The long-range transport of Asian air pollution: Its variability and impacts on western North America

This dissertation uses measurements from the Mt. Bachelor Observatory (MBO: 43.98° N, 121.69° W; 2.7 km above sea level) in the Cascade Range of central Oregon and elsewhere to investigate the impacts and causes of variability in the Asian long-range transport of air pollution (ALRT) on multiple spatiotemporal scales.;Carbon monoxide (CO) observations from MBO, satellite retrievals, a global chemical transport model (CTM) and a backtrajectory index revealed that significant declines (2-21%) in springtime CO at MBO and elsewhere from spring 2005 to spring 2006 were attributable to: (a) strong wildfires in SE Asia during winter 2004 through spring 2005, and (b) the transport pattern in March and April 2006 which limited the inflow of East Asian industrial pollution to the lower free troposphere (FT) over western North America (NA).;Ozone (O3) results from 16 CTMs were compared to Clean Air Status and Trends Network (CASTNet) observations in the U.S. for 2001. While the impact of foreign emissions on surface O3 in the U.S. is not negligible (decline of 0.3-0.9 ppbv for a 20% reduction in anthropogenic emissions abroad) - and is of increasing concern given the recent growth in Asian emissions - the effect of NA emissions reductions (decline of 5-6 ppbv for a 20% reduction in anthropogenic O3 precursors) was found to be substantially greater.;Chairlift sounding data from MBO revealed that a boundary layer influence at the summit begins ∼10:00 PDT during spring. Using these data, I isolated FT nitrogen oxide (NOX = NO + NO2) observations from 1 autumn and 3 spring campaigns. Significant interannual variability was detected and attributed to changes in FT synoptic conditions. Substantially lower NO X levels were observed during spring 2009 when there were: (1) higher geopotential heights (Z) and warmer temperatures ( T) over the Gulf of Alaska and (2) much weaker winds throughout the North Pacific.;A characterization of the top 20 FT NOX events revealed that half (n=10) were "Imported" events with anomalously: (1) high Z off the west coast of NA, (2) warm T throughout the eastern Pacific, and (3) strong SW winds in the Asian outflow region. Five events exhibited an influence from the NA continent and were characterized by very strong cyclonic behavior off the NW U.S. coast.