阿克苏地区早春一次极端降水水汽特征分析

Analysis of Water Vapor Characteristics of an Extreme Precipitation in Aksu Area in Early Spring of 2022

利用常规观测、区域自动站、地基GPS观测的大气可降水量和美国国家环境预报中心(NCEP)再分析等资料,采用水汽通量诊断、后向轨迹模型等方法,分析2022年3月18—22日(简称“03·20”过程)阿克苏地区西部极端降水的环流形势、高低空配置、水汽输送、水汽收支及水汽追踪等。结果表明:(1)此次极端降水过程因受中纬度较强西风锋区上波动影响,强降水期间,环流配置与夏季南疆西部典型暴雨过程类似,暴雨落雨处在200 hPa西南急流、500 hPa偏西气流、850 h Pa南疆盆地偏东急流、低层切变与辐合的重合区。(2)暴雨期间,水汽自南欧—地中海—里海南部—咸海南部输送至南疆西部,并在阿克苏地区北部辐合,最强水汽辐合集中在700~850h Pa;西边界各层均以水汽输入为主,水汽输入贡献占85%,水汽追踪表明低层还有来自偏东路径的水汽输送。(3)降水2 d前阿克苏站和库车站大气可降水量(PWV)出现增加,当PWV≥17 mm时,产生暴雨的可能性增大。

Based on the data of conventional observation,regional automatic station,the atmospheric precipitable water vapor observed by ground-based GPS and National Environmental Forecasting Center(NCEP)reanalysis,the circulation situation,high and low altitude configuration,water vapor transport,water vapor budget and water vapor tracking of extreme precipitation in the western Aksu region from March 18 to 22,2022(referred to as“03·20”process)were analyzed by using the methods of water vapor flux diagnosis and backward trajectory model.The conclusions are as follows:(1)The extreme precipitation process was affected by the fluctuation of the strong westerly wind front area in the mid-latitude.During the heavy precipitation,the circulation configuration was similar to the typical rainstorm process in the western part of southern Xinjiang in summer,that is,the southwest jet at 200h Pa,the west flow at 500 hPa,the east jet at 850 hPa,and the low level wind shear and convergence.(2)During the rainstorm,the water vapor was transported from southern Europe,Mediterranean Sea,southern Caspian Sea and southern Aral Sea to the western part of southern Xinjiang,and converged in the northern part of Aksu area.The strongest water vapor convergence was between 700 hPa and 850h Pa.Water vapor input is the main input in each layer of the western boundary,accounting for 85%,and there is water vapor transport from the easterly path in the upper and lower layers of water vapor tracking.(3)Two days before the precipitation,the atmospheric precipitable water vapor(PWV)at Aksu station and Kuche station showed a wetting process.When PWV was≥17 mm,the possibility of heavy rain increased.