting at the freezing front or boundary in the soil...
  
   (frost heave)
• frost law
  Frost law
  Frost laws are seasonal restrictions on traffic weight limits and speeds on roadways subject to thaw weakening.In climates that experience below-freezing temperatures, damage to roads from thaw-weakening have led to many U.S...
  
  
• frost line
  Frost line
  The frost line—also known as frost depth or freezing depth—is most commonly the depth to which the groundwater in soil is expected to freeze. The frost depth depends on the climatic conditions of an area, the heat transfer properties of the soil and adjacent materials, and on nearby heat sources...
  
  
• (frost point: see) dew point
  Dew point
  The dew point is the temperature to which a given parcel of humid air must be cooled, at constant barometric pressure, for water vapor to condense into liquid water. The condensed water is called dew when it forms on a solid surface. The dew point is a saturation temperature.The dew point is...
  
   (dewpoint)
• frostbite
  Frostbite
  Frostbite is the medical condition where localized damage is caused to skin and other tissues due to extreme cold. Frostbite is most likely to happen in body parts farthest from the heart and those with large exposed areas...
  
  
• Fujita scale
  Fujita scale
  The Fujita scale , or Fujita-Pearson scale, is a scale for rating tornado intensity, based primarily on the damage tornadoes inflict on human-built structures and vegetation...
  
   (for measuring tornadoes)
• fulgurite
  Fulgurite
  Fulgurites are natural hollow glass tubes formed in quartzose sand, or silica, or soil by lightning strikes. They are formed when lightning with a temperature of at least instantaneously melts silica on a conductive surface and fuses grains together; the fulgurite tube is the cooled product...
  
  
• (full lunar eclipse: see) lunar eclipse
  Lunar eclipse
  A lunar eclipse occurs when the Moon passes behind the Earth so that the Earth blocks the Sun's rays from striking the Moon. This can occur only when the Sun, Earth, and Moon are aligned exactly, or very closely so, with the Earth in the middle. Hence, a lunar eclipse can only occur the night of a...
  
  
• full-spectrum
  Full-spectrum
  Full-spectrum light is light that covers the electromagnetic spectrum from infrared through near-ultraviolet, or all wavelengths that are useful to plant or animal life; in particular, sunlight is considered full spectrum, even though the solar spectral distribution reaching Earth changes with time...
  
   light
• funnel cloud
  Funnel cloud
  A funnel cloud is a funnel-shaped cloud of condensed water droplets, associated with a rotating column of wind and extending from the base of a cloud but not reaching the ground or a water surface. A funnel cloud is usually visible as a cone-shaped or needle like protuberance from the main cloud...
  
   (related to a tornado)

G

• galactic cosmic ray
  Galactic cosmic ray
  Galactic cosmic rays are cosmic rays that have their origin inside our Galaxy. GCRs are high-energy charged particles, and are usually protons, electrons, and fully ionized nuclei of light elements...
  
   (GCR)
• gale
  Gale
  A gale is a very strong wind. There are conflicting definitions of how strong a wind must be to be considered a gale. The U.S. government's National Weather Service defines a gale as 34–47 knots of sustained surface winds. Forecasters typically issue gale warnings when winds of this strength are...
  
  
• gale warning
  Gale warning
  A gale warning is a warning issued by weather services in maritime locations about the existence of winds of gale force or above or the imminent occurrence of gales at sea...
  
  
• Galileo thermometer
  Galileo thermometer
  A Galileo thermometer , named after Italian physicist Galileo Galilei, is a thermometer made of a sealed glass cylinder containing a clear liquid and a series of objects whose densities are such that they rise or fall as the temperature changes...
  
   (Galilean thermometer)
• Galveston, Texas
  Galveston, Texas
  Galveston is a coastal city located on Galveston Island in the U.S. state of Texas. , the city had a total population of 47,743 within an area of...
  
   (see under The 1900 Storm)
• Galveston Hurricane of 1900
  Galveston Hurricane of 1900
  The Hurricane of 1900 made landfall on the city of Galveston in the U.S. state of Texas, on September 8, 1900.It had estimated winds of at landfall, making it a Category 4 storm on the Saffir-Simpson Hurricane Scale...
  
   (in the US)
• gas balloon
  Gas balloon
  A gas balloon is any balloon that stays aloft due to being filled with a gas less dense than air or lighter than air . A gas balloon may also be called a Charlière for its inventor, the Frenchman Jacques Charles. Today, familiar gas balloons include large blimps and small rubber party balloons...
  
   (see under Gas balloons today)
• gas flare
  Gas flare
  A gas flare, alternatively known as a flare stack, is an elevated vertical conveyance found accompanying the presence of oil wells, gas wells, rigs, refineries, chemical plants, natural gas plants, and landfills....
  
   (flare stack)
• (gas warfare: see) chemical warfare
  Chemical warfare
  Chemical warfare involves using the toxic properties of chemical substances as weapons. This type of warfare is distinct from Nuclear warfare and Biological warfare, which together make up NBC, the military acronym for Nuclear, Biological, and Chemical...
  
  

Ge-Gk

• geomagnetic storm
  Geomagnetic storm
  A geomagnetic storm is a temporary disturbance of the Earth's magnetosphere caused by a disturbance in the interplanetary medium. A geomagnetic storm is a major component of space weather and provides the input for many other components of space weather...
  
  
• (geomagnetism: see) Earth's magnetic field
  Earth's magnetic field
  Earth's magnetic field is the magnetic field that extends from the Earth's inner core to where it meets the solar wind, a stream of energetic particles emanating from the Sun...
  
  
• geospatial technology (Spatial Information Technology)
• Geostationary Operational Environmental Satellite
  Geostationary Operational Environmental Satellite
  The Geostationary Satellite system, operated by the United States National Environmental Satellite, Data, and Information Service , supports weather forecasting, severe storm tracking, and meteorology research. Spacecraft and ground-based elements of the system work together to provide a continuous...
  
   (GOES) (a program of the US)
• geostatistics
  Geostatistics
  Geostatistics is a branch of statistics focusing on spatial or spatiotemporal datasets. Developed originally to predict probability distributions of ore grades for mining operations, it is currently applied in diverse disciplines including petroleum geology, hydrogeology, hydrology, meteorology,...
  
  
• geostrophic wind
  Geostrophic wind
  The geostrophic wind is the theoretical wind that would result from an exact balance between the Coriolis effect and the pressure gradient force. This condition is called geostrophic balance. The geostrophic wind is directed parallel to isobars . This balance seldom holds exactly in nature...
  
  
• Global Atmosphere Watch
  Global Atmosphere Watch
  The Global Atmosphere Watch is a worldwide system established by the World Meteorological Organization a United Nations agency to monitor trends in the Earth's atmosphere...
  
   (GAW)
• greenhouse effect
  Greenhouse effect
  The greenhouse effect is a process by which thermal radiation from a planetary surface is absorbed by atmospheric greenhouse gases, and is re-radiated in all directions. Since part of this re-radiation is back towards the surface, energy is transferred to the surface and the lower atmosphere...
  
  
• greenhouse gas
  Greenhouse gas
  A greenhouse gas is a gas in an atmosphere that absorbs and emits radiation within the thermal infrared range. This process is the fundamental cause of the greenhouse effect. The primary greenhouse gases in the Earth's atmosphere are water vapor, carbon dioxide, methane, nitrous oxide, and ozone...
  
   (GHG)
• growing degree day
  Growing degree day
  Growing degree days , also called growing degree units , are a heuristic tool in phenology. GDD are a measure of heat accumulation used by horticulturists, gardeners, and farmers to predict plant and pest development rates such as the date that a flower will bloom or a crop reach...
  
   (GDD)
• growing season
  Growing season
  In botany, horticulture, and agriculture the growing season is the period of each year when native plants and ornamental plants grow; and when crops can be grown....
  
  

H

• hail
  Hail
  Hail is a form of solid precipitation. It consists of balls or irregular lumps of ice, each of which is referred to as a hail stone. Hail stones on Earth consist mostly of water ice and measure between and in diameter, with the larger stones coming from severe thunderstorms...
  
  
• halo (optical phenomenon)
  Halo (optical phenomenon)
  A halo from Greek ἅλως; also known as a nimbus, icebow or gloriole) is an optical phenomenon produced by ice crystals creating colored or white arcs and spots in the sky. Many are near the sun or moon but others are elsewhere and even in the opposite part of the sky...
  
  
• haze
  Haze
  Haze is traditionally an atmospheric phenomenon where dust, smoke and other dry particles obscure the clarity of the sky. The World Meteorological Organization manual of codes includes a classification of horizontal obscuration into categories of fog, ice fog, steam fog, mist, haze, smoke, volcanic...
  
  
• heat
  Heat
  In physics and thermodynamics, heat is energy transferred from one body, region, or thermodynamic system to another due to thermal contact or thermal radiation when the systems are at different temperatures. It is often described as one of the fundamental processes of energy transfer between...
  
  
• (heat budget: see) radiation budget
• (heat equator: see) thermal equator
  Thermal equator
  The thermal equator is a belt encircling the Earth, defined by the set of locations having the highest mean annual temperature at each longitude around the globe...
  
  
• (heat lightning: see) lightning
  Lightning
  Lightning is an atmospheric electrostatic discharge accompanied by thunder, which typically occurs during thunderstorms, and sometimes during volcanic eruptions or dust storms...
  
  
• heat wave
  Heat wave
  A heat wave is a prolonged period of excessively hot weather, which may be accompanied by high humidity. There is no universal definition of a heat wave; the term is relative to the usual weather in the area...
  
  
• heating degree day
  Heating degree day
  Heating degree day is a measurement designed to reflect the demand for energy needed to heat a home or business. It is derived from measurements of outside air temperature. The heating requirements for a given structure at a specific location are considered to be directly proportional to the...
  
   (HDD)
• (Heaviside layer) Kennelly–Heaviside layer (E region) (in the atmosphere)
• Heavy snow warning
  Heavy Snow Warning
  A Heavy snow warning was a weather warning issued by the National Weather Service of the United States during times when a high rate of snowfall was occurring or was forecast...
  
  
• heliostat
  Heliostat
  A heliostat is a device that includes a mirror, usually a plane mirror, which turns so as to keep reflecting sunlight toward a predetermined target, compensating for the sun's apparent motions in the sky. The target may be a physical object, distant from the heliostat, or a direction in space...
  
  
• High Frequency Active Auroral Research Program
  High Frequency Active Auroral Research Program
  The High Frequency Active Auroral Research Program is an ionospheric research program jointly funded by the U.S. Air Force, the U.S. Navy, the University of Alaska, and the Defense Advanced Research Projects Agency ....
  
   (HAARP)
• high pressure area
  High pressure area
  A high-pressure area is a region where the atmospheric pressure at the surface of the planet is greater than its surrounding environment. Winds within high-pressure areas flow outward due to the higher density air near their center and friction with land...
  
  
• High Resolution Fly's Eye Cosmic Ray Detector
  High Resolution Fly's Eye Cosmic Ray Detector
  The High Resolution Fly's Eye or HiRes detector was an ultra-high-energy cosmic ray observatory that operated in the western Utah desert from May 1997 until April 2006. HiRes utilized the atmospheric fluorescence technique that was pioneered by the Utah group first in tests at the Volcano Ranch...
  
  
• high-altitude airship
  High-altitude airship
  The United States Department of Defense Missile Defense Agency contracted Lockheed Martin to construct a high-altitude airship to enhance its Ballistic Missile Defense System ....
  
