Upper Atmospheric Models
Encyclopedia
Most climate models simulate a region of the Earth's atmosphere from the surface to the stratopause
. There also exist numerical models which simulate the wind, temperature and composition of the Earth's tenuous upper atmosphere
, from the mesosphere
to the exosphere
, including the ionosphere
. This region is affected strongly by the 11 year Solar cycle
through variations in solar UV/EUV/Xray radiation and solar wind
leading to high latitude particle precipitation and aurora
. It has been proposed that these phenomena may have an effect on the lower atmosphere, and should therefore be included in simulations of climate change. For this reason there has been a drive in recent years to create "whole atmosphere" models to investigate whether or not this is the case.
A jet stream
perturbation model is employed by Weather Logistics UK, which simulates the diversion of the air streams in the upper atmosphere
. North Atlantic
air flow modelling is simulated by combining a monthly jet stream
climatology input calculated at 20 to 30°W, with different blocking high patterns
. The jet stream input is generated by thermal wind
balance calculations at 316mbars (6 to 9km aloft) in the mid-latitude range from 40 to 60°N. Long term blocking patterns are determined by the weather forecaster
, who identifies the likely position and strength of North Atlantic Highs
from synoptic charts
, the North Atlantic Oscillation
(NAO) and El Niño-Southern Oscillation
(ENSO) patterns. The model is based on the knowledge that low pressure systems at the surface are steered by the fast ribbons (jet streams) of air in the upper atmosphere. The jet stream - blocking interaction model simulation examines the sea surface temperature
field using data from NOAA
tracked along the ocean on a path to the British Isles. The principal theory suggests that long term weather patterns act on longer time scales, so large blocking patterns are thought to appear in a similar locations repeatedly over several months. With a good knowledge of blocking high patterns, the model performs with an impressive accuracy that is useful to the end user.
The modelling undertaken at Weather Logistics UK produces regional-seasonal predictions that are probabilistic
in nature. Two different blocking sizes are used for the modelling, located at two different locations. The four possible blocking diversions are then ranked in an order, to be combined by logistic regression
and generate the appropriate likelihoods of weather events on seasonal time-scales. The raw output consists of 22 different weather conditions for each season that are compared to the average atmospheric conditions. A global warming
bias and 1961-1990 climatology
of regional British Isles temperatures are added to the anomaly value to produce a final temperature prediction. The seasonal weather forecasts at Weather Logistics UK comprise of several additional weather components (derivatives) including: precipitation anomlies, storm tracks, air flow trajectories, heating degree days
for household utility bills, cooling degree days, heat wave
and the snow day
odds.
According to a report in New Scientist many researchers are in consensus that Rossby waves are acting against the jet stream’s usual pattern and holding it in place. Upper atmospheric studies using National Oceanic and Atmospheric Admistration (NOAA) data indicates that during July 2010 these upper air stream patterns were most frequently observed in the Northern Hemisphere. Examination of the climatology data over the same period of time indicates that these wild planetary wave meanderings are not a normal aspect of our regional climate patterns. Meanwhile, ongoing research studies at the University of Reading show that unusual patterns in the polar jet stream are more common during a period of low activity in the solar cycle
when the observed sun spot
activity and their associated solar flares are at their minimum. The link between low solar activity and enhanced blocking patterns is associated with an increase in the prevalence of cold weather patterns during the European Winter. Another possible explanation for the observed increase in blocking patterns is natural variability, through the chaotic character of the large-scale Ocean currents that flow across the surface of the tropical Pacific.
Some further links of interest:
Stratopause
The stratopause is the level of the atmosphere which is the boundary between two layers, stratosphere and the mesosphere...
. There also exist numerical models which simulate the wind, temperature and composition of the Earth's tenuous upper 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...
, from 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...
to the 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...
, including the 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...
. This region is affected strongly by the 11 year 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...
through variations in solar UV/EUV/Xray radiation and 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...
leading to high latitude particle precipitation and aurora
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...
. It has been proposed that these phenomena may have an effect on the lower atmosphere, and should therefore be included in simulations of climate change. For this reason there has been a drive in recent years to create "whole atmosphere" models to investigate whether or not this is the case.
A jet stream
Jet stream
Jet streams are fast flowing, narrow air currents found in the atmospheres of some planets, including Earth. The main jet streams are located near the tropopause, the transition between the troposphere and the stratosphere . The major jet streams on Earth are westerly winds...
perturbation model is employed by Weather Logistics UK, which simulates the diversion of the air streams in the upper 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...
. North Atlantic
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
air flow modelling is simulated by combining a monthly jet stream
Jet stream
Jet streams are fast flowing, narrow air currents found in the atmospheres of some planets, including Earth. The main jet streams are located near the tropopause, the transition between the troposphere and the stratosphere . The major jet streams on Earth are westerly winds...
climatology input calculated at 20 to 30°W, with different blocking high patterns
Block (meteorology)
Blocks in meteorology are large scale patterns in the atmospheric pressure field that are nearly stationary, effectively "blocking" or redirecting migratory cyclones. They are also known as blocking highs or blocking anticyclones...
. The jet stream input is generated by thermal wind
Thermal wind
The thermal wind is a vertical shear in the geostrophic wind caused by a horizontal temperature gradient. Its name is a misnomer, because the thermal wind is not actually a wind, but rather a wind shear.- Physical Intuition :...
balance calculations at 316mbars (6 to 9km aloft) in the mid-latitude range from 40 to 60°N. Long term blocking patterns are determined by the weather forecaster
Weather forecasting
Weather forecasting is the application of science and technology to predict the state of the atmosphere for a given location. Human beings have attempted to predict the weather informally for millennia, and formally since the nineteenth century...
