Numerical Studies on a Severe Dust Storm in East Asia Using WRF-Chem

Abstract

Dust storm is one of the important natural disasters, which can have significant impact on terrestrial ecosystem, global climate, air quality and human health. In Mar. 19-23, 2010, a serious dust storm occurred over East Asia. It started from Mongolia, initially extending to the east, turning to the South of China, then back to the Northeast Asia. About 20% of the areas in China suffered from this severe dust event and the air was heavily polluted with massive airborne particulates. The Air Pollution Index (API) in many cities exceeded 500 when dust storm passed by, while the maximum surface PM10 concentration reached 1900 &#181g/m3 in east area. The coarse particles were dominated in PM10, with fine particles named as PM2.5 only accounting for 5% - 20% at cities along the dust moving track in South and East China. MODIS and CALIPSO satellite data were used to investigate the horizontal and vertical patterns of optical parameters of dust aerosol. The average AOD reached 2 - 2.5 on dust days in most southeast regions. The dust can be transported up to 5 Km with maximum aerosol extinction coefficient of 0.35 - 0.4 at 1 - 3 Km in vertical. Synoptic weather was analyzed to understand the meteorological conditions and the backward trajectories were calculated to investigate the movements of air mass. The WRF-Chem model (Version 3.2) was applied to simulate the transport and deposition of the dust aerosols. The performance of Shaw (2008) and Chin (2002) parameterization schemes for dust emissions in WRF-Chem were evaluated. Modeling results were compared with the CUACE-Dust and RegCCMS. Investigations show that WRF-Chem has capability on simulations on dust emission, long range transport and deposition. Shaw (2008) scheme gives more reasonable spatial distribution of dust aerosols, while Chin (2002) scheme presents more better results in terms of PM10 surface concentration simulation. It is suggested that two schemes can be used at the same time in terms of simulation of dust pattern and concentration.