   (HAA)
• humid continental climate
  Humid continental climate
  A humid continental climate is a climatic region typified by large seasonal temperature differences, with warm to hot summers and cold winters....
  
  
• humid subtropical climate
  Humid subtropical climate
  A humid subtropical climate is a climate zone characterized by hot, humid summers and mild to cool winters...
  
  
• (humidex) heat index
  Heat index
  The heat index is an index that combines air temperature and relative humidity in an attempt to determine the human-perceived equivalent temperature — how hot it feels, termed the felt air temperature. The human body normally cools itself by perspiration, or sweating, which evaporates and carries...
  
   (HI)
• humidity
  Humidity
  Humidity is a term for the amount of water vapor in the air, and can refer to any one of several measurements of humidity. Formally, humid air is not "moist air" but a mixture of water vapor and other constituents of air, and humidity is defined in terms of the water content of this mixture,...
  
  
• HurriQuake
  HurriQuake
  The HurriQuake nail is a construction nail designed by Ed Sutt for Bostitch, a division of Stanley Works, and patented in 2004. The features of the nail are designed primarily to provide more structural integrity for a building, especially against the forces of hurricanes and earthquakes.-Features...
  
   nail (for resisting hurricanes and earthquakes)
• (hydrologic cycle) water cycle
  Water cycle
  The water cycle, also known as the hydrologic cycle or H2O cycle, describes the continuous movement of water on, above and below the surface of the Earth. Water can change states among liquid, vapor, and solid at various places in the water cycle...
  
  
• hydrological phenomenon
  Hydrological phenomenon
  A hydrological phenomenon, or hydrologic phenomenon, is an observable movement of water within the water cycle. Hydrological phenomena are studied within the field of hydrology, and include:* precipitation, including rain and snow* floods* droughts...
  
  
• hydrology
  Hydrology
  Hydrology is the study of the movement, distribution, and quality of water on Earth and other planets, including the hydrologic cycle, water resources and environmental watershed sustainability...
  
  
• hydrosphere
  Hydrosphere
  A hydrosphere in physical geography describes the combined mass of water found on, under, and over the surface of a planet....
  
  
• hygrometer
  Hygrometer
  A hygrometer is an instrument used for measuring the moisture content in the environmental air, or humidity. Most measurement devices usually rely on measurements of some other quantity such as temperature, pressure, mass or a mechanical or electrical change in a substance as moisture is absorbed...
  
   (different from hydrometer
  Hydrometer
  A hydrometer is an instrument used to measure the specific gravity of liquids; that is, the ratio of the density of the liquid to the density of water....
  
  )
• hypercane
  Hypercane
  A hypercane is a hypothetical class of extreme hurricane that could form if ocean temperatures reached around , which is warmer than the warmest ocean temperature ever recorded. Such an increase could be caused by a large asteroid or comet impact, a large volcanic, supervolcanic eruption, or very...
  
   ("hypothetical class of hurricane")

I

• ice
  Ice
  Ice is water frozen into the solid state. Usually ice is the phase known as ice Ih, which is the most abundant of the varying solid phases on the Earth's surface. It can appear transparent or opaque bluish-white color, depending on the presence of impurities or air inclusions...
  
  
• Ice Accretion Indicator
  Ice Accretion Indicator
  The Ice Accretion Indicator is an L-shaped piece of aluminium 38 cm long by 5 cm wide. It is used to indicate the formation of ice, frost or the presence of freezing rain or freezing drizzle....
  
  
• ice age
  Ice age
  An ice age or, more precisely, glacial age, is a generic geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in the presence or expansion of continental ice sheets, polar ice sheets and alpine glaciers...
  
  
• ice storm
  Ice storm
  An ice storm is a type of winter storm characterized by freezing rain, also known as a glaze event or in some parts of the United States as a silver thaw. The U.S. National Weather Service defines an ice storm as a storm which results in the accumulation of at least of ice on exposed surfaces...
  
  
• Ice Storm Warning
  Ice Storm Warning
  An Ice Storm Warning is issued by the National Weather Service of the United States when freezing rain produces a significant and possibly damaging accumulation of ice...
  
  
• illuminance
  Illuminance
  In photometry, illuminance is the total luminous flux incident on a surface, per unit area. It is a measure of the intensity of the incident light, wavelength-weighted by the luminosity function to correlate with human brightness perception. Similarly, luminous emittance is the luminous flux per...
  
  
• impact winter
  Impact winter
  An impact winter is a period of prolonged cold weather caused by the impact on the Earth of a large asteroid or comet. If such an impact occurred on land or the floor of a shallow sea, it could cause large amounts of dust or ash to be thrown into the Earth's atmosphere, blocking the Sun's light...
  
  
• impluvium
  Impluvium
  The impluvium is the sunken part of the atrium in a Greek or Roman house . Designed to carry away the rainwater coming through the compluvium of the roof, it is usually made of marble and placed about 30 cm below the floor of the atrium.The name is also used for a type of dwelling typical of...
  
  
• in situ
  In situ
  In situ is a Latin phrase which translated literally as 'In position'. It is used in many different contexts.-Aerospace:In the aerospace industry, equipment on board aircraft must be tested in situ, or in place, to confirm everything functions properly as a system. Individually, each piece may...
  
   (see under Earth and atmospheric sciences)
• incidental radiator
• India Meteorological Department
  India Meteorological Department
  The India Meteorological Department , also referred to as the Met Office, is an agency of the Ministry of Earth Sciences of the Government of India. It is the principal agency responsible for meteorological observations, weather forecasting and seismology...
  
  
• Indian summer
  Indian summer
  An Indian summer is a meteorological phenomenon that occurs in the autumn. It refers to a period of considerably above normal temperatures, accompanied by dry and hazy conditions, usually after there has been a killing frost...
  
  
• infrared
  Infrared
  Infrared light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.74 micrometres , and extending conventionally to 300 µm...
  
   (IR) radiation (see under Meteorology)
• insolation
  Insolation
  Insolation is a measure of solar radiation energy received on a given surface area in a given time. It is commonly expressed as average irradiance in watts per square meter or kilowatt-hours per square meter per day...
  
  
• instrument meteorological conditions
  Instrument meteorological conditions
  Instrument meteorological conditions is an aviation flight category that describes weather conditions that require pilots to fly primarily by reference to instruments, and therefore under Instrument Flight Rules , rather than by outside visual references under Visual Flight Rules . Typically, this...
  
   (IMG)
• instrumental temperature record
  Instrumental temperature record
  The instrumental temperature record shows fluctuations of the temperature of the global land surface and oceans. This data is collected from several thousand meteorological stations, Antarctic research stations and satellite observations of sea-surface temperature. Currently, the longest-running...
  
  
• intentional radiator
  Intentional radiator
  An intentional radiator is any device that is designed to produce radio waves on purpose.Radio transmitters of all kinds, including the garage door opener, cordless telephone, cellular phone, wireless video sender, wireless microphone, and many others fall into this category.-See also:* incidental...
  
  
• International Meteorological Organization
  International Meteorological Organization
  The International Meteorological Organization was the first organization formed with the purpose of exchanging weather information among the countries of the world. It was born from the realization that weather systems move across country boundaries and knowledge of pressure, temperature,...
  
   (IMO)
• International Temperature Scale of 1990
  International Temperature Scale of 1990
  The International Temperature Scale of 1990 is an equipment calibration standard for making measurements on the Kelvin and Celsius temperature scales. ITS–90 is an approximation of the thermodynamic temperature scale that facilitates the comparability and compatibility of temperature measurements...
  
   (ITS-90)
• International Terrestrial Reference System
  International Terrestrial Reference System
  The International Terrestrial Reference System describes procedures for creating reference frames suitable for use with measurements on or near the Earth's surface. This is done in much the same way that a physical standard might be described as a set of procedures for creating a realization of...
  
   (ITRS)
• Invest (meteorology)
  Invest (meteorology)
  An invest in meteorology is a designated area of disturbed weather that is being monitored for tropical cyclone development. Invests are designated by three separate forecast centers: the National Hurricane Center, Central Pacific Hurricane Center and Joint Typhoon Warning Center...
  
  
• ion wind
  Ion wind
  Ion wind, ionic wind, or coronal wind is a stream of ionized fluid generated by a strong electric field. Francis Hauksbee, curator of instruments for the Royal Society of London, made the earliest report of electric wind in 1709...
  
   (ion wind) (coronal wind)
• ionosonde
  Ionosonde
  An ionosonde, or chirpsounder, is a special radar for the examination of the ionosphere. An ionosonde consists of:* A high frequency transmitter, automatically tunable over a wide range...
  
   (chirpsounder)
• ionosphere
  Ionosphere
  The ionosphere is a part of the upper atmosphere, comprising portions of the mesosphere, thermosphere and exosphere, distinguished because it is ionized by solar radiation. It plays an important part in atmospheric electricity and forms the inner edge of the magnetosphere...
  
  
• ionospheric reflection
  Ionospheric reflection
  Ionospheric reflection is a bending, through a complex process involving reflection and refraction, of electromagnetic waves propagating in the ionosphere back toward the Earth....
  
  
• ionospheric sounding
  Ionospheric sounding
  In telecommunication and radio science, an ionospheric sounding is a technique that provides real-time data on high-frequency ionospheric-dependent radio propagation, using a basic system consisting of a synchronized transmitter and receiver....
  
  
• iron cycle
  Iron cycle
  In ecology or geoscience, the iron cycle is the biogeochemical cycle of iron through landforms, the atmosphere, and oceans. The iron cycle affects dust deposition and aerosol iron bioavailability..- References :...
  
  
• irradiance
  Irradiance
  Irradiance is the power of electromagnetic radiation per unit area incident on a surface. Radiant emittance or radiant exitance is the power per unit area radiated by a surface. The SI units for all of these quantities are watts per square meter , while the cgs units are ergs per square centimeter...
  
  
• irradiation
  Irradiation
  Irradiation is the process by which an object is exposed to radiation. The exposure can originate from various sources, including natural sources. Most frequently the term refers to ionizing radiation, and to a level of radiation that will serve a specific purpose, rather than radiation exposure to...
  
  
• isobar
• isochore
  Isochore
  Isochore may refer to:* an Isochoric process in thermodynamics* isochore...
  
   (in a thermodynamic
  Thermodynamics
  Thermodynamics is a physical science that studies the effects on material bodies, and on radiation in regions of space, of transfer of heat and of work done on or by the bodies or radiation...
  
   diagram)
• isodrosotherm
• isogon (meteorology)
• (isogram) contour line
  Contour line
  A contour line of a function of two variables is a curve along which the function has a constant value. In cartography, a contour line joins points of equal elevation above a given level, such as mean sea level...
  
   (level set
  Level set
  In mathematics, a level set of a real-valued function f of n variables is a set of the formthat is, a set where the function takes on a given constant value c....
  
  ) (isarithm)
• isohel
• isohume
• isohyet
• isohypse (in topography
  Topography
  Topography is the study of Earth's surface shape and features or those ofplanets, moons, and asteroids...
  
  )
• isotherm

L

• Laboratory for Atmospheric and Space Physics
  Laboratory for Atmospheric and Space Physics
  The Laboratory for Atmospheric and Space Physics is a research organization at the University of Colorado at Boulder. LASP is a research institute with over 100 research scientists ranging in fields from solar influences, to Earth's and other planetary atmospherics processes, space weather, space...
  
