Assimilation of MAPS CO in a global three - dimensional model

Observations of carbon monoxide (CO) by the MAPS instrument onboard the Space Shuttle were assimilated into a global three-dimensional chemistry transport model using the Optimal Interpolation approach. The assimilation considerably improved the calculated distribution of CO in the troposphere. On the global scale, the adjustment of the CO eld resulting from the assimilation procedure was large at the beginning of the assimilation, suggesting discrepancies in the initial conditions of the model. As the model integration/assimilation progresses with time, transport caused the model to drift. This drift limited to a few days the "memory" of CO from its adjustment towards the observations. The assimilation of CO signi cantly in uenced the distribution of other chemical species, even over the limited time periods ( 10 days) analyzed.