Atmospheric infrared sounder

This report summarizes the activities of two Atmospheric Infrared Sounder (AIRS) team members during the first half of 1995. Changes to the microwave first-guess algorithm have separated processing of Advanced Microwave Sounding Unit A (AMSU-A) from AMSU-B data so that the different spatial resolutions of the two instruments may eventually be considered. Two-layer cloud simulation data was processed with this algorithm. The retrieved water vapor column densities and liquid water are compared. The information content of AIRS data was applied to AMSU temperature profile retrievals in clear and cloudy atmospheres. The significance of this study for AIRS/AMSU processing lies in the improvement attributable to spatial averaging and in the good results obtained with a very simple algorithm when all of the channels are used. Uncertainty about the availability of either a Microwave Humidity Sensor (MHS) or AMSU-B for EOS has motivated consideration of possible low-cost alternative designs for a microwave humidity sensor. One possible configuration would have two local oscillators (compared to three for MHS) at 118.75 and 183.31 GHz. Retrieval performances of the two instruments were compared in a memorandum titled 'Comparative Analysis of Alternative MHS Configurations', which is attached.