Mid-tropospheric CO2 retrieval from AIRS observations in the tropical zone
Cyril Crevoisier, Alain Chédin, Sylvain Heilliette, Noëlle A. Scott, Soumia Serrar and Raymond Armante
EGU 1st general assembly, Nice, 25 - 30 April 2004
The new 2378 channel high spectral resolution NASA/Aqua/Atmospheric Infrared Sounder (AIRS) launched in May 2002 is used to retrieve mean concentration of atmospheric carbon dioxide (CO2).A reduced set of channels presenting high sensitivity to CO2 variations and no sensitivity to other atmospheric components and well covering the mid-troposphere (from 700 hPa to the tropopause) is first selected using the Optimum Sensitive Profile method. A detection of clear fields of view based on AIRS and Advanced Microwave Sounding Unit (AMSU) observations is then performed. The resulting AIRS measurements, sensitive to both temperature and CO2 variations, and AMSU measurements, only sensitive to temperature variations, are used in synergy, in order to separate the two effects. Use is made of a neural network non-linear inversion scheme that has already proven its efficiency in the retrieval of CO2 concentration from NOAA TOVS polar satellites. Maps of monthly CO2 concentration are obtained in the topical zone [20N ; 20S] from April 2003 to now, night time. The retrieved variations of CO2 show good agreement with in situ measurements made by commercial airliners at the same altitude range. These retrievals might improve carbon flux inversion models, with large potential benefits for global carbon cycle research.