   (LASP)
• lake effect snow
  Lake effect snow
  Lake-effect snow is produced during cooler atmospheric conditions when cold winds move across long expanses of warmer lake water, providing energy and picking up water vapor which freezes and is deposited on the leeward shores...
  
   (a snowsquall)
• (lake surge: see) storm surge
  Storm surge
  A storm surge is an offshore rise of water associated with a low pressure weather system, typically tropical cyclones and strong extratropical cyclones. Storm surges are caused primarily by high winds pushing on the ocean's surface. The wind causes the water to pile up higher than the ordinary sea...
  
  
• land hemisphere
  Land hemisphere
  The land hemisphere, sometimes capitalised as the Land Hemisphere, is the hemisphere on the Earth containing the largest possible area of land. It is centered on or on ....
  
  
• land lighthouse
  Land lighthouse
  A land lighthouse is simply a lighthouse constructed to aid navigation over land, rather than water. Historically, they were constructed in areas of flatland where the featureless landscape and prevailing weather conditions might cause travellers to become easily disorientated and lost...
  
  
• lapse rate
  Lapse rate
  The lapse rate is defined as the rate of decrease with height for an atmospheric variable. The variable involved is temperature unless specified otherwise. The terminology arises from the word lapse in the sense of a decrease or decline; thus, the lapse rate is the rate of decrease with height and...
  
  
• lenticular cloud
  Lenticular cloud
  Lenticular clouds are stationary lens-shaped clouds that form at high altitudes, normally aligned perpendicular to the wind direction. Lenticular clouds can be separated into altocumulus standing lenticularis , stratocumulus standing lenticular , and cirrocumulus standing lenticular...
  
  
• life zone
  Life zone
  The Life Zone concept was developed by C. Hart Merriam in 1889 as a means of describing areas with similar plant and animal communities. Merriam observed that the changes in these communities with an increase in latitude at a constant elevation are similar to the changes seen with an increase in...
  
  
• lightning
  Lightning
  Lightning is an atmospheric electrostatic discharge accompanied by thunder, which typically occurs during thunderstorms, and sometimes during volcanic eruptions or dust storms...
  
  
• lightning rod
  Lightning rod
  A lightning rod or lightning conductor is a metal rod or conductor mounted on top of a building and electrically connected to the ground through a wire, to protect the building in the event of lightning...
  
   (lightning protector) (lightning finial)
• lightning safety
• (lightning storm) thunderstorm
  Thunderstorm
  A thunderstorm, also known as an electrical storm, a lightning storm, thundershower or simply a storm is a form of weather characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere known as thunder. The meteorologically assigned cloud type associated with the...
  
   (T-storm) (electrical storm)
• lightvessel
  Lightvessel
  A lightvessel, or lightship, is a ship which acts as a lighthouse. They are used in waters that are too deep or otherwise unsuitable for lighthouse construction...
  
   (lightship)
• line source
  Line source
  A line source is a source of air, noise, water contamination or electromagnetic radiation that emanates from a linear geometry...
  
   ("a source of air, noise, water contamination or electromagnetic radiation")
• (list of all-time high and low temperatures by state: see) U.S. state temperature extremes
  U.S. state temperature extremes
  The following table lists the highest and lowest temperatures recorded in each state in the United States, in both Fahrenheit and Celsius.The following table lists the highest and lowest temperatures recorded in each state in the United States, in both Fahrenheit and Celsius.The following table...
  
  
• list of basic earth science topics
• list of Category 5 Atlantic hurricanes
• list of Category 5 Pacific hurricanes
• list of cloud types
• list of coastal weather stations of the United Kingdom
• list of countries by carbon dioxide emissions
• list of countries by carbon dioxide emissions per capita
• list of countries by ratio of GDP to carbon dioxide emissions
• list of Earth observation satellites
• list of lighthouses and lightvessels
• list of meteorological phenomena
• list of most polluting power stations
• list of named tropical cyclones
• list of Northern Indian Ocean tropical cyclone seasons (see also :Category:North Indian cyclone seasons)
• List of derecho events
• list of notable tropical cyclones
• list of power outages
• list of scientific journals in earth and atmospheric sciences
• list of Solar Cycles (list of sunspot cycles)
• list of tornado-related deaths at schools
• list of weather instruments
• list of weather records
• low pressure area
  Low pressure area
  A low-pressure area, or "low", is a region where the atmospheric pressure at sea level is below that of surrounding locations. Low-pressure systems form under areas of wind divergence which occur in upper levels of the troposphere. The formation process of a low-pressure area is known as...
  
   (see same for "low-pressure cell")
• (lowest elevations: see) list of places on land with elevations below sea level
• (luminous pollution) light pollution
  Light pollution
  Light pollution, also known as photopollution or luminous pollution, is excessive or obtrusive artificial light.The International Dark-Sky Association defines light pollution as:...
  
   (photopollution)
• lunar phase
  Lunar phase
  A lunar phase or phase of the moon is the appearance of the illuminated portion of the Moon as seen by an observer, usually on Earth. The lunar phases change cyclically as the Moon orbits the Earth, according to the changing relative positions of the Earth, Moon, and Sun...
  
  

M

• magnetic storm
  Magnetic storm
  Magnetic storm can refer to:* A geomagnetic storm* Magnetic Storm , the title of a book of paintings by Roger Dean* Magnetic Storm , the title of an hourlong PBS NOVA documentary about Earth's changing magnetic fields...
  
   (geomagnetic storm)
• magnetopause
  Magnetopause
  The magnetopause is the abrupt boundary between a magnetosphere and the surrounding plasma. For planetary science, the magnetopause is the boundary between the planet’s magnetic field and the solar wind. The location of the magnetopause is determined by the balance between the pressure of the...
  
  
• magnetosheath
  Magnetosheath
  The magnetosheath is the region of space between the magnetopause and the bow shock of a planet's magnetosphere. The regularly organized magnetic field generated by the planet becomes weak and irregular in the magnetosheath due to interaction with the incoming solar wind, and is incapable of fully...
  
  
• magnetosphere
  Magnetosphere
  A magnetosphere is formed when a stream of charged particles, such as the solar wind, interacts with and is deflected by the intrinsic magnetic field of a planet or similar body. Earth is surrounded by a magnetosphere, as are the other planets with intrinsic magnetic fields: Mercury, Jupiter,...
  
  
• marine west coast climate (maritime climate) (oceanic climate
  Oceanic climate
  An oceanic climate, also called marine west coast climate, maritime climate, Cascadian climate and British climate for Köppen climate classification Cfb and subtropical highland for Köppen Cfb or Cwb, is a type of climate typically found along the west coasts at the middle latitudes of some of the...
  
  )
• Mars Climate Orbiter
  Mars Climate Orbiter
  The Mars Climate Orbiter was a 338 kilogram robotic space probe launched by NASA on December 11, 1998 to study the Martian climate, atmosphere, surface changes and to act as the communications relay in the Mars Surveyor '98 program, for Mars Polar Lander...
  
  
• Mars Radiation Environment Experiment
  Mars Radiation Environment Experiment
  The Martian Radiation Experiment, or MARIE was designed to measure the radiation environment of Mars using an energetic particle spectrometer as part of the science mission of the 2001 Mars Odyssey spacecraft...
  
   (Martian Radiation Experiment) (MARIE)
• maximum sustained wind
  Maximum sustained wind
  The maximum sustained winds associated with a tropical cyclone are a common indicator of the intensity of the storm. Within a mature tropical cyclone, they are found within the eyewall at a distance defined as the radius of maximum wind, or RMW. Unlike gusts, the value of these winds are...
  
  
• mean radiant temperature
  Mean radiant temperature
  The Mean Radiant Temperature is a concept arising from the fact that the net exchange of radiant energy between two objects is approximately proportional to their temperature difference multiplied by their ability to emit and absorb heat . Mean radiant temperature is simply the area weighted mean...
  
   (MRT)
• Mediterranean climate
  Mediterranean climate
  A Mediterranean climate is the climate typical of most of the lands in the Mediterranean Basin, and is a particular variety of subtropical climate...
  
  
• medium earth orbit
  Medium Earth Orbit
  Medium Earth orbit , sometimes called intermediate circular orbit , is the region of space around the Earth above low Earth orbit and below geostationary orbit ....
  
   (MEO) (intermediate circular orbit) (ICO)
• megathermal
  Megathermal
  In climatology, the term megathermal is sometimes used as a synonym for "tropical."In order for a particular place to qualify as having a megathermal climate, every single month out of the year must have an average temperature of 18°C or above.Megathermal climates are sometimes split into two...
  
   (macrothermal)
• melting
  Melting
  Melting, or fusion, is a physical process that results in the phase change of a substance from a solid to a liquid. The internal energy of a substance is increased, typically by the application of heat or pressure, resulting in a rise of its temperature to the melting point, at which the rigid...
  
  
• mercury (element)
  Mercury (element)
  Mercury is a chemical element with the symbol Hg and atomic number 80. It is also known as quicksilver or hydrargyrum...
  
   (see "Clean Air Act" in paragraph 3 under Release of mercury into the environment)
• mercury-in-glass thermometer
  Mercury-in-glass thermometer
  A mercury-in-glass thermometer, also known as a mercury thermometer, was invented by German physicist Daniel Gabriel Fahrenheit in 1724 and is a thermometer consisting of mercury in a glass tube. Calibrated marks on the tube allow the temperature to be read by the length of the mercury within the...
  
  
• mesosphere
  Mesosphere
  The mesosphere is the layer of the Earth's atmosphere that is directly above the stratosphere and directly below the thermosphere. In the mesosphere temperature decreases with increasing height. The upper boundary of the mesosphere is the mesopause, which can be the coldest naturally occurring...
  
  
• mesothermal
  Mesothermal
  In climatology, the term mesothermal is used to refer to certain forms of climate found typically in the Earth's Temperate Zones. It has a moderate amount of heat, with winters not cold enough to sustain snow cover...
  
   (in climatology)
• Met Office
  Met Office
  The Met Office , is the United Kingdom's national weather service, and a trading fund of the Department for Business, Innovation and Skills...
  
   (previously Meteorological Office) (the UK's national weather service)
• meteorological history of Hurricane Katrina
  Meteorological history of Hurricane Katrina
  The meteorological history of Hurricane Katrina, an extremely destructive Category 5 hurricane, began on August 23, 2005 when it originated as Tropical Depression Twelve near the Bahamas. The next day, the tropical depression strengthened to a tropical storm, and was named Katrina; it proceeded to...
  
  
• Meteorological Service of Canada
  Meteorological Service of Canada
  The Meteorological Service of Canada , also known as "The Canadian Weather Service", is a division of Environment Canada, which primarily provides public meteorological information and weather forecasts and warnings of severe weather and other environmental hazards...
  
   (MSC)
• meteorology
  Meteorology
  Meteorology is the interdisciplinary scientific study of the atmosphere. Studies in the field stretch back millennia, though significant progress in meteorology did not occur until the 18th century. The 19th century saw breakthroughs occur after observing networks developed across several countries...
  
  
• metrology
  Metrology
  Metrology is the science of measurement. Metrology includes all theoretical and practical aspects of measurement. The word comes from Greek μέτρον , "measure" + "λόγος" , amongst others meaning "speech, oration, discourse, quote, study, calculation, reason"...
  
