Information content of infrared satellite sounding measurements with respect to CO2

Abstract

Information theory is used to study the capabilities of the new-generation satellite infrared sounders [Atmospheric Infrared Sounder (AIRS) and Infrared Atmospheric Sounding Interferometer (IASI)] for retrieving atmospheric carbon dioxide (CO2) and for contrasting these new instruments with the current system of infrared sounders [Television and Infrared Observation Satellite (TIROS) Operational Vertical Sounder/High-Resolution Infrared Radiation Sounder (TOVS/HIRS)]. It is shown that instruments like AIRS and IASI will be able to retrieve column-averaged CO2 mixing ratios with high enough accuracy (order of 1-2 ppmv) to be useful for atmospheric CO2 inversion studies that try to estimate sources and sinks of CO2. On the other hand, the TOVS/HIRS system is only able to retrieve column-averaged CO2 mixing ratios with an accuracy of the same order as the seasonal amplitude of atmospheric CO2 variations (order of 10 ppmv). It is also shown that the constraining a priori covariance matrix has an important effect on what information can be extracted from the observations. © 2004 American Meteorological Society.