Improved determination of surface and atmospheric temperatures using only shortwave AIRS channels: The AIRS Version-6 retrieval algorithm

Joel Susskind, John Blaisdell, Lena Iredell
2010 2010 IEEE International Geoscience and Remote Sensing Symposium  
AIRS was launched on EOS Aqua on May 4, 2002 together with ASMU-A and HSB to form a next generation polar orbiting infrared and microwave atmosphere sounding system (Pagano et al 2003). The theoretical approach used to analyze AIRS/AMSU/HSB data in the presence of clouds in the AIRS Science Team Version 3 at-launch algorithm, and that used in the Version 4 post-launch algorithm, have been published previously. Significant theoretical and practical improvements have been made in the analysis of
more » ... in the analysis of AIRS/AMSU data since the Version 4 algorithm. Most of these have already been incorporated in the AIRS Science Team Version 5 algorithm (Susskind et al 2010), now being used operationally at the Goddard DISC. The AIRS Version 5 retrieval algorithm contains three significant improvements over Version 4. Improved physics in Version 5 allowed for use of AIRS clear column radiances in the entire 4.3 m CO 2 absorption band in the retrieval of temperature profiles T(p) during both day and night. Tropospheric sounding 15 m CO 2 observations were used primarily in the generation of clear column radiances for all channels. This new approach allowed for the generation of accurate Quality Controlled values of and T(p) under more stressing cloud conditions. Secondly, Version 5 contained a new methodology to provide accurate case-bycase error estimates for retrieved geophysical parameters and for channel-by-channel clear column radiances. Thresholds of these error estimates are used in a new approach for Quality Control. Finally, Version 5 contained for the first time an approach to provide AIRS soundings in partially cloudy conditions that does not require use of any microwave data. This new AIRS Only sounding methodology was developed as a backup to AIRS Version 5 should the AMSU-A instrument fail. Susskind et al 2010 shows that Version 5 AIRS Only sounding are only slightly degraded from the AIRS/AMSU soundings, even at large fractional cloud cover. Significant further progress has been made by the AIRS Science Team since the delivery of the AIRS Version 5 retrieval algorithm to form the AIRS Science Team Version 6 AIRS/AMSU retrieval algorithm. The Version 6 retrieval algorithm is for the most part very similar to Version 5 with one major exception. As in Version 5, the generation of cloud cleared radiances for all channels is performed using observed radiances for longwave 15 m and 11 m channels. Tropospheric temperature profiles were retrieved in Version 5
doi:10.1109/igarss.2010.5650538 dblp:conf/igarss/SusskindBI10 fatcat:2fuhv2xyvrfm3fveesazvj2ooa