Modeled size‐segregated wet and dry deposition budgets of soil dust aerosol during ACE‐Asia 2001: Implications for trans‐Pacific transport

Abstract

Size‐segregated budgets of soil dust aerosols in Asia for spring 2001 during ACE‐Asia were investigated using the NARCM model [Gong et al., 2003b]. Simulated mass size distributions of dust deposition showed a similar size distribution to the dust emission fluxes over the source regions and a decreased peak corresponding to a 1–3 μm diameter range over downwind regions. The simulations suggest that dry deposition was a dominant dust removal process near the source areas and the removal of dust particles by precipitation was the major process over the trans‐Pacific transport pathway, where wet deposition exceeded dry deposition by up to a factor of 10. The Asian dust deposition from the atmosphere to the North Pacific Ocean was correlated not only with precipitation over the North Pacific but also with the dust transport patterns. Variations of monthly Asian dust outflow were identified with the latitudinal center of transport at 38°N in March, 42°N in April, and 47°N in May. The monthly trans‐Pacific transport patterns of Asian dust in spring were characterized. The transport axis extended around 30°N and 40°N from the east Asian subcontinent to the North Pacific in March. A zonal transport pathway around 40°N was well developed in April over the North Pacific and reached North America. However, the transport in May was separated into two pathways: an eastward zonal path over the North Pacific and a meridional path from the source regions to the northeast Asian continent. On the basis of the averaged dust budgets during spring 2001, it was found that the major sources of Asian dust were located in the desert regions in China and Mongolia with an estimated dust emission of 21.5 tons km−2, and the regions from the Loess Plateau to the North Pacific were sinks of soil dust aerosols with the Loess Plateau as the main sink for Asian dust.