Understanding the dynamics of weather and climate, the transport and distribution of atmospheric chemical agents, and the patterns of Earth's rainfall and evaporation requires precise knowledge of global atmospheric circulation, temperature profiles, and water vapor content. AIRS and its partner instrument AMSU are observing and characterizing the entire atmospheric column from Earth's surface to the top of the atmosphere in terms of surface emissivity and temperature, atmospheric temperature and humidity profiles, cloud amount and height, and spectral outgoing infrared radiation. These data and scientific investigations will answer long-standing questions about the exchange and transformation of energy and radiation in the atmosphere and at Earth’s surface.
Determination of factors that control the global energy and water cycles
The study of the global hydrologic cycle and its coupling to the energy cycle is a key to understanding the major driving forces of the Earth’s climate system. AIRS and AMSU are measuring the major components of these driving forces including the thermal structure of the surface and the atmosphere, the outgoing longwave infrared radiation, and the atmospheric water vapor content.
Investigation of atmosphere-surface interactions
The high spectral resolution of AIRS provides several spectrally transparent window channels that observe Earth's surface with minimal contamination by the atmosphere and allows for the determination of accurate surface temperature and infrared spectral emissivity. AIRS' narrow spectral channels in the short-wavelength infrared region observe the atmospheric layers near the Earth’s surface with the highest vertical resolution possible by passive remote sensing. AIRS' observations enable investigations of the fluxes of energy and water vapor between the atmosphere and the surface, along with their effect on climate.
Improving numerical weather prediction
Numerical weather prediction models have now progressed to the point where they can predict atmospheric temperature profiles to an accuracy of 2 K, which is equivalent to the accuracy of current satellite data. Further improvement in our knowledge of temperature profiles is essential in order to improve forecasting accuracy. AIRS/AMSU/HSB temperature profiles with radiosonde accuracy of 1 K in 1 km-thick layers are key to improving the accuracy and extending the range of weather forecasts.
Detection of the effects of increased greenhouse gases
AIRS maps the concentration of carbon dioxide and methane globally. AIRS also provides simultaneous observations of the Earth’s atmospheric temperature, ocean surface temperature, and land surface temperature and infrared spectral emissivity, as well as humidity, clouds and the distribution of greenhouse gases. This makes AIRS/AMSU a primary space instrument to observe and study the response of the atmosphere to increased greenhouse gases.
Assessing climate variations and feedbacks
The accuracy and high spectral resolution of AIRS provide a powerful new tool for climate studies. AIRS’ high resolution infrared coverage from 3.74 to 15 μm give researchers the ability to validate numerical models and study climate processes. For example, emission to space by strong and weak water vapor lines is a critical climate feedback mechanism in the middle and lower troposphere. Numerical models must reproduce such lines as an indication of their ability to describe the climate system.