Uplifting of Asian Continental Pollution Plumes from the Boundary Layer to the Free Atmosphere over the Northwestern Pacific Rim in Spring

Understanding of the uplifting of Asian pollution plumes into the free atmosphere is key to evaluating the impact of trans-Pacific transport on hemisphere-scale chemical compositions. In this study, a regional chemical transport model combined with lidar and surface observations off the northwestern Pacific Rim was used to investigate the uplifting mechanisms of Asian pollutants in the spring of 2011. The potential source regions of anthropogenic fine particulates in the boundary layer and free atmosphere in western Japan were also indentified. The model reproduced accurately the observed surface anthropogenic PM2.5 with correlation coefficient ranging from 0.5-0.65 and its vertical profiles in East Asia. Long-range transport from the Asian continent was responsible for the high anthropogenic PM2.5 concentrations in the free atmosphere over northwestern Pacific Rim in spring, with a contribution of 55-70% in selected five cases. The rarely-reported local weak trough and the saddle field over northeastern Asia were found to be important uplifting mechanisms from the boundary layer to the free atmosphere in addition to the well-known warm conveyor belt mechanism (WCB). It is suggested that more studies on these two mechanisms are needed.