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.