地形对沙尘暴的影响及敏感试验研究

在初步探讨地形影响沙尘扬升、传输、沉降等动力过程可能机制的基础上,利用沙尘数值预报模式对一次强沙尘暴过程进行了模拟研究,结果表明:沙尘暴形成阶段沙尘主要来源于阿尔泰—萨彦岭及以东地区,这部分沙尘主要向东扩展,该区域地形对其强度具有重要影响;内蒙古中西部、甘肃、宁夏等地的起沙主要在沙尘暴持续阶段产生影响,之后主要向南输送,青藏高原东侧地形绕流对其强度具有影响。地形影响可以使沙尘的扩展分为两种不同的方式,当上下游地形落差较小时形成整体推进式传输,此时沙尘位于对流层低层,没有上下沙尘层的分离;当上下游地形落差较大时形成分离式传输,沙尘位于对流层中层且在传输过程中沉降很弱,同时与地面附近的沙尘层分离。源于蒙古国、内蒙古等地的沙尘往往产生整体推进式传输;而产生于青藏高原的沙尘常形成分离式传输。

The Influence of Topography on Dust Storm and Numerical Simulation

Based on the relation between the topography and dust storm and numerical simulation of a dust storm process,a primary analysis of the influence of topography on dust storm was conducted.The results shown that in the early stage of this process the dust particle mainly came from the areas around Altai-Sayan Mountain and Mongolia.The topography conducted serious influence on the intensity of dust storm.It extended eastward dominantly leaded by the cyclonic cold front.In succession,the dust particle coming from central and western of Inner Mongolia conduced a more serious influence on dust storm.It mainly extended southward leaded by the terrain-forcing rolling stream of Qinghai-Xizang Plateau.Meanwhile,the influence of topography on dust storm induced the dust transportation acted as two different manners.The dust particle raised at eastern Qinghai-Xizang Plateau was transported in the middle troposphere and as a so called Spanning manner.It means the dust particle completed the long distance transportation with little subsiding on its path and a separation of dust layers appeared.On the contrary,the dust storm formed at Mongolia and Inner Mongolia extended in the lowed troposphere down to surface and as a so called TotalPushing manner.It means the dust layers were separated two different layers in its transporting process.One is in the middle troposphere and the other near the surface.