A numerical simulation of dust storms in China

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  • Environmental Modelling & Software 19 (2004) 141151www.elsevier.com/locate/envsoft

    A numerical simulation of dust storms in ChinaZhenxin Song

    The Atmospheric Science Department of Lanzhou University, Lanzhou, 730000, Peoples Republic of ChinaReceived 30 September 2002; received in revised form 20 January 2003; accepted 18 February 2003

    Abstract

    Wind erosion occurs in many arid, semiarid and agricultural areas of the world. The desert areas of China, which occupyapproximately 13% of Chinas total surface area, are major sources of Asian dust. The major wind-erosion areas are the sandylands in western and northwestern China together with the extensive regions of the Gobi desert in northern and northeastern China,especially along the basin of the Yellow River. In this paper, dust storms which occurred in China in the spring of 2002 weresimulated using an integrated numerical modeling system.

    The purpose of the simulation is to produce quantitative predictions of wind erosion on regional scales. The integrated winderosion modeling system used in this study coupled the following three major components: (1) An atmospheric prediction model,together with a land-surface model; (2) a wind-erosion model and (3) a geographic information database. The atmospheric modelprovides the necessary input data for the wind erosion scheme, including wind speed and precipitation. It also provides input datafor the land-surface model that produces predictions for soil moisture. Dust transport and deposition are also considered in theatmospheric model. The wind-erosion model predicts streamwise saltation and dust emission rate for given atmospheric, soil andland surface conditions. The geographic information database provides spatially distributed parameters, such as soil type and veg-etation coverage, for the atmospheric, land surface and wind erosion models.

    Dust storms in China occur mainly in spring and winter, but most frequently in April. In spring, surface soils frozen in theprevious winter become especially loose, creating a favorable condition for wind erosion. As an example, the severe dust stormsof 1520 March were simulated. The results show the integrated modeling system can simulate the main characteristics of the duststorms. The system produced estimates of wind erosion intensity and patterns that are in agreement with observations. Such asystem offers the possibility of determining wind erosion patterns on broad scales with high spatial resolution, as well as dusttransport and deposition. 2003 Elsevier Ltd. All rights reserved.

    Keywords: Wind erosion; Dust storm; Numerical simulation; Integrated modeling system

    1. Introduction

    Wind erosion is a serious environmental problem inarid and semi-arid regions of China and in many otherparts of the world. Strong wind erosion events, such assevere dust storms, may threaten human lives and causesubstantial economic damage. The northwestern Chinaregion is one part of the central Asia dust storm area.The desert areas of China, which occupy approximately13% of Chinas total surface areas, are major sources ofAsian dust. These areas include the temperate arid land

    Present address: National Meteorological Centre, Zhong GuancunSouth Street 46, Beijing 100081, China. Tel.: +86-10-6840-7469; fax:+86-10-6840-8584.

    E-mail address: songzhenxin@vip.sina.com (Z. Song).

    1364-8152/$ - see front matter 2003 Elsevier Ltd. All rights reserved.doi:10.1016/S1364-8152(03)00116-6

    from 75E to 125E and from 35N to 50N (Liu, 1985).The major wind erosion areas are sandy lands in westernand northwestern China together with the extensiveregions of the Gobi desert in northern and northeasternChina, especially along the basin of the Yellow River(Liu, 1985; Walker, 1982). The dust storms occurring inthe north part of China and Mongolia are called EastAsian dust weather. Recently, dust storms occurred fre-quently in the spring in China, which caused the wideattention of the public and the government. Wind erosionis an environmental process influenced by geological andclimatic variations as well as human activities. It occurswhen a soil surface is unprotected by vegetation coverand sufficiently dry, under such conditions, wind is ableto pick up sand sized particles, which bounce along thesurface and eject more particles, including dust particles.

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    Those dust particles, which usually contain most of theorganic matter and nutrients, may be carried a long dis-tance by the wind, notably as dust storm or dust hazes.It reduces soil productivity and leads to land degra-dation. Wind erosion causes loss to public utilities. Forinstance, dust suspension reduces visibility, sandblastingdestroys young crops, and dust related air pollutioncauses a health hazard, etc. Hence, the simulation andforecast of a dust storm is not only important for longterm sustainable agriculture but also has significanteconomic benefits.

