地形影响沙尘传输的观测和模拟研究

An observational and numerical study on the topography influence on the dust transportation

中文关键词:  沙尘暴，地形，数值模拟

英文关键词:Dust storm, Topography, Observational and numerical study

中文摘要:

      文中基于观测资料和数值模拟方法，研究了东亚地形对中国沙尘传输的影响，结果表明：东亚地区沙尘天气多发区主要位于中国南疆盆地和内蒙古西部及蒙古南部。南疆盆地沙尘天气集中在盆地南缘；而蒙古、内蒙古西部沙尘天气主要出现在沙漠腹地。青藏高原东北侧到黄土高原中部是沙尘天气次多发区。蒙古、内蒙古西部沙漠腹地多发区的形成不仅由于这里提供了丰富的沙源，同时也具备了沙尘暴迅速增强的条件：阿尔泰-萨彦岭南侧的峡谷地形强迫形成峡谷急流，明显增强了该区域地面风速；萨彦龄山地南坡携带大量沙尘的向南下坡气流遇到东—西向的峡谷气流时受到阻挡形成聚集；同时，这一地区起伏的地表产生的地形波加强了地面起沙。这种大量沙尘在大气中聚集之后再进行传输的特征可以视为在大气中形成了沙尘“中继站”。导致沙尘进一步向东输送的地形因素是阿尔泰—萨彦岭山地南侧的峡谷地形，而萨彦岭山地南坡的下坡气流和青藏高原东北侧的地形强迫绕流是导致沙尘向南输送的原因。由于青藏高原地形绕流的强大以及冷锋过程的相对频繁使得沙尘的向南输送更为强盛，这也是青藏高原东北侧沙尘天气多发区的形成原因。

英文摘要:

      Through the observational statistic analysis and numerical simulation, a study on the influence of topography in eastern Asia on the dust transportation was conducted. The results showed that the high frequency dusty weather regions locate at the west of Inner Mongolia and southwestern Mongolia, especially at the hinterland of deserts, and also locate at the southern Xinjiang basin, especially at the south of it. The second high frequency dusty weather region is on the northeast of Qinghai Tibet plateau. The dusty weather more frequently occurred at western Inner Mongolia and southwestern Mongolia is owing to some factors favorable for the dust storm formation besides plenty of dust particles can be provided there. Firstly, the canyon jet, which forms at south of Altai Sayan mountain, enhanced the surface wind speed and so in favor of the buildup of dust storm. Secondly, the southwardly downslope stream carrying a mass of dust particles from Sayan mountain was obstructed by the eastwardly canyon jet and so the dust particles concentrate there and dust storm boosts up. Thirdly, most mountains and hilly lands exist there, which produce the topographical wave and boost up the dust rising. The pattern that dust particles assemble in the atmosphere (form a severe dust storm) before they transport can be say a “dust relay station" forming there.The topography also affects the spreading of dust storm. The eastwardly canyon jet enhances the eastwardly transportation of dust particles from the “dust relay station". The downslope stream from the Sayan mountain and the topography forcing circum stream at the northeast of the Qinghai Tibet plateau enhances the southwardly transportation of dust partcles. Owing to the circum stream is so strong and the occurrence of cold front is so frequent, which transport the dust particles southwardly too, that the dust transportation in northern China is most