干侵入对伊犁地区“2016.08.01”暴雨过程的影响分析

Impact Analysis of the Dry Intrusion on Rainstorm on 1 August 2016 in Yili Region

摘要: 本文利用NECP/NCAR再分析资料，分析了2016年8月1日发生在伊犁地区一次暴雨过程的大尺度环流背景和水汽条件，运用相对湿度、风矢量、位势涡度、假相当位温和垂直涡度等多种物理量场，研究了该暴雨过程中干侵入的机制和特征，以及对暴雨发生、发展和维持的影响。结果表明，此次强降水过程是在南亚高压东部发展型及西太平洋副高压西伸北挺的大尺度环流背景下产生的；水汽主要来源于南边界，持续的水汽的辐合为暴雨提供了有利的水汽条件。受南支槽发展东移的影响，干侵入在垂直层次上表现为由对流层中高层向低层的侵入，水平方向上主要表现为由西向东的侵入，并存在暖湿空气和干冷空气的长期对峙；当对流层中高层具有高值位涡的干空气侵入到低层时，导致低层的垂直涡度值增加，使得低层辐合加大，上升运动加强，有利于大降水的出现。

Abstract: Using NECP/NCAR reanalysis data, the paper analyzes a large scale circulation background and the conditions of water vapor of the heavy rain process occurred on the August 1, 2016 in the Yili region, and using the relative humidity, wind velocity, potential vorticity, false quite moderate vertical vorticity and other physical quantity, research the mechanism and characteristics of the dry intrusion in the heavy rain process, as well as to the occurrence, development and maintenance of the impact of the storm. The results show that the heavy precipitation process is produced in the background of the large scale circulation of the South Asia High eastern development and the West Pacific Subtropical High of the westward and northward advance. The water vapor is mainly from the southern boundary, and the continuous water vapor provides favorable conditions for the rainstorm. Affected by development of southern trough eastward, dry intrusion in the vertical level performs an invasion of the upper to the lower troposphere, horizontal main performs an invasion of the west to the east, and has the long-term confrontation of moist air and dry cold air; when a high value vortex in the upper troposphere of dry air intrudes to low-level, leads to lower vertical vorticity value increases, making low-level convergence, the strengthening of upward movement, which is conducive to the emergence of large precipitation.