Atmospheric Infrared Sounder
Encyclopedia
The Atmospheric Infrared Sounder (AIRS) is one of six instruments flying on board NASA’s Aqua satellite
, launched on May 4, 2002. The instrument is designed to support climate
research and improve weather
forecasting.
Working in combination with its partner microwave
instrument, the Advanced Microwave Sounding Unit
(AMSU-A), AIRS observes the global water
and energy cycles, climate
variation and trends, and the response of the climate system to increased greenhouse gases. AIRS uses infrared
technology to create three-dimensional maps of air and surface temperature, water vapor
, and cloud
properties. AIRS can also measure trace greenhouse gases such as ozone
, carbon monoxide
, carbon dioxide
, and methane
.
AIRS and AMSU-A share the Aqua satellite with the Moderate Resolution Imaging Spectroradiometer (MODIS
), Clouds and the Earth's Radiant Energy System (CERES), and the Advanced Microwave Scanning Radiometer-EOS (AMSR-E). Aqua is part of NASA's "A-train," a series of high-inclination, Sun-synchronous satellites in low Earth orbit designed to make long-term global observations of the land surface, biosphere
, solid Earth, atmosphere
, and ocean
.
AIRS data is free and available to the public through the Goddard Earth Sciences Data Information and Services Center.
NASA's Jet Propulsion Laboratory
in Pasadena, California, manages AIRS for NASA's Science Mission Directorate
in Washington, D.C.
AIRS measures the infrared
brightness coming up from Earth's surface and from the atmosphere. Its scan mirror rotates around an axis along the line of flight and directs infrared energy from the Earth into the instrument. As the spacecraft moves along, this mirror sweeps the ground creating a scan swath that extends roughly 800 kilometers on either side of the ground track. Within the instrument, an advanced, high-resolution spectrometer
separates the infrared
energy into wavelength
s.
Each infrared wavelength is sensitive to temperature and water vapor over a range of heights in the atmosphere
, from the surface up into the stratosphere
. By having multiple infrared detectors, each sensing a particular wavelength, a temperature profile, or sounding of the atmosphere, can be made. While prior space instruments had only 15 detectors, AIRS has 2378. This greatly improves the accuracy, making it comparable to measurements made by weather balloon
s.
Thick clouds act like a wall to the infrared energy measured by AIRS. However, microwave instruments on board Aqua can see through the clouds with limited accuracy. Using a special computer algorithm
, data from AIRS and the microwave instruments are combined to provide highly accurate measurements in all cloud conditions resulting in a daily global snapshot of the state of the atmosphere.
AIRS primary scientific achievement has been to improve weather prediction and provide new information on the water and energy cycle. The instrument also yields information on several important greenhouse gases.
Weather and climate forecasting
AIRS data are used by weather forecasting centers around the world. By incorporating AIRS measurements into their models, forecasters have been able to extended reliable mid-range weather forecasts by more than six hours. AIRS data have also improved forecasts of the location and magnitude of predicted storms.
AIRS temperature and water vapor profiles are available in real time to regional weather forecasters, providing twice-daily weather measurements for the entire Pacific Ocean, once in the morning and once in the evening.
AIRS measurements form a "fingerprint" of the state of the atmosphere for a given time and place that can be used as a climate data record for future generations. They have become important tools for understanding current climate and increasing the ability to predict the future.
Atmospheric Composition, Greenhouse Gases, and Air Quality
AIRS maps the concentration of carbon dioxide
and methane
globally. Its ability to provide simultaneous observations of the Earth's atmospheric temperature, water vapor, ocean surface temperature, and land surface temperature and infrared spectral emissivity, as well as humidity, clouds and the distribution of greenhouse gases, makes AIRS/AMSU a very useful space instrument to observe and study the response of the atmosphere to increased greenhouse gases.
The instrument can detect carbon monoxide
emissions from the burning of plant materials and animal waste by humans in rainforests and large cities. It can follow giant plumes of this gas moving across the planet from these large burns, allowing scientists to better monitor pollution transport patterns.
AIRS provides a global daily 3-D view of Earth's ozone layer
, showing how ozone is transported. The instrument also gives scientists their best view of atmospheric ozone in the Antarctic region during the polar winter.
AIRS is also able to identify concentrations of sulfur dioxide and dust.
Aqua (satellite)
Aqua is a multi-national NASA scientific research satellite in orbit around the Earth, studying the precipitation, evaporation, and cycling of water. It is the second major component of the Earth Observing System preceded by Terra and followed by Aura .The name "Aqua" comes from the Latin word...
, launched on May 4, 2002. The instrument is designed to support 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...
research and improve 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...
forecasting.
Working in combination with its partner microwave
Microwave
Microwaves, a subset of radio waves, have wavelengths ranging from as long as one meter to as short as one millimeter, or equivalently, with frequencies between 300 MHz and 300 GHz. This broad definition includes both UHF and EHF , and various sources use different boundaries...
instrument, the Advanced Microwave Sounding Unit
Advanced Microwave Sounding Unit
The Advanced microwave sounding unit is a multi-channel microwave radiometer installed on meteorological satellites. The instrument examines several bands of microwave radiation from the atmosphere to perform atmospheric sounding of temperature and moisture levels.-Products:Level-1 radiance data...
(AMSU-A), AIRS observes the global water
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...
and energy cycles, 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...
variation and trends, and the response of the climate system to increased greenhouse gases. AIRS uses 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...
technology to create three-dimensional maps of air and surface temperature, 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...
, and 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...
properties. AIRS can also measure trace greenhouse gases such as 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...
, 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...
, carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
, and methane
Methane
Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...
.
AIRS and AMSU-A share the Aqua satellite with the Moderate Resolution Imaging Spectroradiometer (MODIS
MODIS
The Moderate-resolution Imaging Spectroradiometer is a payload scientific instrument launched into Earth orbit by NASA in 1999 on board the Terra Satellite, and in 2002 on board the Aqua satellite...
), Clouds and the Earth's Radiant Energy System (CERES), and the Advanced Microwave Scanning Radiometer-EOS (AMSR-E). Aqua is part of NASA's "A-train," a series of high-inclination, Sun-synchronous satellites in low Earth orbit designed to make long-term global observations of the land surface, biosphere
Biosphere
The biosphere is the global sum of all ecosystems. It can also be called the zone of life on Earth, a closed and self-regulating system...
, solid Earth, 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...
, and ocean
Ocean
An ocean is a major body of saline water, and a principal component of the hydrosphere. Approximately 71% of the Earth's surface is covered by ocean, a continuous body of water that is customarily divided into several principal oceans and smaller seas.More than half of this area is over 3,000...
.
AIRS data is free and available to the public through the Goddard Earth Sciences Data Information and Services Center.
NASA's Jet Propulsion Laboratory
Jet Propulsion Laboratory
Jet Propulsion Laboratory is a federally funded research and development center and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, United States. The facility is headquartered in the city of Pasadena on the border of La Cañada Flintridge and Pasadena...
in Pasadena, California, manages AIRS for NASA's Science Mission Directorate
Science Mission Directorate
The Science Mission Directorate of the National Aeronautics and Space Administration engages the United States’ science community, sponsors scientific research, and develops and deploys satellites and probes in collaboration with NASA’s partners around the world to answer fundamental questions...
in Washington, D.C.
Technology
The term "sounder" in AIRS's name refers to the fact that the instrument measures temperature and water vapor as a function of height.AIRS measures the 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...
brightness coming up from Earth's surface and from the atmosphere. Its scan mirror rotates around an axis along the line of flight and directs infrared energy from the Earth into the instrument. As the spacecraft moves along, this mirror sweeps the ground creating a scan swath that extends roughly 800 kilometers on either side of the ground track. Within the instrument, an advanced, high-resolution spectrometer
Spectrometer
A spectrometer is an instrument used to measure properties of light over a specific portion of the electromagnetic spectrum, typically used in spectroscopic analysis to identify materials. The variable measured is most often the light's intensity but could also, for instance, be the polarization...
separates the 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...
energy into wavelength
Wavelength
In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...
s.
Each infrared wavelength is sensitive to temperature and water vapor over a range of heights in the 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 surface up into the 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...
. By having multiple infrared detectors, each sensing a particular wavelength, a temperature profile, or sounding of the atmosphere, can be made. While prior space instruments had only 15 detectors, AIRS has 2378. This greatly improves the accuracy, making it comparable to measurements made by weather balloon
Weather balloon
A weather or sounding balloon is a balloon which carries instruments aloft to send back information on atmospheric pressure, temperature, humidity and wind speed by means of a small, expendable measuring device called a radiosonde...
s.
Thick clouds act like a wall to the infrared energy measured by AIRS. However, microwave instruments on board Aqua can see through the clouds with limited accuracy. Using a special computer algorithm
Algorithm
In mathematics and computer science, an algorithm is an effective method expressed as a finite list of well-defined instructions for calculating a function. Algorithms are used for calculation, data processing, and automated reasoning...
, data from AIRS and the microwave instruments are combined to provide highly accurate measurements in all cloud conditions resulting in a daily global snapshot of the state of the atmosphere.
AIRS Science and Applications
AIRS and its companion microwave sounder AMSU observe the entire atmospheric column from Earth’s surface to the top of the atmosphere. The primary data they return is the infrared spectrum in 2378 individual frequencies. The infrared spectrum is rich in information on numerous gases in the atmosphere.AIRS primary scientific achievement has been to improve weather prediction and provide new information on the water and energy cycle. The instrument also yields information on several important greenhouse gases.
AIRS data are used by weather forecasting centers around the world. By incorporating AIRS measurements into their models, forecasters have been able to extended reliable mid-range weather forecasts by more than six hours. AIRS data have also improved forecasts of the location and magnitude of predicted storms.
AIRS temperature and water vapor profiles are available in real time to regional weather forecasters, providing twice-daily weather measurements for the entire Pacific Ocean, once in the morning and once in the evening.
AIRS measurements form a "fingerprint" of the state of the atmosphere for a given time and place that can be used as a climate data record for future generations. They have become important tools for understanding current climate and increasing the ability to predict the future.
Atmospheric Composition, Greenhouse Gases, and Air Quality
AIRS maps the concentration of carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
and methane
Methane
Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...
globally. Its ability to provide simultaneous observations of the Earth's atmospheric temperature, water vapor, ocean surface temperature, and land surface temperature and infrared spectral emissivity, as well as humidity, clouds and the distribution of greenhouse gases, makes AIRS/AMSU a very useful space instrument to observe and study the response of the atmosphere to increased greenhouse gases.
The instrument can detect 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...
emissions from the burning of plant materials and animal waste by humans in rainforests and large cities. It can follow giant plumes of this gas moving across the planet from these large burns, allowing scientists to better monitor pollution transport patterns.
AIRS provides a global daily 3-D view of Earth's 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...
, showing how ozone is transported. The instrument also gives scientists their best view of atmospheric ozone in the Antarctic region during the polar winter.
AIRS is also able to identify concentrations of sulfur dioxide and dust.