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For airmass in astronomy
Astronomy

Astronomy is the science of Astronomical object and Phenomenon that originate outside the Earth's atmosphere . It is concerned with the evolution, physics, chemistry, meteorology, and motion of celestial objects, as well as the physical cosmology....
 and photovoltaics, see airmass
Airmass

In astronomy, airmass is the optical path length through Earth's atmosphere for light from a celestial source. As it passes through the atmosphere, light is attenuated by scattering and absorption ; the more atmosphere through which it passes, the greater the attenuation....
.


In meteorology
Meteorology

Meteorology is the interdisciplinary scientific study of the Earth's atmosphere that focuses on weather processes and forecasting . Studies in the field stretch back millennia, though significant progress in meteorology did not occur until the eighteenth century....
, an air mass is a large volume of air
AIR

Air is the part of Earth's atmosphere that humans breath and as such Air .Air may also refer to:...
 that have characteristics of temperature
Temperature

In physics, temperature is a physical property of a Physical system that underlies the common notions of hot and cold; something that feels hotter generally has the greater temperature....
 and water vapor
Water vapor

Water vapor or water vapour , also aqueous vapor, is the gas phase of water . Water vapor is one Phase of the water cycle within the hydrosphere....
 content. Air masses cover many hundreds or thousands of square miles, and slowly change in accordance with the surface below them. They have continental and maritime source regions, with different temperature and moisture characteristics.






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For airmass in astronomy
Astronomy

Astronomy is the science of Astronomical object and Phenomenon that originate outside the Earth's atmosphere . It is concerned with the evolution, physics, chemistry, meteorology, and motion of celestial objects, as well as the physical cosmology....
 and photovoltaics, see airmass
Airmass

In astronomy, airmass is the optical path length through Earth's atmosphere for light from a celestial source. As it passes through the atmosphere, light is attenuated by scattering and absorption ; the more atmosphere through which it passes, the greater the attenuation....
.


In meteorology
Meteorology

Meteorology is the interdisciplinary scientific study of the Earth's atmosphere that focuses on weather processes and forecasting . Studies in the field stretch back millennia, though significant progress in meteorology did not occur until the eighteenth century....
, an air mass is a large volume of air
AIR

Air is the part of Earth's atmosphere that humans breath and as such Air .Air may also refer to:...
 that have characteristics of temperature
Temperature

In physics, temperature is a physical property of a Physical system that underlies the common notions of hot and cold; something that feels hotter generally has the greater temperature....
 and water vapor
Water vapor

Water vapor or water vapour , also aqueous vapor, is the gas phase of water . Water vapor is one Phase of the water cycle within the hydrosphere....
 content. Air masses cover many hundreds or thousands of square miles, and slowly change in accordance with the surface below them. They have continental and maritime source regions, with different temperature and moisture characteristics. Weather front
Weather front

A weather front is a boundary separating two air mass of different density, and is the principal cause of meteorological phenomenon. In surface weather analysis, fronts are depicted using various colored lines and symbols, depending on the type of front....
s separate air masses with different density (temperature and/or moisture) characteristics.

Classification and Notation

Air masses are classified according to their approximate environmental origin. An air mass is classified as Arctic
Arctic

The Arctic is the region around the Earth's North Pole, opposite the Antarctica region around the South Pole. The Arctic includes the Arctic Ocean and parts of Canada, Greenland , Russia, the United States , Iceland, Norway, Sweden and Finland....
, Polar
Polar region

Earth polar regions are the areas of the globe surrounding the geographical pole also known as Geographical zone. 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....
, Tropical
Tropics

The Tropics, seated in the equatorial regions of the world, are limited in latitude by the Tropic of Cancer in the northern hemisphere at approximately 23?26' N latitude, and the Tropic of Capricorn in the southern hemisphere at 23?26' S latitude....
, or Equator
Equator

The equator is the intersection of the Earth's surface with the Plane perpendicular to the Earth's rotation and containing the Earth's center of mass....
ial. It is also classified as either maritime or continental
Continental

Continental is the adjective form of continent. Continental may refer to:*Geography:** Continental climate, a type of climate** Continental Europe, or various terms relating to continental Europe such as continental breakfast and continental lifestyle...
. Maritime air is a moist air mass, whereas continental air is relatively dry.

