Characterizing the transport pathways of Asian dust

Backward trajectories, synoptic analyses, and regional dust models are applied to analyze the aerosol particles obtained from aircraft measurements during major dust events in the Asian Pacific Regional Aerosol Characterization Experiment (ACE-Asia) to understand the controlling mechanism of Asian dust transport. The selected high concentrations of aerosol measurements are traced back to their source areas, and the summarized eleven representative trajectories of dust particles are categorized into three types, including the upper-level (U type), lower-level (L type), and descending (D type) transport. The characteristics of the dust transport during different stages for each of the three types are inspected. It is found that the transport distance of a dust event strongly depended on the source areas relative to the synoptic conditions. For source areas ahead of a trough, the dust particles can be uplifted into the free troposphere. If the uplifted dust particles move to the ascending areas of a trough or ascend due to other processes in the later stage, then the dust particles likely travel longer distances. When dust particles ascend in an area too close to the trough, their subsidence may be expected as sinking motion could occur after trough passage, and thus the transport distance is limited. Uplifted dust particles are typically found at a height of 400-700 hPa (2-4.5 km above ground level) over source regions. For dust particles that are generated behind a trough, the vertical motion is limited to a layer around 700 hPa, and the transport distance is also shorter.