南疆西部暴雨过程的动力热力结构分析

摘要/Abstract

摘要： 利用常规气象观测资料和ECMWF提供的ERA-Interim 0.125°×0.125°再分析资料，通过对2012年5月21~23日和2013年5月26~29日南疆西部两次暴雨过程中等熵面特征的对比分析，得到暴雨过程中的动力热力结构模型。结果表明：南疆西部暴雨过程是在中亚低涡系统影响下，高、中、低空急流耦合并叠加地形强迫的综合作用下形成的。中亚低涡前部中高层向东输送的冷空气翻山后下沉，与低层南疆盆地东部向西输送的冷空气汇合抬升，与中层暖空气交汇，同时上升运动加强促使水汽辐合凝结，是降水的重要原因，短时强降水时冷空气强度弱于暖空气，持续性降水时反之。中低层等熵面位涡与降水关系密切。

关键词: 暴雨, 中亚低涡, 等熵位涡(IPV), 热力动力模型, 南疆西部

Abstract: Using the conventional meteorological observation data and ECMWF ERA-Interim data (0.125°×0.125°),the isentropic surface characteristic of two rainstorms,which were occurred in the west of south Xinjiang on May 21 to May 23,2012 and on May 26 to May 29,2013 respectively,were analyzed to establish the thermal dynamic model of the rainstorm process.The results indicated that the rainstorm came from a synthetic action of topographic forcing and jet streaming coupling among high,medium and low level jet streams when there was a Central Asian low vortex.At the high level of troposphere,the South Asia High appeared in a zonal distribution with its west part being northward raised obviously and its subtropical trough being extended southward to central Asia.Therefore a strong high-altitude southwest jet stream was formed over the west of south Xinjiang which intensified the chimney effect and caused a strong divergence formed at high altitude over the precipitation region.The cold east-deflected jet at the low level was also spread into the precipitation region which caused an intense convergence.This region has the terrain with high altitudes in its west side and low altitudes in its east side,westward airflow is lifted.The overlay of the dynamic effects from both high level and low level pushed strongly the ascending motion which provided the force condition for the rainstorm. The south-deflected airflow at middle level and the east-deflected airflow at low level carried abundant water vapor into the precipitation area which produced the vapor condition for the rainstorm.The cold air in the front of the Central Asian Vortex,which has high values of vortex,climbed over the west Tianshan adding more water vapor content at the middle level over the precipitation area.Part of the cold air slid along the geographic surface and joined the cold air at the low level and this convergence pushed the ascending motion further.The lifted cold air encountered the warm air at the middle level which made the water vapor coagulate into rain.There was a significant correlation between the potential vorticity of the isentropic surface and the heavy rainfall.The isentropic potential vorticity was increased when the precipitation began,and it was decreased when precipitation was over.Rainfall was triggered by the convergence of cold air and worm air.The intensity of the cold air was weaker than that of the warm air when there was a short-time strong rainfall,and it was the other way around when there was a persistent precipitation.

Key words: rainstorm, Central Asian Vortex, isentropic potential vorticity, thermal dynamic model, west of south Xinjiang

中图分类号:

P458.121.1

李如琦, 李建刚, 王江, 孙鸣婧, 赵克明. 南疆西部暴雨过程的动力热力结构分析[J]. 干旱区地理, 2018, 41(1): 9-16.

Li Ru-qi, Li Jian-gang, Wang Jiang, Sun Ming-jing, Zhao Ke-ming. Dynamic and thermal structure characteristics of the rainstorms in the west of south Xinjiang[J]. 干旱区地理, 2018, 41(1): 9-16.

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