Assimilation of Measurement of Air Pollution from Space (MAPS) CO in a global three-dimensional model

Observations of carbon monoxide (CO) by the Measurement of Air Pollution fr om Space (MAPS) instrument onboard the space shuttle were assimilated into a global three-dimensional chemistry transport model using the Physical-spa ce Statistical Analysis System approach. The assimilation considerably impr oved the calculated distribution of CO in the troposphere. On the global sc ale, the adjustment of the CO field resulting from the assimilation procedu re was large at the beginning of the assimilation, suggesting discrepancies in the initial conditions of the model. As the model integration/assimilat ion progressed with time, transport: caused the model to drift. This drift limited to a few days the "memory" of CO from its adjustment toward the obs ervations. The assimilation of CO significantly influenced the distribution of other chemical species, even over the limited time periods (similar to 10 days) analyzed.