Interhemispheric Transport: Mechanistic Studies for Understanding and Improving 3-D Chemical Models

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Abstract ATM-9401216 Hartley, Dana Georgia Tech Title: Interhemispheric Transport: Mechanistic Studies for Understanding and Improving 3-D Chemical Models The primary goal of the proposal research is to obtain an improved understanding of what mechanisms control the exchange of air parcels between hemispheres: This information will be used to improve 3-D chemical transport models that presently do not adequately simulate interhemispheric exchange. For some models this will involve explicitly assessing and improving the model dynamics. However, for transport models that use predetermined wind fields a parameterization of the processes involved will be necessary. In order to achieve these goals, a combination of analyses of both observations and general circulation model outputs will be employed to study the dominant locations, seasonality, and interannual variability of cross-equatorial transport. Studies will also be performed to diagnose the dynamical processes related to the exchanged of mass between hemispheres. The specific steps to meet these goals include analyzing previously completed simulations of CFCl3 transport in the Community Climate Model 2 (CCM2) forced with climatological sea surface temperatures (SSTs) to determine the location and seasonality of the transport between hemispheres. The PI will also perform runs of the CCM2, with CFCl3 as the tracer, using observed SSTs to examine the influence of the El Nino/South Oscillation (ENSO) on interannual variability of interhemispheric exchange. After the parameterzation has been tested, it will be available for general use in chemical transport models.