, who identifies the likely position and strength of North Atlantic Highs
Block (meteorology)
Blocks in meteorology are large scale patterns in the atmospheric pressure field that are nearly stationary, effectively "blocking" or redirecting migratory cyclones. They are also known as blocking highs or blocking anticyclones...
from synoptic charts
Weather map
A weather map displays various meteorological features across a particular area at a particular point in time. Such maps have been in use since the mid-19th century and are used for research and weather forecasting purposes. Maps using isotherms show temperature gradients, which can help locate...
, the North Atlantic Oscillation
North Atlantic oscillation
The North Atlantic oscillation is a climatic phenomenon in the North Atlantic Ocean of fluctuations in the difference of atmospheric pressure at sea level between the Icelandic low and the Azores high. Through east-west oscillation motions of the Icelandic low and the Azores high, it controls the...
(NAO) and El Niño-Southern Oscillation
El Niño-Southern Oscillation
El Niño/La Niña-Southern Oscillation, or ENSO, is a quasiperiodic climate pattern that occurs across the tropical Pacific Ocean roughly every five years...
(ENSO) patterns. The model is based on the knowledge that low pressure systems at the surface are steered by the fast ribbons (jet streams) of air in the upper atmosphere. The jet stream - blocking interaction model simulation examines the 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...
field using data from NOAA
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...
tracked along the ocean on a path to the British Isles. The principal theory suggests that long term weather patterns act on longer time scales, so large blocking patterns are thought to appear in a similar locations repeatedly over several months. With a good knowledge of blocking high patterns, the model performs with an impressive accuracy that is useful to the end user.
The modelling undertaken at Weather Logistics UK produces regional-seasonal predictions that are probabilistic
Probabilistic forecasting
Probabilistic forecasting summarises what is known, or opinions about, future events. In contrast to a single-valued forecasts , probabilistic forecasts assign a probability to each of a number of different outcomes,...
in nature. Two different blocking sizes are used for the modelling, located at two different locations. The four possible blocking diversions are then ranked in an order, to be combined by logistic regression
Logistic regression
In statistics, logistic regression is used for prediction of the probability of occurrence of an event by fitting data to a logit function logistic curve. It is a generalized linear model used for binomial regression...
and generate the appropriate likelihoods of weather events on seasonal time-scales. The raw output consists of 22 different weather conditions for each season that are compared to the average atmospheric conditions. A 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...
bias and 1961-1990 climatology
Climate of the United Kingdom
The United Kingdom straddles the geographic mid-latitudes between 50-60 N from the equator. It is also positioned on the western seaboard of Eurasia, the world's largest land mass. These boundary conditions allow convergence between moist maritime air and dry continental air...
of regional British Isles temperatures are added to the anomaly value to produce a final temperature prediction. The seasonal weather forecasts at Weather Logistics UK comprise of several additional weather components (derivatives) including: precipitation anomlies, storm tracks, air flow trajectories, heating degree days
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...
for household utility bills, cooling degree days, 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...
and the snow day
Weather-related cancellation
A weather-related cancellation or delay is when an institution, operation, or event is closed, canceled, or delayed as a result of inclement weather conditions...
odds.
According to a report in New Scientist many researchers are in consensus that Rossby waves are acting against the jet stream’s usual pattern and holding it in place. Upper atmospheric studies using National Oceanic and Atmospheric Admistration (NOAA) data indicates that during July 2010 these upper air stream patterns were most frequently observed in the Northern Hemisphere. Examination of the climatology data over the same period of time indicates that these wild planetary wave meanderings are not a normal aspect of our regional climate patterns. Meanwhile, ongoing research studies at the University of Reading show that unusual patterns in the polar jet stream are more common during a period of low activity in the 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...
when the observed sun spot
Sun SPOT
Sun SPOT is a wireless sensor network mote developed by Sun Microsystems. The device is built upon the IEEE 802.15.4 standard...
activity and their associated solar flares are at their minimum. The link between low solar activity and enhanced blocking patterns is associated with an increase in the prevalence of cold weather patterns during the European Winter. Another possible explanation for the observed increase in blocking patterns is natural variability, through the chaotic character of the large-scale Ocean currents that flow across the surface of the tropical Pacific.
External links
Four examples of upper atmospheric models are:- NCAR TIE-GCM (97 to ~450km), NCAR TIME-GCM (30 to ~450km)
- UCL CTIP (80km to ~ 450km), UCL CMAT (30km to ~ 450km)
- UAM is the global mathematical model of the Earth's upper atmosphere (mesosphere, thermosphere, ionosphere, plasmasphere and inner magnetosphere).
- Weather Logistics UK: Jet stream - Blocking interaction model (5 to 9km) jet stream - blocking diversion model to simulate large scale and long term air flow for the British Isles. Incorporates sea surface temperature data from NOAA and a monthly jet stream climatology.
Some further links of interest:
- 'Blocked' jetstream to blame for freak weather in Russia and Pakistan, say scientists.
- Are cold winters in Europe associated with low solar activity? M Lockwood et al 2010 Environ. Res. Lett. 5 024001
- Blocking ‘Cogs’ Stall Seasonal Weather C Nankervis, Weather Logistics UK, Published November 22nd 2011.