P38  Tracers for CO and Ozone in WRF-Chem -  Interpretation of Pollution Sources and Chemical and Transport Processes

Pfister, G., S. Walters, D. Edwards, L. Emmons, National Center for Atmospheric Research, Atmospheric Chemistry Division, Boulder, CO

Interpretation of pollution concentrations is a complex problem due to the interplay of sources, transport and chemical processes. Including synthetic tracers can provide essential information about the contributions and relevance of different processes. In this presentation we will bring results from studies using tracers for carbon monoxide (CO) and ozone (O3) in WRF-Chem. These tracers undergo the same transport and chemistry as the standard species in the model, but estimate the concentrations from a selected source, such as a local pollution source or the inflow at the lateral boundaries, to total concentrations. The tracers are additive in that the sum of all tagged emission sources equals the total species. The CO and O3 WRF-Chem tracers are used to estimate the relative importance of local sources, regional and long-range transport as well as chemical processes to surface levels of CO and O3 over the summertime US. Special attention is also given to the role of pollution inflow to surface ozone in California during the ARCTAS-CARB field mission. The average contribution of pollution inflow on surface afternoon ozone over California is estimated as 10±9 ppbV with a larger spatial but also temporal variability.