Air masses are noted on some weather charts using a particular system of notation. However, air mass terminology is somewhat subjective, that is, it is not defined by any definite, universally-accepted quantitative parameters. It is used primarily for general descriptive purposes in meteorological discussions.

Air masses of oceanic origin are denoted with a lower-case "m" ("maritime"), while air masses of continental origin are denoted with a lower-case "c" ("continental"). Air masses are also denoted as either Arctic (upper-case "A", or "AA" for Antarctic air masses), polar (upper-case "P"), tropical (upper-case "T"), or equatorial (upper-case "E"). These two sets of attributes are used in combinations depending on the air mass being described. For instance, an air mass originating over the desert southwest of the United States in summer may be designated "cT". An air mass originating over northern Siberia in winter may be indicated as "cA".

In older charts, an upper case "S" was occasionally used to denote something called a "superior" air mass. This was regarded as an adiabatically drying and warming air mass descending from aloft. In South Asia, an upper case "M" (for "monsoon") has been occasionally used to denote an air mass within the summer monsoon
Monsoon

A monsoon is a seasonal prevailing wind that lasts for several months. The term was first used in English in India, Bangladesh, Pakistan, and neighboring countries to refer to the big seasonal winds blowing from the Indian Ocean and Arabian Sea in the southwest bringing heavy rainfall to the region....
 regime in that region.

The stability of an air mass may be shown using a third letter, either "k" (air mass colder than the surface below it) or "w" (air mass warmer than the surface below it). An example of this might be a polar air mass blowing over the Gulf Stream, denoted as "cPk". Occasionally, especially on older charts, one may also encounter the use of an apostrophe or "degree tick" denoting that a given air mass having the same notation as another it is replacing is colder than the replaced air mass (usually for polar air masses). For example, a series of fronts over the Pacific might show an air mass denoted mPk followed by another denoted mPk'.

Another convention utilizing these symbols is the indication of modification or transformation of one type to another. For instance, an Arctic air mass blowing out over the Gulf of Alaska may be shown as "cA-mPk". Yet another convention indicates the layering of air masses in certain situations. For instance, the overrunning of a polar air mass by an air mass from the Gulf of Mexico over the Central United States might be shown with the notation "mT/cP" (sometimes using a horizontal line as in fraction notation).

Movement and fronts

Air mass terms refer to the fact that air masses acquire characteristics from a given region which they may occupy for any significant length of time. For example, Polar air masses form during the northern winter as intense nighttime radiation and loss of daylight chills the air to great depths, and maritime air masses generally form over oceans and seas where widespread evaporation occurs. When air masses move into regions with different environmental conditions, they are modified. Even without movement, air masses can vary gradually over distance, with one type gradually becoming another. The boundary between two air masses can also be comparatively sharp. Where it is, the boundary is termed a "front
Weather front

A weather front is a boundary separating two air mass of different density, and is the principal cause of meteorological phenomenon. In surface weather analysis, fronts are depicted using various colored lines and symbols, depending on the type of front....
". Fronts are often characterized by inclement weather, and are usually associated with areas of low atmospheric pressure termed frontal systems.

See also

  • Solar irradiance
  • Spatial Synoptic Classification system
    Spatial Synoptic Classification system

    Based upon the Bergeron air mass classification scheme is the Spatial Synoptic Classification system, or SSC. There are six categories within the SSC scheme: Dry Polar , Dry Moderate , Dry Tropical , Moist Polar , Moist Moderate , and Moist Tropical ....