Comparison of the Synoptic Environments Conducive to Eastward versus Southeastward Transport of Asian Dust Events

Asian dust events that travel eastward and southeastward in the lower troposphere affect different areas near the coastal East Asia. To understand the synoptic differences between the two types of dust events, four dust events from 2006 to 2009 are selected for each type and the synoptic environment is compared. Surface measurements, trajectory analyses, and a regional dust model are also applied to further analyze each type. Results show that the strength of the low-level trough and the surface anticyclonic system are important in determining the transport route of dust event. A deep 700–850 hPa trough extending far south beyond 30°N associated with an intense surface anticyclone with maximum pressure greater than 1020 hPa over coastal East Asia favors southeastward movement of dust event. The prevailing northwesterlies or northerlies behind the deep trough and ahead of the intense surface anticyclone promote the southeastward movement of dust event. Since intense surface anticyclones often associated with strong dust events, severe dust activities tend to move southeastward. In contrast, a shallow trough accompanied by a weak surface high locating north of 30°N over the coastal East Asia favors an eastward transport route.