  
• Miami Tornado (of May 12, 1997)
• Miami tornadoes of 2003
• microclimate
  Microclimate
  A microclimate is a local atmospheric zone where the climate differs from the surrounding area. The term may refer to areas as small as a few square feet or as large as many square miles...
  
  
• Mid-Atlantic United States flood of 2006
  Mid-Atlantic United States flood of 2006
  The Mid-Atlantic United States flood of 2006 was a significant flood that affected much of the Mid-Atlantic region of the eastern United States. The flooding was very widespread, affecting numerous rivers, lakes and communities from upstate New York to North Carolina. It is widely considered to be...
  
  
• middle latitudes
  Middle latitudes
  The middle latitudes are between 23°26'22" North and 66°33'39" North, and between 23°26'22" South and 66°33'39" South latitude, or, the Earth's temperate zones between the tropics and the Arctic and Antarctic. The prevailing winds in the middle latitudes are often very strong...
  
  
• midnight
  Midnight
  Midnight is the transition time period from one day to the next: the moment when the date changes. In the Roman time system, midnight was halfway between sunset and sunrise, varying according to the seasons....
  
  
• millimeter cloud radar
  Millimeter cloud radar
  Millimeter-wave cloud radar is a radar system designed to monitor cloud structure with wavelengths about ten times shorter than those used in conventional storm surveillance radars such as NEXRAD....
  
   (millimeter wave cloud radar) (MMCR)
• mist
  Mist
  Mist is a phenomenon of small droplets suspended in air. It can occur as part of natural weather or volcanic activity, and is common in cold air above warmer water, in exhaled air in the cold, and in a steam room of a sauna. It can also be created artificially with aerosol canisters if the...
  
  
• moisture
  Moisture
  Humidity is the amount of moisture the air can hold before it rains. Moisture refers to the presence of a liquid, especially water, often in trace amounts...
  
  
• moonlight
  Moonlight
  Moonlight is the light that reaches Earth from the Moon. This light does not originate from the Moon, but from sunlight. The Moon does not, however, reflect sunlight like a mirror, but it reflects light from those portions of its surface which the Sun's light strikes. See diffuse reflection.In...
  
  

N

• NASA Clean Air Study
  NASA Clean Air Study
  The NASA Clean Air Study has been led by the NASA in association with the Associated Landscape Contractors of America . Its results suggest that certain common indoor plants may provide a natural way of removing toxic agents such as benzene, formaldehyde and trichloroethylene from the air, helping...
  
  
• NASA Earth Observatory
  NASA Earth Observatory
  NASA Earth Observatory is an online publishing outlet for NASA which was created in 1999. It is the principal source of satellite imagery and other scientific information pertaining to the climate and the environment which are being provided by NASA for consumption by the general public...
  
  
• NASA World Wind
  NASA World Wind
  World Wind is an open-source virtual globe developed by NASA and the open source community for use on personal computers. Old versions need Microsoft Windows but the more recent Java version, , is cross platform and provides a suite of . The World Wind Java version was awarded in November 2009...
  
   (virtual globe)
• National Ambient Air Quality Standards
  National Ambient Air Quality Standards
  The National Ambient Air Quality Standards are standards established by the United States Environmental Protection Agency under authority of the Clean Air Act that apply for outdoor air throughout the country...
  
   (NAAQS) (in the US)
• National Center for Atmospheric Research
  National Center for Atmospheric Research
  The National Center for Atmospheric Research has multiple facilities, including the I. M. Pei-designed Mesa Laboratory headquarters in Boulder, Colorado. NCAR is managed by the nonprofit University Corporation for Atmospheric Research and sponsored by the National Science Foundation...
  
   (NCAR) (in the US)
• National Climatic Data Center
  National Climatic Data Center
  The United States National Climatic Data Center in Asheville, North Carolina is the world's largest active archive of weather data. The center became established in late 1951, with the move into the new facility occurring in early 1952....
  
   (NCDC) (in the US)
• National Emissions Standards for Hazardous Air Pollutants
  National Emissions Standards for Hazardous Air Pollutants
  The National Emissions Standards for Hazardous Air Pollutants are emissions standards set by the United States EPA for an air pollutant not covered by NAAQS that may cause an increase in fatalities or in serious, irreversible, or incapacitating illness...
  
   (NESHAPS) (in the US)
• (National Environmental Satellite, Data and Information Service: see) National Oceanic and Atmospheric Administration
  National Oceanic and Atmospheric Administration
  The National Oceanic and Atmospheric Administration , pronounced , like "noah", is a scientific agency within the United States Department of Commerce focused on the conditions of the oceans and the atmosphere...
  
   (NOAA) (in the US)
• National Geomagnetism Program
  National Geomagnetism Program
  The National Geomagnetism Program is a program directed by the USGS that monitors the Earth's magnetic field....
  
   (in the US)
• National Hurricane Center
  National Hurricane Center
  The National Hurricane Center , located at Florida International University in Miami, Florida, is the division of the National Weather Service responsible for tracking and predicting weather systems within the tropics between the Prime Meridian and the 140th meridian west poleward to the 30th...
  
   (in the US)
• National Map
  National Map
  The National Map is a collaborative effort of the United States Geological Survey and other federal, state, and local agencies to improve and deliver topographic information for the United States...
  
   (in the US)
• National Oceanic and Atmospheric Administration
  National Oceanic and Atmospheric Administration
  The National Oceanic and Atmospheric Administration , pronounced , like "noah", is a scientific agency within the United States Department of Commerce focused on the conditions of the oceans and the atmosphere...
  
   (NOAA) (in the US)
• (National Severe Storms Forecast Center [NSSFC]: renamed) Storm Prediction Center
  Storm Prediction Center
  The Storm Prediction Center , located in Norman, Oklahoma, is tasked with forecasting the risk of severe thunderstorms and tornadoes in the contiguous United States. The agency issues convective outlooks, mesoscale discussions, and watches as a part of this process...
  
   (SPC) (in the US)
• National Severe Storms Laboratory
  National Severe Storms Laboratory
  The National Severe Storms Laboratory is a National Oceanic and Atmospheric Administration weather research laboratory located at the National Weather Center in Norman, Oklahoma....
  
   (NSSL) (in the US)
• National Snow and Ice Data Center
  National Snow and Ice Data Center
  The National Snow and Ice Data Center, or NSIDC, is a United States information and referral center in support of polar and cryospheric research...
  
   (NSIDC) (in the US)
• National Solar Observatory
  National Solar Observatory
  The mission of the National Solar Observatory is to advance knowledge of the Sun, both as an astronomical object and as the dominant external influence on Earth, by providing forefront observational opportunities to the research community...
  
   (in the US)
• National Weather Center
  National Weather Center
  The National Weather Center , located on the campus of the University of Oklahoma, is a confederation of federal, state, and academic organizations that work together in partnership to improve understanding of events occurring in Earth's atmosphere over a wide range of time and space scales...
  
   (in the US)
• National Weather Service bulletin for New Orleans region
  National Weather Service bulletin for New Orleans region
  The National Weather Service bulletin for the New Orleans region of 10:11 a.m., August 28, 2005 was a vividly worded release issued by the local Weather Forecast Office in Slidell, Louisiana, warning of the devastation that the Gulf Coast of the United States could experience as a result of...
  
   (at 10:11 a.m., August 28, 2005)
• National Weather Service
  National Weather Service
  The National Weather Service , once known as the Weather Bureau, is one of the six scientific agencies that make up the National Oceanic and Atmospheric Administration of the United States government...
  
  
• nautical almanac
  Nautical almanac
  A nautical almanac is a publication describing the positions of a selection of celestial bodies for the purpose of enabling navigators to use celestial navigation to determine the position of their ship while at sea...
  
  
• nephology
  Nephology
  Nephology is the study of clouds and cloud formation. British meteorologist Luke Howard was a major researcher within this field, establishing a cloud classification system....
  
  
• nephoscope
  Nephoscope
  Nephoscope is an instrument for measuring the altitude, direction, and velocity of clouds.There are several types of nephoscopes:*the comb nephoscope developed by Besson;*the mirror nephoscope developed by Finemann;...
  
  
• night sky
  Night sky
  The term night sky refers to the sky as seen at night. The term is usually associated with astronomy, with reference to views of celestial bodies such as stars, the Moon, and planets that become visible on a clear night after the Sun has set. Natural light sources in a night sky include moonlight,...
  
  
• nimbus cloud
  Nimbus cloud
  A nimbus cloud is a cloud that produces precipitation. Usually the precipitation reaches the ground as rain, hail, snow, or sleet. Falling precipitation may evaporate as virga. Nimbus is a Latin word meaning in cloud or rain storm...
  
  
• nitrogen cycle
  Nitrogen cycle
  The nitrogen cycle is the process by which nitrogen is converted between its various chemical forms. This transformation can be carried out by both biological and non-biological processes. Important processes in the nitrogen cycle include fixation, mineralization, nitrification, and denitrification...
  
  
• (nitrogen pollution: see) eutrophication
  Eutrophication
  Eutrophication or more precisely hypertrophication, is the movement of a body of water′s trophic status in the direction of increasing plant biomass, by the addition of artificial or natural substances, such as nitrates and phosphates, through fertilizers or sewage, to an aquatic system...
  
   (see under Atmospheric deposition)
• nitrogenomics
• NOAA Weather Radio All Hazards
  NOAA Weather Radio All Hazards
  NOAA Weather Radio All Hazards is a network of radio stations broadcasting continuous weather information directly from a nearby National Weather Service office. It is operated by the NWS, an agency of the National Oceanic and Atmospheric Administration within the United States Department of...
  
   (of the US)
• noctilucent cloud
  Noctilucent cloud
  Night clouds or Noctilucent clouds are tenuous cloud-like phenomena that are the "ragged-edge" of a much brighter and pervasive polar cloud layer called polar mesospheric clouds in the upper atmosphere, visible in a deep twilight. They are made of crystals of water ice. The name means roughly night...
  
  
• North Atlantic tropical cyclone
• North Pole
  North Pole
  The North Pole, also known as the Geographic North Pole or Terrestrial North Pole, is, subject to the caveats explained below, defined as the point in the northern hemisphere where the Earth's axis of rotation meets its surface...
  
  
• numerical weather prediction
  Numerical weather prediction
  Numerical weather prediction uses mathematical models of the atmosphere and oceans to predict the weather based on current weather conditions. Though first attempted in the 1920s, it was not until the advent of computer simulation in the 1950s that numerical weather predictions produced realistic...
  
  

O

• observational astronomy
  Observational astronomy
  Observational astronomy is a division of the astronomical science that is concerned with getting data, in contrast with theoretical astrophysics which is mainly concerned with finding out the measurable implications of physical models...
  
   (see "light pollution" in places)
• observatory
  Observatory
  An observatory is a location used for observing terrestrial or celestial events. Astronomy, climatology/meteorology, geology, oceanography and volcanology are examples of disciplines for which observatories have been constructed...
  
   (see also list of observatories)
• occultation
  Occultation
  An occultation is an event that occurs when one object is hidden by another object that passes between it and the observer. The word is used in astronomy . It can also refer to any situation wherein an object in the foreground blocks from view an object in the background...
  
  
• oceanic climate
  Oceanic climate
  An oceanic climate, also called marine west coast climate, maritime climate, Cascadian climate and British climate for Köppen climate classification Cfb and subtropical highland for Köppen Cfb or Cwb, is a type of climate typically found along the west coasts at the middle latitudes of some of the...
  
