2017年长江中下游地区一次持续性异常降水过程分析

Analysis of one Persistent Abnormal Precipitation Process over the Middle-Lower Reaches of the Yangtze River in 2017

持续性异常降水会引起严重的洪涝灾害,造成巨大的社会经济损失。针对2017年夏季长江中下游地区持续性异常降水过程,利用2017年6-7月欧洲中心逐日再分析资料和国家气象信息中心提供的测站逐日降水资料,采用要素空间分布演变分析方法,对2017年6月22日至7月1日降水过程的时空特征和大尺度背景场进行了探讨分析。结果表明:此次持续性异常降水在长江中下游地区沿长江呈西南—东北向带状分布,具有持续性时间长、降水量大的特点;主要影响系统为西太平洋副热带高压(简称副高)、东北低压和南亚高压,其中副高的影响最大,南亚高压主要影响此次降水的范围;东北低压与副高相配合,使南下的干冷气团与北上的暖湿气团在长江中下游地区交汇,交汇位置的移动影响雨带的位置;长江中下游地区位于高空急流入口区右侧,上升运动强烈,850 hPa上的低空急流将西太平洋和印度洋的暖湿空气输送到长江中下游地区。故此次持续性异常降水是由各种因素相互配合形成的。

The occurrence of persistent abnormal precipitation will cause serious flood disasters,which will bring huge social and economic losses.In view of the persistent anomalous precipitation process in the middle-lower reaches of the Yangtze River in the summer of 2017,using daily rain gauge observations at stations provided by the National Meteoro-logical Information Center of China and ERA interim reanalysis data,from various angles(eg:the circulation situation,water vapor flux and relative humidity),the spatial and temporal characteristics and the large-scale background field re-lated to this precipitation process from June 22 to July 1,2017 were discussed and analyzed by using the method of factor spatial evolution analysis.The result shows that the persistent anomalous precipitation is zonally distributed along the Yangtze River in the southwest-northeast.It has a long duration and a large precipitation.The main impact system is the Western Pacific Subtropical High(referred to as the Subtropical High),the Northeast Low and the South Asian High,of which the subtropical high has the greatest impact,and the South Asian high pressure mainly affects the scope of the precipitation.The northeast low pressure cooperates with the subtropical high to make the dry cold air mass in the south and the warm and humid air mass in the north meet in the middle and lower reaches of the Yangtze River.At the same time,the movement of the two air mass intersections affects the position of the rain belt.The middle and lower reaches of the Yangtze River are located on the right side of the entrance area of the upper jet stream,with a strong upward move-ment.The lower jet stream on 850 hPa continuously transports warm and moist air from the western Pacific Ocean and the Indian Ocean to the middle and lower reaches of the Yangtze River.This shows that this persistent abnormal precipi-tation is formed by various factors.