Model Study on the Transport and Mixing of Dust Aerosols and Pollutants during an Asian Dust Storm in March 2002


The transport and mixing of dust aerosols and pollutants in East Asia during March 18 to 22, 2002 was studied using the nested air quality prediction model system (NAQPMS). Dust was primarily generated in the Gobi desert on 19 March and then swept across several areas of East Asia. The model results were verified with observations of surface weather, TSP/PM10, SO2 and lidar data. The model simulated the right timing and strength of dust events, capturing most of the variation features in dust and SO2. Numerical results showed that the dust aerosols were mainly transported in two layers and mixed with pollutants in different ways. Some of the dust kicked up in the source region was uplifted to a higher layer (200 - 2000 m layer) and transported downwind faster than dust of the lower level. This lower-level dust was of greater concentration. The dust arriving at the upper layer began to drop and mixed well with pollutants in the atmosphere during "the first period". During "the second period", pollutants were diluted by the dust air mass that was transported along the lower layer. The remaining pollutants mixed well with dust aerosols during this period. The mixed air mass of the higher layer (1500 m) eventually reached the Northwestern Pacific. A large amount of clouds in the upper layers potentially led to an increase in sulfate mass on the surface of dust particles.

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