Analysis on the Influence of Topography on a Short-Time Local Heavy Rainfall Forecast in Western Xinjiang

Abstract

Based on the prediction results of RmAPs-CAV1.0, a short time heavy rainfall in western Xinjiang was simulated and analyzed. By comparing the forecast results with the actual precipitation, it is found that RMAPS-CAV1.0 can accurately reflect the important forecast parameters of the short-time heavy precipitation system, such as precipitation level and starting time. Contrast observation and prediction results found that the terrain has forced effect to the surface wind field, the precipitation process in Yili valley special opening of the west mountain terrain, the center is located in Kazakhstan in central Asia low vortex cause lower for the westerly Yili river valley, the center is located in the Tarim Basin of central Asia for Piandongfeng middle low vortex makes the Yili river valley, cause the Yili river valley and the lower levels of vertical wind shear reinforcement; In the Yili River Valley, the combination of topography and the central Asian vortex circulation in Kazakhstan forms a low-altitude convergence line. The low-level westerly winds transport water vapor into the valley, and the northerly airflow in the valley and the northern margin of the Taklamakan Desert converge near the windward slope, and the enhanced upward movement results in the uplift of the water vapor accumulated in the valley. The result analysis of RMAPS-CAV1.0 shows that the warm and cold airflow and water vapor under the action of topography have important contributions to the generation of this precipitation.