  
• Office of Oceanic and Atmospheric Research
  Office of Oceanic and Atmospheric Research
  The Office of Oceanic and Atmospheric Research is a division of the National Oceanic and Atmospheric Administration . OAR is also referred to as NOAA Research....
  
   (OAR)
• 1999 Oklahoma tornado outbreak
• orographic lift
  Orographic lift
  Orographic lift occurs when an air mass is forced from a low elevation to a higher elevation as it moves over rising terrain. As the air mass gains altitude it quickly cools down adiabatically, which can raise the relative humidity to 100% and create clouds and, under the right conditions,...
  
  
• oxygen
  Oxygen
  Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
  
  
• oxygen cycle
  Oxygen cycle
  The Oxygen cycle is the biogeochemical cycle that describes the movement of oxygen within its three main reservoirs: the atmosphere , the total content of biological matter within the biosphere , and the lithosphere...
  
  
• ozone
  Ozone
  Ozone , or trioxygen, is a triatomic molecule, consisting of three oxygen atoms. It is an allotrope of oxygen that is much less stable than the diatomic allotrope...
  
  
• ozone depletion
  Ozone depletion
  Ozone depletion describes two distinct but related phenomena observed since the late 1970s: a steady decline of about 4% per decade in the total volume of ozone in Earth's stratosphere , and a much larger springtime decrease in stratospheric ozone over Earth's polar regions. The latter phenomenon...
  
  
• ozone depletion potential
  Ozone depletion potential
  The ozone depletion potential of a chemical compound is the relative amount of degradation to the ozone layer it can cause, with trichlorofluoromethane being fixed at an ODP of 1.0. Chlorodifluoromethane , for example, has an ODP of 0.055...
  
   (ODP)
• ozone layer
  Ozone layer
  The ozone layer is a layer in Earth's atmosphere which contains relatively high concentrations of ozone . This layer absorbs 97–99% of the Sun's high frequency ultraviolet light, which is potentially damaging to the life forms on Earth...
  
   (ozonosphere layer)
• ozone-oxygen cycle
  Ozone-oxygen cycle
  The ozone-oxygen cycle is the process by which ozone is continually regenerated in Earth's stratosphere, all the while converting ultraviolet radiation into heat. In 1930 Sydney Chapman resolved the chemistry involved. The process is commonly called the Chapman cycle by atmospheric scientists.Most...
  
  

P

• Pacific decadal oscillation
  Pacific decadal oscillation
  The Pacific Decadal Oscillation is a pattern of Pacific climate variability that shifts phases on at least inter-decadal time scale, usually about 20 to 30 years. The PDO is detected as warm or cool surface waters in the Pacific Ocean, north of 20° N...
  
  
• paleoclimatology
  Paleoclimatology
  Paleoclimatology is the study of changes in climate taken on the scale of the entire history of Earth. It uses a variety of proxy methods from the Earth and life sciences to obtain data previously preserved within rocks, sediments, ice sheets, tree rings, corals, shells and microfossils; it then...
  
  
• paleomagnetism
  Paleomagnetism
  Paleomagnetism is the study of the record of the Earth's magnetic field in rocks. Certain minerals in rocks lock-in a record of the direction and intensity of the magnetic field when they form. This record provides information on the past behavior of Earth's magnetic field and the past location of...
  
  
• paleotempestology
  Paleotempestology
  Paleotempestology is the study of past tropical cyclone activity by means of geological proxies as well as historical documentary records. The term was coined by Kerry Emanuel.-Sedimentary proxy records:...
  
  
• parts-per notation
  Parts-per notation
  In science and engineering, the parts-per notation is a set of pseudo units to describe small values of miscellaneous dimensionless quantities, e.g. mole fraction or mass fraction. Since these fractions are quantity-per-quantity measures, they are pure numbers with no associated units of measurement...
  
  
• photovore
• planetary boundary layer
  Planetary boundary layer
  The planetary boundary layer , also known as the atmospheric boundary layer , is the lowest part of the atmosphere and its behavior is directly influenced by its contact with a planetary surface. On Earth it usually responds to changes in surface forcing in an hour or less...
  
   (PBL)
• pluvial lake
  Pluvial lake
  A pluvial lake is a landlocked basin which fills with rainwater during times of glaciation, when precipitation is higher. Pluvial lakes that have since evaporated and dried out may also be referred to as paleolakes.-Geology:...
  
  
• polar circle
  Polar circle
  A polar circle is either the Arctic Circle or the Antarctic Circle. On Earth, the Arctic Circle is located at a latitude of  N, and the Antarctic Circle is located at a latitude of  S....
  
  
• polar climate
  Polar climate
  Regions with a polar climate are characterized by a lack of warm summers . Regions with polar climate cover over 20% of the Earth. The sun shines 24 hours in the summer, and barely ever shines at all in the winter...
  
  
• polar easterlies
  Polar easterlies
  The polar easterlies are the dry, cold prevailing winds that blow from the high-pressure areas of the polar highs at the north and south poles towards low-pressure areas within the Westerlies at high latitudes...
  
  
• polar high
  Polar high
  The polar highs are areas of high atmospheric pressure around the north and south poles, south polar high being the stronger one because land gains and loses heat more effectively than sea...
  
  
• polar ice cap
  Polar ice cap
  A polar ice cap is a high latitude region of a planet or natural satellite that is covered in ice. There are no requirements with respect to size or composition for a body of ice to be termed a polar ice cap, nor any geological requirement for it to be over land; only that it must be a body of...
  
  
• (polar light: see) aurora (astronomy)
  Aurora (astronomy)
  An aurora is a natural light display in the sky particularly in the high latitude regions, caused by the collision of energetic charged particles with atoms in the high altitude atmosphere...
  
  
• polar low
  Polar low
  A polar low is a small-scale, long-lived atmospheric low pressure system that is found over the ocean areas poleward of the main polar front in both the Northern and Southern Hemispheres. The systems usually have a horizontal length scale of less than and exist for no more than a couple of days. ...
  
  
• (polar mesospheric cloud) noctilucent cloud
  Noctilucent cloud
  Night clouds or Noctilucent clouds are tenuous cloud-like phenomena that are the "ragged-edge" of a much brighter and pervasive polar cloud layer called polar mesospheric clouds in the upper atmosphere, visible in a deep twilight. They are made of crystals of water ice. The name means roughly night...
  
  
• polar mesospheric summer echoes
  Polar mesospheric summer echoes
  Polar mesospheric summer echoes is the phenomenon of anomalous radar echoes found between 80-90 km in altitude from May through early August in the Arctic, and from November through to February in the Antarctic. These strong radar echoes are associated with the extremely cold temperatures that...
  
   (PMSE)
• polar night
  Polar night
  The polar night occurs when the night lasts for more than 24 hours. This occurs only inside the polar circles. The opposite phenomenon, the polar day, or midnight sun, occurs when the sun stays above the horizon for more than 24 hours.-Description:...
  
  
• polar region
  Polar region
  Earth's polar regions are the areas of the globe surrounding the poles also known as frigid zones. The North Pole and South Pole being the centers, these regions are dominated by the polar ice caps, resting respectively on the Arctic Ocean and the continent of Antarctica...
  
  
• (polar reversal) magnetic polarity reversal
• polar stratospheric cloud
  Polar stratospheric cloud
  Polar stratospheric clouds or PSCs, also known as nacreous clouds , are clouds in the winter polar stratosphere at altitudes of 15,000–25,000 meters...
  
   (PSC) (nacreous cloud)
• Polarization (waves) (see under Polarization effects in everyday life)
• pole shift theory
  Pole shift theory
  The cataclysmic pole shift hypothesis suggests that there have been geologically rapid shifts in the relative positions of the modern-day geographic locations of the poles and the axis of rotation of the Earth, creating calamities such as floods and tectonic events.No form of the hypothesis is...
  
  
• positive streamer
• post-glacial rebound
  Post-glacial rebound
  Post-glacial rebound is the rise of land masses that were depressed by the huge weight of ice sheets during the last glacial period, through a process known as isostasy...
  
  
• potential evaporation
  Potential evaporation
  Potential evaporation or potential evapotranspiration is defined as the amount of evaporation that would occur if a sufficient water source were available. If the actual evapotranspiration is considered the net result of atmospheric demand for moisture from a surface and the ability of the...
  
  
• potential temperature
• pyrocumulus

R

• radiance
  Radiance
  Radiance and spectral radiance are radiometric measures that describe the amount of radiation such as light or radiant heat that passes through or is emitted from a particular area, and falls within a given solid angle in a specified direction. They are used to characterize both emission from...
  
  
• radiant barrier
  Radiant barrier
  Radiant barriers or reflective barriers inhibit heat transfer by thermal radiation. Thermal energy may also be transferred via conduction or convection, however, and radiant barriers do not necessarily protect against heat transfer via conduction or convection....
  
  
• radiant energy
  Radiant energy
  Radiant energy is the energy of electromagnetic waves. The quantity of radiant energy may be calculated by integrating radiant flux with respect to time and, like all forms of energy, its SI unit is the joule. The term is used particularly when radiation is emitted by a source into the...
  
  
• radiation
  Radiation
  In physics, radiation is a process in which energetic particles or energetic waves travel through a medium or space. There are two distinct types of radiation; ionizing and non-ionizing...
  
  
• radiation budget
• radiation hormesis
  Radiation hormesis
  Radiation hormesis is the hypothesis that low doses of ionizing radiation are beneficial, stimulating the activation of repair mechanisms that protect against disease, that are not activated in absence of ionizing radiation...
  
  
• radiation poisoning
  Radiation poisoning
  Acute radiation syndrome also known as radiation poisoning, radiation sickness or radiation toxicity, is a constellation of health effects which occur within several months of exposure to high amounts of ionizing radiation...
  
   (radiation sickness)
• radiative cooling
  Radiative cooling
  Radiative cooling is the process by which a body loses heat by thermal radiation.- Earth's energy budget :In the case of the earth-atmosphere system it refers to the process by which long-wave radiation is emitted to balance the absorption of short-wave energy from the sun.The exact process by...
  
  
• radiative forcing
  Radiative forcing
  In climate science, radiative forcing is generally defined as the change in net irradiance between different layers of the atmosphere. Typically, radiative forcing is quantified at the tropopause in units of watts per square meter. A positive forcing tends to warm the system, while a negative...
  
  
• radiological weapon
  Radiological weapon
  A radiological weapon or radiological dispersion device is any weapon that is designed to spread radioactive material with the intent to kill, and cause disruption upon a city or nation....
  
   (radiological dispersion device [RDD])
• radiosonde
  Radiosonde
  A radiosonde is a unit for use in weather balloons that measures various atmospheric parameters and transmits them to a fixed receiver. Radiosondes may operate at a radio frequency of 403 MHz or 1680 MHz and both types may be adjusted slightly higher or lower as required...
  
  
• radius of outermost closed isobar
  Radius of outermost closed isobar
  style="float: right; clear: right; background-color: transparent; margin-left: 0em"|The radius of outermost closed isobar is one of the quantities used to determine the size of a tropical cyclone. It is determined by measuring the radii from the center of the storm to its outermost closed isobar...
  
  
• rain
  Rain
  Rain is liquid precipitation, as opposed to non-liquid kinds of precipitation such as snow, hail and sleet. Rain requires the presence of a thick layer of the atmosphere to have temperatures above the melting point of water near and above the Earth's surface...
  
