Assimilation of total column CO observations from the MAPS instrument.

Carbon monoxide (CO) plays a key role in regulating the oxidizing potential of the troposphere through the hydroxyl (OH) radical. Oxidation of OH is the primary sink for tropospheric methane and also a sink for a number of hydrofluorocarbons. OH also serves to convert nitrogen oxides and sulfur dioxide to nitric acid and sulfuric acid, respectively. However, current remote sensing techniques cannot measure OH, but several instruments were developed to measure CO which largely controls OH. MAPS (Measurement of Air Pollution from Satellites) was the first instrument of this kind developed, and provided total column CO measurements from the space shuttle in April and October 1994. The measurement technique is similar to that used for the MOPITT instrument scheduled to fly this summer on the EOS AM-1 platform. A three-dimensional tropospheric data assimilation system has been developed using parametrized chemistry of source and sink of CO. Results using the PSAS scheme with flow-dependent error covariances will be presented.