Comparison of observed chemical distributions during the presence and absence of Asian transport events during ITCT 2002

Episodes of inflow to the West Coast of air clearly influenced by recent Asian emissions were sampled from the NOAA WP-3D aircraft during the ITCT project in April and May 2002. The aircraft also sampled episodes of inflow in which recent Asian emissions were not clearly apparent. These latter episodes are influenced, in part, by recirculation of air from North America and by longer-term transport over the relatively source-free Pacific Ocean. The frequency of occurrence and distributions of chemical species, with a focus on the reactive nitrogen species, for these latter episodes will be compared to distributions characteristic of more recent Asian input during the ITCT project.