  
• rain fade
  Rain fade
  Rain fade refers primarily to the absorption of a microwave radio frequency signal by atmospheric rain, snow or ice, and losses are especially prevalent at frequencies above 11 GHz. It also refers to the degradation of a signal caused by the electromagnetic interference of the leading edge of a...
  
   (fading of signal by rain or snow)
• rain gauge
  Rain gauge
  A rain gauge is a type of instrument used by meteorologists and hydrologists to gather and measure the amount of liquid precipitation over a set period of time....
  
  
• rain sensor
  Rain sensor
  A rain sensor or rain switch is a switching device actuated by rainfall. There are two main applications for rain sensors. The first is a water conservation device connected to an automatic irrigation system that causes the system to shut down in the event of rainfall...
  
  
• rain shadow
  Rain shadow
  A rain shadow is a dry area on the lee side of a mountainous area. The mountains block the passage of rain-producing weather systems, casting a "shadow" of dryness behind them. As shown by the diagram to the right, the warm moist air is "pulled" by the prevailing winds over a mountain...
  
  
• rainbow
  Rainbow
  A rainbow is an optical and meteorological phenomenon that causes a spectrum of light to appear in the sky when the Sun shines on to droplets of moisture in the Earth's atmosphere. It takes the form of a multicoloured arc...
  
  
• rainforest
  Rainforest
  Rainforests are forests characterized by high rainfall, with definitions based on a minimum normal annual rainfall of 1750-2000 mm...
  
  
• rarefaction
  Rarefaction
  Rarefaction is the reduction of a medium's density, or the opposite of compression.A natural example of this is as a phase in a sound wave or phonon. Half of a sound wave is made up of the compression of the medium, and the other half is the decompression or rarefaction of the medium.Another...
  
  
• RealClimate
  RealClimate
  RealClimate is a commentary site on climatology. The site's contributors are a group of climate scientists whose goal is to provide a quick response to developing stories and providing the context sometimes missing in mainstream commentary. The discussion is intended to be restricted to scientific...
  
   (commentary site on climate science)
• RealSky
  RealSky
  RealSky is the name of a commercially available, digital photographic sky atlas. It is a subset of the Digitized Sky Survey and was published in 1996 by the Astronomical Society of the Pacific....
  
   (digital photographic sky atlas)
• relative humidity
  Relative humidity
  Relative humidity is a term used to describe the amount of water vapor in a mixture of air and water vapor. It is defined as the partial pressure of water vapor in the air-water mixture, given as a percentage of the saturated vapor pressure under those conditions...
  
  
• relative pressure
• (relief precipitation: see) orographic lift
  Orographic lift
  Orographic lift occurs when an air mass is forced from a low elevation to a higher elevation as it moves over rising terrain. As the air mass gains altitude it quickly cools down adiabatically, which can raise the relative humidity to 100% and create clouds and, under the right conditions,...
  
  
• research balloon
  Research balloon
  Research balloons are balloons that are used for scientific research. They are usually unmanned, filled with a lighter-than-air gas like helium, and fly at high altitudes....
  
  
• resistance thermometer
  Resistance thermometer
  Resistance thermometers, also called resistance temperature detectors or resistive thermal devices , are sensors used to measure temperature by correlating the resistance of the RTD element with temperature. Most RTD elements consist of a length of fine coiled wire wrapped around a ceramic or glass...
  
   (resistance temperature detector) (RTD)
• rime (frost)
  Rime (frost)
  Hard rime is a white ice that forms when the water droplets in fog freeze to the outer surfaces of objects. It is often seen on trees atop mountains and ridges in winter, when low-hanging clouds cause freezing fog...
  
  

S

• Saffir-Simpson Hurricane Scale
  Saffir-Simpson Hurricane Scale
  The Saffir–Simpson Hurricane Scale , or the Saffir–Simpson Hurricane Wind Scale , classifies hurricanes — Western Hemisphere tropical cyclones that exceed the intensities of tropical depressions and tropical storms — into five categories distinguished by the intensities of their sustained winds...
  
  
• satellite temperature measurements
  Satellite temperature measurements
  The temperature of the atmosphere at various altitudes as well as sea and land surface temperatures can be inferred from satellite measurements. Weather satellites do not measure temperature directly but measure radiances in various wavelength bands...
  
  
• (Sea Islands Hurricane) 1893 Sea Islands Hurricane
  1893 Sea Islands Hurricane
  On August 27, 1893 a major hurricane which came to be known as the Sea Islands Hurricane struck the United States near Savannah, Georgia. It was one of two deadly hurricanes during the 1893 Atlantic hurricane season; the storm killed an estimated 1,000–2,000 people, mostly from storm surge...
  
  
• sea level
  Sea level
  Mean sea level is a measure of the average height of the ocean's surface ; used as a standard in reckoning land elevation...
  
  
• (sea level pressure) atmospheric pressure
  Atmospheric pressure
  Atmospheric pressure is the force per unit area exerted into a surface by the weight of air above that surface in the atmosphere of Earth . In most circumstances atmospheric pressure is closely approximated by the hydrostatic pressure caused by the weight of air above the measurement point...
  
  
• sea surface temperature
  Sea surface temperature
  Sea surface temperature is the water temperature close to the oceans surface. The exact meaning of surface varies according to the measurement method used, but it is between and below the sea surface. Air masses in the Earth's atmosphere are highly modified by sea surface temperatures within a...
  
   (SST)
• severe weather
  Severe weather
  Severe weather phenomena are weather conditions that are hazardous to human life and property.- Examples Include :Severe weather can occur under a variety of situations, but three characteristics are generally needed: a temperature or moisture boundary, moisture, and , instability in the...
  
  
• severe weather terminology (United States)
  Severe weather terminology (United States)
  This article describes the United States National Weather Service severe weather terminology. The NWS defines precise meanings for nearly all its weather terms. This article describes NWS terminology and related NWS weather scales...
  
  
• sky
  Sky
  The sky is the part of the atmosphere or outer space visible from the surface of any astronomical object. It is difficult to define precisely for several reasons. During daylight, the sky of Earth has the appearance of a pale blue surface because the air scatters the sunlight. The sky is sometimes...
  
  
• skyglow
  Skyglow
  Skyglow is the illumination of the night sky or parts of it. The most common cause of skyglow is artificial light that emits light pollution, which accumulates into a vast glow that can be seen from miles away and from high in the sky...
  
  
• smoke
  Smoke
  Smoke is a collection of airborne solid and liquid particulates and gases emitted when a material undergoes combustion or pyrolysis, together with the quantity of air that is entrained or otherwise mixed into the mass. It is commonly an unwanted by-product of fires , but may also be used for pest...
  
  
• snow
  Snow
  Snow is a form of precipitation within the Earth's atmosphere in the form of crystalline water ice, consisting of a multitude of snowflakes that fall from clouds. Since snow is composed of small ice particles, it is a granular material. It has an open and therefore soft structure, unless packed by...
  
  
• Solar and Heliospheric Observatory
  Solar and Heliospheric Observatory
  The Solar and Heliospheric Observatory is a spacecraft built by a European industrial consortium led by Matra Marconi Space that was launched on a Lockheed Martin Atlas IIAS launch vehicle on December 2, 1995 to study the Sun, and has discovered over 2100 comets. It began normal operations in May...
  
  
• solar azimuth angle
  Solar azimuth angle
  The solar azimuth angle is the azimuth angle of the sun. It is most often defined as the angle from due north in a clockwise direction.It can be calculated in various way. In different times, it has been explained in different ways. It can be calculated, to a good approximation, using the following...
  
  
• solar cell
  Solar cell
  A solar cell is a solid state electrical device that converts the energy of light directly into electricity by the photovoltaic effect....
  
  
• solar collector
  Solar collector
  -See also:*Solar thermal collector*Solar water heating*Solar air heating*Photovoltaic module*Renewable heat*Concentrating solar power...
  
  
• solar constant
  Solar constant
  The solar constant, a measure of flux density, is the amount of incoming solar electromagnetic radiation per unit area that would be incident on a plane perpendicular to the rays, at a distance of one astronomical unit...
  
  
• solar cycle
  Solar cycle
  The solar cycle, or the solar magnetic activity cycle, is a periodic change in the amount of irradiation from the Sun that is experienced on Earth. It has a period of about 11 years, and is one component of solar variation, the other being aperiodic fluctuations. Solar variation causes changes in...
  
  
• solar eclipse
  Solar eclipse
  As seen from the Earth, a solar eclipse occurs when the Moon passes between the Sun and the Earth, and the Moon fully or partially blocks the Sun as viewed from a location on Earth. This can happen only during a new moon, when the Sun and the Moon are in conjunction as seen from Earth. At least...
  
  
• solar flare
  Solar flare
  A solar flare is a sudden brightening observed over the Sun surface or the solar limb, which is interpreted as a large energy release of up to 6 × 1025 joules of energy . The flare ejects clouds of electrons, ions, and atoms through the corona into space. These clouds typically reach Earth a day...
  
   (see under Hazards)
• solar furnace
  Solar furnace
  A solar furnace is a structure that captures sunlight to produce high temperatures, usually for industry. This is done with a curved mirror that acts as a parabolic reflector, concentrating light onto a focal point...
  
  
• solar greenhouse (technical)
• solar heating
• solar maximum
  Solar maximum
  Solar maximum or solar max is the period of greatest solar activity in the solar cycle of the sun. During solar maximum, sunspots appear....
  
  
• Solar Maximum Mission
  Solar Maximum Mission
  The Solar Maximum Mission satellite was designed to investigate solar phenomenon, particularly solar flares. It was launched on February 14, 1980....
  
  
• solar minimum
  Solar minimum
  Solar minimum is the period of least solar activity in the solar cycle of the sun. During this time, sunspot and solar flare activity diminishes, and often does not occur for days at a time...
  
  
• solar mirror
  Solar mirror
  A solar mirror is a reflective surface used for gathering and reflecting solar energy in a system being powered by solar energy. It comprises a substrate with a reflective layer for reflecting the solar energy, and in most cases an interference layer...
  
  
• solar proton event
  Solar proton event
  A Solar proton event occurs when protons emitted by the Sun become accelerated to very high energies either close to the Sun during a solar flare or in interplanetary space by the shocks associated with coronal mass ejections. These high energy protons cause several effects. They can penetrate the...
  
  
• solar radiation (solar irradiance)
• (solar storm) geomagnetic storm
  Geomagnetic storm
  A geomagnetic storm is a temporary disturbance of the Earth's magnetosphere caused by a disturbance in the interplanetary medium. A geomagnetic storm is a major component of space weather and provides the input for many other components of space weather...
  
  
• solar thermal collector
  Solar thermal collector
  A solar thermal collector is a solar collector designed to collect heat by absorbing sunlight. The term is applied to solar hot water panels, but may also be used to denote more complex installations such as solar parabolic, solar trough and solar towers or simpler installations such as solar air...
  
  
• solar thermal energy
  Solar thermal energy
  Solar thermal energy is a technology for harnessing solar energy for thermal energy . Solar thermal collectors are classified by the United States Energy Information Administration as low-, medium-, or high-temperature collectors. Low-temperature collectors are flat plates generally used to heat...
  
  
• solar updraft tower
  Solar updraft tower
  The solar updraft tower is a renewable-energy power plant. It combines the chimney effect, the greenhouse effect and the wind turbine. Air is heated by sunshine and contained in a very large greenhouse-like structure around the base of a tall chimney, and the resulting convection causes air to...
  
