Model study on particle size segregation and deposition during Asian dust events in March 2002

Abstract

[1] A size-segregated aerosol model that includes most of the major physical processes (generation, transport, and dry and wet deposition) is developed. This model is coupled with a Regional Air Quality Model (RAQM) and is applied to simulate Asian dust storms during the 10-day period of 15-24 March 2002. A nonhydrostatic mesoscale model (MM5) is used to provide meteorological fields. Model results are verified by available observational data including surface weather observations and size-segregated particle concentrations. The validation demonstrates a good capability of this model system in capturing most of the key features of dust evolution and reproducing the particle mass size distribution along the transport pathway of soil dust. An apparent feature has been both observed and reproduced by the model, showing a shift of size range with peak mass concentration from coarse mode to finer mode on the pathway from source regions to distant downwind areas. The maximum dust concentration averaged over 10 days is simulated to be 3000 mg m À3 over the southern China-Mongolia border. Total dry deposition of soil dust for 10 days is up to 30 g m À2 in the Gobi desert along the southern China-Mongolia border. Distribution and magnitude of particle deposition are strongly dependent on both concentration and size-segregated dry deposition velocity and scavenging rate. While dry deposition dominates the removal of dust particles in or in the vicinity of source regions, the influence of wet deposition increases along the transport pathway of soil dust, with high removal efficiency for coarser particles (>2 mm) and very low efficiency for particles in the accumulation mode. Of the total dust emission (43.2 megatons), about 71% is redeposited onto the underlying surface by the dry deposition process, 6% is removed by the wet deposition process, and the remaining 23% is suspended in the atmosphere or subject to long-range transport.

Retrieval of Asian Dust Amount over Land using ADEOS-II/GLI near UV Data

“…(4) are approximately (2/3), since a liquid water density is about 1.0 g cm 3 and the extinction efficiency asymptotically becomes a constant 2.0. In case of Kosa aerosol, is 2.6 g cm 3 (Han et al 2004) since its main component is considered as quartz. The extinction efficiency still has a fluctuation around size parameter 30, but we assume Qext as a representative value 2.5 for simplicity in this study.…”

Asian Dust Transport to Kanto by Flow around Japan's Central Mountains

“…We briefly examine the following three possible causes of the delayed dust transport in Kanto: (1) prevention of the downward transport of dust particles by a stably stratified layer (e.g., Tsunematsu et al 2009), (2) wet deposition (e.g., Han et al 2004), and (3) indirect transport around the central mountains (this study).…”

“…1a). Wet deposition processes play an important role in dust scavenging in a downstream region (e.g., Han et al 2004). …”

Characterization of Atmospheric Organic and Elemental Carbon of PM2.5 in a Typical Semi-Arid Area of Northeastern China

“…Long-range transport of Asian dust is one of the important sources of atmospheric aerosols in the downwind regions, particularly during the dust seasons. Asian dusts can influence ecosystems, environments, and climates (Sokolik and Toon, 1996;Sokolik et al, 2001;Han et al, 2004;Cao et al, 2005;Huang et al, 2006bHuang et al, , 2008. Some Asian dust may settle on the ocean's surface and provide nutrients (e.g., Fe 2+ ) to the oceanic biosphere (Zhuang et al, 1992).…”