Interpretation of Ground-based and Airborne Observations of Long-Range Transport in the Pacific Northwest During Spring 2002 Using the GEOS-CHEM Global Chemical Transport Model

Observations of CO and ozone were obtained at a ground site on the western tip of Washington State (Cheeka Peak Observatory, 48.3°N; 124.6°W) from March 11 to May 31 2002. These observations were complemented by thirteen flights providing profiles of CO and ozone up to 6 km altitude. Both ground-based and airborne measurements were part of PHOBEA-II (Photochemical Ozone Budget of the Eastern North Pacific Atmosphere-II) taking place at the same time as the NOAA ITCT (Intercontinental Transport and Chemical Transformations) 2002 mission. Here we will interpret these observations using the GEOS-CHEM global chemical transport model driven by assimilated meteorology corresponding to the time of observations. Our analysis will focus on four elements: (1) validating the GEOS-CHEM model through detailed comparisons with the PHOBEA-II observations; (2) examining the origin of CO and ozone in the Northeastern Pacific by using 'tagged' tracers of source regions; (3) investigating rapid long-range transport events of Asian and European emissions identified by the model; (4) placing spring 2002 in the context of ground-based and airborne observations obtained during PHOBEA and PHOBEA-II over four previous years (1997, 1998, 2000, 2001).