  
• solar variation
  Solar variation
  Solar variation is the change in the amount of radiation emitted by the Sun and in its spectral distribution over years to millennia. These variations have periodic components, the main one being the approximately 11-year solar cycle . The changes also have aperiodic fluctuations...
  
  
• solar wind
  Solar wind
  The solar wind is a stream of charged particles ejected from the upper atmosphere of the Sun. It mostly consists of electrons and protons with energies usually between 1.5 and 10 keV. The stream of particles varies in temperature and speed over time...
  
  
• solarium

• space weather
  Space weather
  Space weather is the concept of changing environmental conditions in near-Earth space or thespace from the Sun's atmosphere to the Earth's atmosphere. It is distinct from the concept ofweather within the Earth's planetary atmosphere...
  
  
• (specific humidity: see) humidity
  Humidity
  Humidity is a term for the amount of water vapor in the air, and can refer to any one of several measurements of humidity. Formally, humid air is not "moist air" but a mixture of water vapor and other constituents of air, and humidity is defined in terms of the water content of this mixture,...
  
   (see under Specific Humidity)
• (standard atmospheric pressure) atmospheric pressure
  Atmospheric pressure
  Atmospheric pressure is the force per unit area exerted into a surface by the weight of air above that surface in the atmosphere of Earth . In most circumstances atmospheric pressure is closely approximated by the hydrostatic pressure caused by the weight of air above the measurement point...
  
   (standard atmosphere)
• standard conditions for temperature and pressure
  Standard conditions for temperature and pressure
  Standard condition for temperature and pressure are standard sets of conditions for experimental measurements established to allow comparisons to be made between different sets of data...
  
  
• storm
  Storm
  A storm is any disturbed state of an astronomical body's atmosphere, especially affecting its surface, and strongly implying severe weather...
  
  
• storm cellar
  Storm cellar
  A storm shelter or storm cellar is a type of underground bunker designed to protect the occupants from violent severe weather, particularly tornadoes...
  
  
• storm chasing
  Storm chasing
  Storm chasing is broadly defined as the pursuit of any severe weather condition, regardless of motive, which can be curiosity, adventure, scientific exploration or for news professions/media coverage....
  
  
• storm drain
  Storm drain
  A storm drain, storm sewer , stormwater drain or drainage well system or simply a drain or drain system is designed to drain excess rain and ground water from paved streets, parking lots, sidewalks, and roofs. Storm drains vary in design from small residential dry wells to large municipal systems...
  
   (storm sewer) (stormwater drain)
• storm surge
  Storm surge
  A storm surge is an offshore rise of water associated with a low pressure weather system, typically tropical cyclones and strong extratropical cyclones. Storm surges are caused primarily by high winds pushing on the ocean's surface. The wind causes the water to pile up higher than the ordinary sea...
  
  
• storm tide
  Storm tide
  A storm tide is a tide with a high flood period caused by a storm. Storm tides can be a severe danger to the coast and the people living along the coast. The water level can rise to more than 5 meters above the normal tide....
  
  
• storm track
  Storm track
  Storm tracks are the relatively narrow zones in the Atlantic and Pacific along which most Atlantic or Pacific extratropical cyclones travel.The storm tracks begin in the westernmost parts of Atlantic and Pacific, where the large temperature contrasts between land and sea cause cyclones to form,...
  
  
• storm warning
  Storm warning
  At sea, a storm warning is a warning issued by the National Weather Service of the United States when winds between 48 knots and 63 knots are occurring or predicted to occur soon. The winds must not be associated with a tropical cyclone...
  
   (see same for "storm watch")
• storm-scale
  Storm-scale
  Storm-scale is a scale of sizes of weather systems on the order of individual thunderstorms.-See also:* Synoptic scale meteorology* Mesoscale meteorology* Microscale meteorology* Misoscale meteorology...
  
  
• stormwater
  Stormwater
  Stormwater is water that originates during precipitation events. It may also be used to apply to water that originates with snowmelt that enters the stormwater system...
  
  
• stratopause
  Stratopause
  The stratopause is the level of the atmosphere which is the boundary between two layers, stratosphere and the mesosphere...
  
  
• stratosphere
  Stratosphere
  The stratosphere is the second major layer of Earth's atmosphere, just above the troposphere, and below the mesosphere. It is stratified in temperature, with warmer layers higher up and cooler layers farther down. This is in contrast to the troposphere near the Earth's surface, which is cooler...
  
  
• subarctic
  Subarctic
  The Subarctic is a region in the Northern Hemisphere immediately south of the true Arctic and covering much of Alaska, Canada, the north of Scandinavia, Siberia, and northern Mongolia...
  
  
• subarctic climate
  Subarctic climate
  The subarctic climate is a climate characterized by long, usually very cold winters, and short, cool to mild summers. It is found on large landmasses, away from the moderating effects of an ocean, generally at latitudes from 50° to 70°N poleward of the humid continental climates...
  
  
• subtropical cyclone
  Subtropical cyclone
  A subtropical cyclone is a weather system that has some characteristics of a tropical and an extratropical cyclone. As early as the 1950s, meteorologists were unclear whether they should be characterized as tropical or extratropical cyclones. They were officially recognized by the National...
  
   (see same for "subtropical depression" and for "subtropical storm")
• subtropics
  Subtropics
  The subtropics are the geographical and climatical zone of the Earth immediately north and south of the tropical zone, which is bounded by the Tropic of Cancer and the Tropic of Capricorn, at latitudes 23.5°N and 23.5°S...
  
   (see same for "subtropical" and for "subtropical climate")
• sudden ionospheric disturbance
  Sudden Ionospheric Disturbance
  A sudden ionospheric disturbance is an abnormally high ionization/plasma density in the D region of the ionosphere caused by a solar flare...
  
   (SID)
• sudden stratospheric warming
  Sudden stratospheric warming
  A sudden stratospheric warming is an event where the polar vortex of westerly winds in the winter hemisphere abruptly slows down or even reverses direction, accompanied by a rise of stratospheric temperature by several tens of kelvins...
  
  
• sun
  Sun
  The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
  
  
• sun dog
  Sun dog
  A sun dog or sundog, scientific name parhelion ; , also called a mock sun or a phantom sun, is an atmospheric phenomenon that creates bright spots of light in the sky, often on a luminous ring or halo on either side of the sun.Sundogs may appear as a colored patch of light to the left or right of...
  
   (sundog) (parhelion)
• sunlight
  Sunlight
  Sunlight, in the broad sense, is the total frequency spectrum of electromagnetic radiation given off by the Sun. On Earth, sunlight is filtered through the Earth's atmosphere, and solar radiation is obvious as daylight when the Sun is above the horizon.When the direct solar radiation is not blocked...
  
  
• sunshower
  Sunshower
  A sunshower or sun shower is a meteorological phenomenon in which rain falls while the sun is shining. These conditions often lead to the appearance of a rainbow, if the sun is at a low enough angle. Although used in the United States, Canada, Australia, New Zealand, Ireland, and parts of Britain,...
  
  
• sunspot
  Sunspot
  Sunspots are temporary phenomena on the photosphere of the Sun that appear visibly as dark spots compared to surrounding regions. They are caused by intense magnetic activity, which inhibits convection by an effect comparable to the eddy current brake, forming areas of reduced surface temperature....
  
   (see under "Significant events")
• surface temperature inversion
• synoptic scale meteorology
  Synoptic scale meteorology
  The synoptic scale in meteorology is a horizontal length scale of the order of 1000 kilometres or more. This corresponds to a horizontal scale typical of mid-latitude depressions...
  
  

T

• temperature
  Temperature
  Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
  
  
• temperature extremes
• (temperature inversion) inversion (meteorology)
  Inversion (meteorology)
  In meteorology, an inversion is a deviation from the normal change of an atmospheric property with altitude. It almost always refers to a temperature inversion, i.e...
  
  
• temperature record
  Temperature record
  The temperature record shows the fluctuations of the temperature of the atmosphere and the oceans through various spans of time. The most detailed information exists since 1850, when methodical thermometer-based records began. There are numerous estimates of temperatures since the end of the...
  
  
• temperature record of the past 1000 years
  Temperature record of the past 1000 years
  The temperature record of the 2nd millennium describes the reconstruction of temperatures since 1000 CE on the Northern Hemisphere, later extended back to 1 CE and also to cover the southern hemisphere. A reconstruction is needed because a reliable surface temperature record exists only since about...
  
  
• The Weather Channel
  The Weather Channel
  The Weather Channel is a US cable and satellite television network since May 2, 1982, that broadcasts weather forecasts and weather-related news, along with entertainment programming related to weather 24 hours a day...
  
  
• The Weather Network
  The Weather Network
  The Weather Network is a Canadian English language Category A specialty channel that broadcasts weather-related news and information 24 hours a day....
  
  
• thermal equator
  Thermal equator
  The thermal equator is a belt encircling the Earth, defined by the set of locations having the highest mean annual temperature at each longitude around the globe...
  
  
• thermometer
  Thermometer
  Developed during the 16th and 17th centuries, a thermometer is a device that measures temperature or temperature gradient using a variety of different principles. A thermometer has two important elements: the temperature sensor Developed during the 16th and 17th centuries, a thermometer (from the...
  
  
• thunder
  Thunder
  Thunder is the sound made by lightning. Depending on the nature of the lightning and distance of the listener, thunder can range from a sharp, loud crack to a long, low rumble . The sudden increase in pressure and temperature from lightning produces rapid expansion of the air surrounding and within...
  
  
• thundersnow
  Thundersnow
  Thundersnow, also known as a winter thunderstorm or a thunder snowstorm, is a relatively rare kind of thunderstorm with snow falling as the primary precipitation instead of rain. It typically falls in regions of strong upward motion within the cold sector of an extratropical cyclone...
  
  
• thunderstorm
  Thunderstorm
  A thunderstorm, also known as an electrical storm, a lightning storm, thundershower or simply a storm is a form of weather characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere known as thunder. The meteorologically assigned cloud type associated with the...
  
   (electrical storm)
• TIMED
  TIMED
  The TIMED mission was a two year project to study the dynamics of the Mesosphere and Lower Thermosphere portion of the Earth's atmosphere. The mission was launched from Vandenberg Air Force Base in California on December 7, 2001 aboard a Delta II rocket launch vehicle...
  
   (Thermosphere Ionosphere Mesosphere Energetics and Dynamics)
• tor
• tornado
  Tornado
  A tornado is a violent, dangerous, rotating column of air that is in contact with both the surface of the earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. They are often referred to as a twister or a cyclone, although the word cyclone is used in meteorology in a wider...
  
  
• tornado warning
  Tornado warning
  A tornado warning is an alert issued by government weather services to warn that severe thunderstorms with tornadoes may be imminent. It can be issued after a tornado or funnel cloud has been spotted by eye, or more commonly if there are radar indications of tornado formation...
  
  
• tornado watch
  Tornado watch
  A tornado watch is issued when conditions are right for a tornado to form. Since any thunderstorm capable of producing a tornado is defined as severe, a tornado watch is also automatically a severe thunderstorm watch...
  
  
• tornadogenesis
  Tornadogenesis
  Tornadogenesis is the process by which a tornado forms. There are many types of tornadoes, and each type of tornado can have several different methods of formation. Scientific study is ongoing, as some aspects of tornado formation remain a mystery....
  
  
• torr
  Torr
  The torr is a non-SI unit of pressure with the ratio of 760 to 1 standard atmosphere, chosen to be roughly equal to the fluid pressure exerted by a millimetre of mercury, i.e., a pressure of 1 torr is approximately equal to 1 mmHg...
  
