Integrating MOPITT and Aircraft Observations to Estimate Asian CO Emission Sources

Satellite and aircraft observations of trace species provide independent top-down constraints on emissions. The integration of these data sets in a formal inverse model framework requires careful characterization of their error covariances. Daily MOPITT satellite observations and CO data from the TRACE-P aircraft mission over the NW Pacific are applied here to the regional estimation of emissions from Asia for the spring of 2001. We use the GEOS-CHEM global 3-D model of atmospheric chemistry as the forward model. A priori estimates of Asian emissions are based on state-of-the-science gridded inventories for the observation period, including daily satellite fire count data to constrain biomass burning emissions. The derived a posteriori emissions are consistent with the observations, a priori constraints and their respective errors. We account for the model transport error using an innovative approach based on paired forecasts as well as differences between observations and forecasts. This method accounts for the daily spatial correlations of the errors. We examine the sensitivity of the a posteriori source estimates to the structure of the error covariance as well as the complementarity of the satellite and aircraft observations towards constraining the detailed structure of Asian CO sources.