A high-resolution numerical study of the Asian dust storms of April 2001 : Characterization of Asian aerosols and their radiative impacts on climate

A comprehensive dust aerosol model is developed and fully coupled to the U. S. Navy's operational Coupled Ocean/Atmospheric Mesoscale Prediction System (COAMPS). The model is used to simulate the Asian dust storms of 5-15 April 2001 at 27-km resolution with 46 vertical layers. Dust was primarily generated in the Gobi and Taklamakan Deserts between 6 and 9 April and then swept across vast areas of east Asia. The model performance is verified with satellite products and by observations of PM10 and lidar data from Lanzhou, Beijing, Hefei, Tsukuba, and Nagasaki. The model simulates the right timing and strength of dust events, predicting depths and magnitudes of the boundary layer and elevated layer of dust plumes that compare well with observed values. Numerical analysis shows that the first Mongolia cyclone on the 6 and 7 April and the cold front on 8 and 9 April, accompanied by a second Mongolia low, form the major dynamic forcing patterns that mobilize, transport, and vertically redistribute the dust. Both cyclones entrain the dust and transport dust to altitudes of 8-9 km, while at the top of the cyclone, transport is anticyclonic and to the northeast. The analysis of the individual dynamic and microphysical tendency terms in the mass continuity equation reveals that in the dust generation area, mechanical and convective turbulence plays the major role in mixing dust upward to the top of the planetary boundary layer. In the downstream cyclone area, vertical advection by the model-resolved upward motion in the cyclones is the dominant dynamic process that transports dust to high altitudes and into the westerlies, making it available for long-range transport. The mass budget calculation for the entire simulation period reveals that about 75% of the total dust production is redeposited to the Asian deserts, 20% falls onto nondesert areas through dry and wet deposition, and 1.6% falls into the China and Japan Seas.