DEDUCING CCL3F EMISSIONS USING AN INVERSE METHOD AND CHEMICAL-TRANSPORT MODELS WITH ASSIMILATED WINDS

The ability of inverse modeling to deduce the sources of CCl3F using a chemical transport model based on assimilated winds is examined. The sources of CCl3F are relatively well known and thus offer an opportuni ty to test methodologies that can be used to estimate the source stren gths of trace gases whose sources are less well constrained. The Model of Atmospheric Transport and Chemistry (MATCH) is used in combination with assimilated winds from the European Center for Medium-Range Weat her Forecasts (ECMWF) operational analysis and National Center for Env ironmental Prediction (NCEP)/National Center for Atmospheric Research reanalysis. Using our best a priori information about the emissions, c omparisons are made between model simulations and observations at nine observing stations from the Atmospheric Lifetime Experiment/Global At mospheric Gases Experiment and the Climate Monitoring and Diagnostics Laboratory networks. The model simulates many features of pollution ev ents and seasonal variability with both wind data sets. However, the i nterhemispheric gradient is too strong in the simulations with the ECM WF winds, although it is accurate with the NCEP winds. A recursive wei ghted least squares inverse method is used to determine the magnitude of emissions from five regions. The total magnitude as well as the hem ispheric distribution of the sources of CCl3F are correctly estimated using the combination of the observations, model transport, and assume d a priori emission distribution. However, longitudinal source informa tion is more difficult to estimate from observations. A sensitivity st udy suggests that locating the observing stations closer to the source regions would improve the ability of the inverse method to deduce lon gitudinal information about the sources.