   (symbol: Torr) (millimetre of mercury) (mmHg)
• Total Ozone Mapping Spectrometer
  Total Ozone Mapping Spectrometer
  The Total Ozone Mapping Spectrometer is a satellite instrument for measuring ozone values. It has been flown on NASA-satellites. Of the five TOMS instruments which were built, four entered successful orbit...
  
   (TOMS)
• tropical climate
  Tropical climate
  A tropical climate is a climate of the tropics. In the Köppen climate classification it is a non-arid climate in which all twelve months have mean temperatures above...
  
  
• tropical cyclogenesis
  Tropical cyclogenesis
  Tropical cyclogenesis is the term that describes the development and strengthening of a tropical cyclone in the atmosphere. The mechanisms through which tropical cyclogenesis occurs are distinctly different from those through which mid-latitude cyclogenesis occurs...
  
  
• tropical cyclone
  Tropical cyclone
  A tropical cyclone is a storm system characterized by a large low-pressure center and numerous thunderstorms that produce strong winds and heavy rain. Tropical cyclones strengthen when water evaporated from the ocean is released as the saturated air rises, resulting in condensation of water vapor...
  
   (tropical storm) (typhoon) (hurricane)
• Tropical Cyclone Formation Alert
  Tropical Cyclone Formation Alert
  A Tropical Cyclone Formation Alert is a bulletin released by the U.S. Navy-operated Joint Typhoon Warning Center in Honolulu, Hawaii or the Naval Maritime Forecast Center in Norfolk, Virginia, warning of the possibility of a tropical cyclone forming from a tropical disturbance that has been...
  
   (TCFA)
• tropical cyclone observation
  Tropical cyclone observation
  Tropical cyclone observation has been carried out over the past couple of centuries in various ways. The passage of typhoons, hurricanes, as well as other tropical cyclones have been detected by word of mouth from sailors recently coming to port or by radio transmissions from ships at sea, from...
  
  
• tropical cyclone prediction model
  Tropical cyclone prediction model
  A tropical cyclone forecast model is a computer program that uses meteorological data to forecast aspects of the future state of tropical cyclones. There are three types of models: statistical, dynamical, or combined statistical-dynamic...
  
  
• tropical cyclone rainfall climatology
  Tropical cyclone rainfall climatology
  A tropical cyclone rainfall climatology is developed to determine rainfall characteristics of past tropical cyclones. A tropical cyclone rainfall climatology can be used to help forecast current or upcoming tropical cyclone impacts. The degree of a tropical cyclone rainfall impact depends upon...
  
  
• tropical cyclone scales
  Tropical cyclone scales
  Tropical systems are officially ranked on one of several tropical cyclone scales according to their maximum sustained winds and in what oceanic basin they are located...
  
  
• Tropical Ocean-Global Atmosphere program
  Tropical Ocean-Global Atmosphere program
  The Tropical Ocean Global Atmosphere program is a component of the World Climate Research Programme aimed specifically at the prediction of climate phenomena on time scales of months to years....
  
   (TOGA)
• tropical rain belt
  Tropical rain belt
  The rainfall, and hence the tropical climate is dominated by the tropical rain belt, which oscillates from the northern to the southern tropics over the course of the year, roughly following the solar equator; it is largely a manifestation of the ITCZ...
  
  
• Tropical Rainfall Measuring Mission
  Tropical Rainfall Measuring Mission
  The Tropical Rainfall Measuring Mission is a joint space mission between NASA and the Japan Aerospace Exploration Agency designed to monitor and study tropical rainfall. The term refers to both the mission itself and the satellite that the mission uses to collect data...
  
   (TRMM)
• Tropical Rainforest Heritage of Sumatra
  Tropical Rainforest Heritage of Sumatra
  The Tropical Rainforest Heritage of Sumatra site was inscribed as a UNESCO World Heritage site in 2004. It comprises three Indonesian national parks on the island of Sumatra: Gunung Leuser National Park, Kerinci Seblat National Park and the Bukit Barisan Selatan National Park...
  
   (in Indonesia)
• (Tropical Research Institute) Smithsonian Tropical Research Institute
  Smithsonian Tropical Research Institute
  The Smithsonian Tropical Research Institute in Panama, the only bureau of the Smithsonian Institution based outside of the United States, is dedicated to understanding biological diversity. What began in 1923 as small field station on Barro Colorado Island in the Panama Canal Zone has developed...
  
   (STRI) (in Panama)
• Tropical Upper Tropospheric Trough
  Tropical Upper Tropospheric Trough
  A tropical upper tropospheric trough , also known as the mid-oceanic trough, is a trough situated in upper-level tropics. Its formation is usually caused by the intrusion of energy and wind from the mid-latitudes into the tropics. It can also develop from the inverted trough adjacent to an upper...
  
   (TUTT)
• tropical waves (African easterly waves)
• tropopause
  Tropopause
  The tropopause is the atmospheric boundary between the troposphere and the stratosphere.-Definition:Going upward from the surface, it is the point where air ceases to cool with height, and becomes almost completely dry...
  
  
• troposphere
  Troposphere
  The troposphere is the lowest portion of Earth's atmosphere. It contains approximately 80% of the atmosphere's mass and 99% of its water vapor and aerosols....
  
  
• Tropospheric Emission Spectrometer
  Tropospheric Emission Spectrometer
  Tropospheric Emission Spectrometer or TES is a satellite instrument designed to measure the state of the earth's troposphere. It is an infrared Fourier Transform spectrometer and provides key data for studying tropospheric chemistry, troposphere-biosphere interaction, and troposphere-stratosphere...
  
   (TES)
• tropospheric ozone
  Tropospheric ozone
  Ozone is a constituent of the troposphere . Photochemical and chemical reactions involving it drive many of the chemical processes that occur in the atmosphere by day and by night...
  
  
• tsunami
  Tsunami
  A tsunami is a series of water waves caused by the displacement of a large volume of a body of water, typically an ocean or a large lake...
  
  
• Tsunami PTSD Center
  Tsunami PTSD Center
  The Tsunami Post Traumatic Stress Disorder Center is a nonprofit institution located in Bangkok, Thailand, committed to the study, treatment and education of PTSD and related mental health issues, many of which are specific to Asia....
  
   (Tsunami Post Traumatic Stress Disorder Center)
• tsunami warning system
  Tsunami warning system
  A Tsunami warning system is used to detect tsunamis in advance and issue warnings to prevent loss of life and damage. It consists of two equally important components: a network of sensors to detect tsunamis and a communications infrastructure to issue timely alarms to permit evacuation of coastal...
  
  

U

• U.S. state temperature extremes
  U.S. state temperature extremes
  The following table lists the highest and lowest temperatures recorded in each state in the United States, in both Fahrenheit and Celsius.The following table lists the highest and lowest temperatures recorded in each state in the United States, in both Fahrenheit and Celsius.The following table...
  
  
• ultraviolet
  Ultraviolet
  Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
  
  
• United States temperature extremes
• UV index
  UV index
  The ultraviolet index or UV Index is an international standard measurement of the strength of the ultraviolet radiation from the sun at a particular place on a particular day...
  
  

W

• water vapor
  Water vapor
  Water vapor or water vapour , also aqueous vapor, is the gas phase of water. It is one state of water within the hydrosphere. Water vapor can be produced from the evaporation or boiling of liquid water or from the sublimation of ice. Under typical atmospheric conditions, water vapor is continuously...
  
  
• weather
  Weather
  Weather is the state of the atmosphere, to the degree that it is hot or cold, wet or dry, calm or stormy, clear or cloudy. Most weather phenomena occur in the troposphere, just below the stratosphere. Weather refers, generally, to day-to-day temperature and precipitation activity, whereas climate...
  
  
• weather lore
  Weather lore
  Weather lore is the body of informal folklore related to the prediction of the weather.It has been a human desire for millennia to make accurate weather predictions. Oral and written history is full of rhymes, anecdotes, and adages meant to guide the uncertain in determining whether the next day...
  
  
• wind
  Wind
  Wind is the flow of gases on a large scale. On Earth, wind consists of the bulk movement of air. In outer space, solar wind is the movement of gases or charged particles from the sun through space, while planetary wind is the outgassing of light chemical elements from a planet's atmosphere into space...
  
  
• windcatcher
  Windcatcher
  A windcatcher is a traditional Persian architectural device used for many centuries to create natural ventilation in buildings. It is not known who first invented the windcatcher, but it still can be seen in many countries today. Windcatchers come in various designs: uni-directional,...
  
  
• Windscale fire
  Windscale fire
  The Windscale fire of 10 October 1957 was the worst nuclear accident in Great Britain's history, ranked in severity at level 5 on the 7-point International Nuclear Event Scale. The two piles had been hurriedly built as part of the British atomic bomb project. Windscale Pile No. 1 was operational in...
  
  
• winter storm
  Winter storm
  A winter storm is an event in which the dominant varieties of precipitation are formed that only occur at low temperatures, such as snow or sleet, or a rainstorm where ground temperatures are low enough to allow ice to form...
  
  
• Winter Storm Warning
  Winter Storm Warning
  A Winter Storm Warning is a statement made by the National Weather Service of the United States which means a winter storm is occurring or is about to occur in the area, usually within 24 hours. Generally, a Winter Storm Warning is issued if at least to or more of snow or or more of snow with...
  
  
• Winter Weather Advisory
  Winter Weather advisory
  A Winter Weather Advisory is issued by the National Weather Service of the United States when a low pressure system produces a combination of winter weather that presents a hazard, but does not meet warning criteria. A Winter Weather Advisory is similar to significant weather advisory, but a...
  
  
• World Asthma Day
  World Asthma Day
  World Asthma Day is an annual event organized by the Global Initiative for Asthma to improve asthma awareness and care around the world. World Asthma Day takes place on the first Tuesday of May. The theme of this year's event is "You Can Control Your Asthma".- External links :* * – Agency for...
  
  
• World Climate Change Conference, Moscow
• World Climate Conference
  World Climate Conference
  The world climate conferences are a series of international meetings, organized by the World Meteorological Organization , about global climate issues. The first two conferences largely focused on climate change in addition to climate research and forecasting...
  
  
• World Climate Programme
  World Climate Programme
  The World Climate Programme was established following the first World Climate Conference in 1979. The major sponsors are the World Meteorological Organization, United Nations Environment Programme, the Intergovernmental Oceanographic Commission of the United Nations Educational, Scientific and...
  
  
• World Climate Report
  World Climate Report
  World Climate Report, a newsletter edited by Patrick Michaels, was produced by the Greening Earth Society, a non-profit organization created by the Western Fuels Association....
  
  
• World Climate Research Programme
  World Climate Research Programme
  The World Climate Research Programme was established in 1980, under the joint sponsorship of International Council for Science and the World Meteorological Organization, and has also been sponsored by the Intergovernmental Oceanographic Commission of UNESCO since 1993. It is a component of the...
  
  
• World Meteorological Organization
  World Meteorological Organization
  The World Meteorological Organization is an intergovernmental organization with a membership of 189 Member States and Territories. It originated from the International Meteorological Organization , which was founded in 1873...
  
   (WMO)
• World Solar Challenge
  World Solar Challenge
  The World Solar Challenge is a solar-powered car race which covers through the Australian Outback, from Darwin to Adelaide.The race attracts teams from around the world, most of which are fielded by universities or corporations although some are fielded by high schools...