A Global Modeling Initiative (GMI) Study of the Sensitivity of Transport to Meteorological Fields: Preliminary Results

A credible model simulation of the transport and transformation of trace gases and aerosol in the atmosphere requires a realistic representation of small (sub-grid) to large (resolved) scale meteorological phenomena. We are evaluating the credibility of circulation produced by several meteorological fields that drive transport in the Global Modeling Initiative (GMI) chemical tracer model (CTM). The GMI CTM is uniquely suited for this study as it can use meteorological input from various general circulation models (GCM) and data assimilation systems (DAS). These input include the 1) GEOS-4-DAS fields [Goddard Earth Observing System (GEOS) DAS, version 4] from the Goddard Modeling and Assimilation Office (GMAO), 2) GEOS-4 DAS forecast fields (GEOS-4-Forecast), 3) Oslo/European Centre DAS forecast fields (Oslo/EC-Forecast) from Oslo University and U. California, Irvine, and 4) GEOS-4 Atmospheric GCM fields (GEOS-4-AGCM). We are assessing the model's simulation of large-scale circulation, such as stratosphere-troposphere exchange (STE) and tropospheric inter-hemispheric exchange (IHE), as well as smaller scale motions, including convection and pollution plume transport. It is known that DAS fields can cause unrealistic transport, such as excessive STE, in a CTM due to the non-physical forcing introduced by data insertion. The use of forecast fields should partially damp the physical effects of data insertion, producing more realistic transport while maintaining information from the assimilation procedure.