巴丹吉林沙漠湖泊-沙山近地表风沙动力环境

Dynamical environments of wind-blown sand near lakes surrounded by sand-mountains in the Badain Jaran Desert

高大沙山与湖泊交错发育的地貌景观多年来引起了学术界的广泛关注。基于巴丹吉林沙漠腹地大沙枣海子及其周边5个气象站点的同步风况资料,探讨了区域起沙风况、输沙势以及主导输沙风向的空间分布特征。并结合湖泊-沙山独特的地貌格局,初步揭示了大沙枣海子局地环流以及风沙动力环境。由于受高大沙山的影响,大沙枣海子及其外围局地环流非常明显,合成输沙方向自湖泊中心向外围呈反向发散分布。从沙山外围至湖泊中心,起沙风次数呈同心圆状递减。合成输沙势RDP和合成输沙方向空间变化较大,湖泊西侧合成输沙方向以东南向为主,而东侧以西南向为主,区域风能属于低能环境。

Sand Mountains always accompany with lakes in some desert. Many beautiful lakes distribute in the hinterland of the Badain Jaran Desert of China. The height of Sand Mountain is about 500 m and the area of some lakes is in excess of 1 km2. Why lakes in desert are not buried by dune has attracted many scientists over world for centu- ries. The area of lakes is controlled not only by underground water but by environments of wind-blown sand between sand dunes and lakes. Specific heat, coefficient of thermal conductivity and reflectance ratio on the surface of lakes and sand mountains is different, which will change air temperature, vary field of press and then arise local circula- tion. Otherwise, timely alternative of the direction of sand-laden wind determines the balance of sand transport and affects the existence of lakes. This paper aims to reveal the effect of local circulation on sand transport between Sand Mountains and lakes. Based on the detailed wind data in the Dashazao Lake of the Badain Jaran Desert, sand-laden wind, drift potential and sand transport were investigated. Combined with the landscape of sand mountains and lakes, local circulation and dynamical environments in the Dashazao Lakes were illustrated. Drift potential around sand mountains is different and ranges from 25~58 VU to 45.01 VU, which belongs to a low-energy wind environ- ment in this region. Frequency of sand-laden wind decreases from the periphery of sand dune to the lake＇ s centre. Resultant sand-drifting direction is SE in the western side of the Dashazao Lake, and SW in its eastern side. The di- rection of sand-landed wind in the center of lake is relative unidirectional and the resultant direction is SE. Local circulation is very obvious because of the pattern of sand mountains and lakes. Average wind speed in the center of the lake is little less than that around sand mountains. The eastern sand dune threatens the lakes less than the west- ern side. A northeast-trend complex sand mountain just locates in the west side of the Dashazao Lake, and western wind passing the mountain would be decreased near the lake. Therefore, sand mountains will shelter the lakes be- cause the lakes mostly locate in the lee of the mountains. The results of this paper are important for forecast of the trends of wind-blown sand environments near lakes surrounded by sand-mountains and for attempt to show regional ecological change in the hinterland of the Badain Jaran Desert.