    Considerable insight has been gained into the physicsof wind erosion since Bagnold published his pioneerwork The Physics of Blown Sand and Desert Dunes in1941 (Bagnold, 1941). Suspension, saltation, and creepare the three distinct modes which occur during winderosion (Bagnold, 1941). Shao (2000) treats the physicsof wind erosion rigorously from the viewpoint of fluiddynamics and soil physics. The purpose of developing awind erosion modeling system is to produce a quantitat-ive prediction of wind erosion on scales from paddockto global. The system should have the capacity of mode-ling the complete wind erosion process, from particleentrainment through transport to deposition. It is a formi-dable task because wind erosion is governed by a widerange of factors involving atmospheric conditions, soilstates and surface properities. A lot of progress on thesimulation of dust weather has made. The first attempt tocombine the information of atmospheric data with land-surface data for wind erosion assessment was made byGillette and Hanson (1989) in their investigation of thespatial and temporal variations of dust production in theUnited States. In atmospheric studies, dust emission andtransport have been under research since the late eighties(e.g. Westphal et al., 1988; Tegen and Fung, 1994,1995). However, in most of these studies, crude winderosion schemes and coarse land surface data were used,which limited the reliability of the modeling results.Marticorena and Bergametti (1995); Shao et al. (1996)and Marticorena et al. (1997) have developed betterwind erosion schemes which account for the impact ofsurface properties on sand drift and dust emission. Shaoand Leslie (1997) and Lu and Shao (2001) havedeveloped and implemented an almost fully integratedwind erosion modeling and prediction system.

    In the spring of 2002, a research group was estab-lished in CMA (Chinese MeteorologicalAdministration). Members of the group come from NMC(National Meteorological Centre), NSMC (National Sat-ellite Meteorological Centre), IAP CAS (Institute ofAtmospheric Physics, Chinese Academy of Sciences)and IGE CAS (Institute of Geography, Chinese Acad-emy of Sciences). The Group used an integrated winderosion modeling system developed by Shao and Li(1999 and Shao and Lu, 2000), land surface data andGIS data to make real time forecast of dust storms that

    occurred in China from March to May in 2002. Duringthese periods, NMC provided numerical forecasts pro-ducts on dust weather every day. It is the first real timeforecast of dust weather in China. In this paper, wereport the basic facts on dust simulation and predictionin China in the spring of 2002. At the same time themodel results are compared with observation images.

    2. An integrated wind erosion prediction system

    2.1. System structure

    The framework of an integrated wind erosion mode-ling system is as illustrated in Fig. 1. It is composed ofan atmospheric model, a land surface scheme, a winderosion scheme, a transport and deposition scheme anda geographic information database. The atmosphericmodel provides input data for other three model compo-nents. The land surface scheme simulates energy,momentum and mass exchanges between the atmos-phere, soil and vegetation, but more important in thecontext of wind erosion modeling, it produces the soilmoisture as an output. The wind erosion scheme obtainsfriction velocity from the atmospheric model, soil moist-ure from the land surface scheme and other spatially dis-tributed parameters from the GIS database. The winderosion scheme predicts streamwise saltation flux anddust emission rate for different particle-size groups. Thetransport and deposition model obtains flow velocity,turbulence data and precipitation from the atmosphericmodel and dust emission rate and particle-size infor-mation from the wind erosion scheme. Fig. 1 also illus-trates a possible computational procedure, the atmos-pheric model is first run after initialization for

    Fig. 1. The structure of integrated wind erosion modeling systemconsisting of an atmospheric prediction model, a land surface model,wind erosion model, a transport and deposition scheme and a GIS data-base.

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    atmospheric dynamics and atmospheric physics. This isfollowed by running the land surface scheme and winderosion scheme. Finally, the calculation of dust transportand deposition is carried out.

    2.2. Weather prediction model

    The atmospheric model of the integrated system is ahigh resolution limited area weather prediction modeldeveloped at The University of New South Wales byLeslie and his colleagues (Leslie and Purser, 1991),referred to as HIRES (High Resolution Limited AreaModel). It is a primitive equation model on a Lambert-Conformal projection and utilizes the s coordinate withthe Arakawa