基于多雷达观测和数值模拟的中天山北坡夏季降水过程研究  

A Case Study on Summer Precipitation Process in the Central Tianshan Area Using Multi-radar Observation and Model Simulation

作　　者：刘恩弘 杨璟[1] 银燕[1] 景晓琴 杨军[1] 李斌 杨玲[4] 佘勇[4] 袁亮 林彦君 姜冬昕 LIU Enhong;YANG Jing;YIN Yan;JING Xiaoqin;YANG Jun;LI Bin;YANG Ling;SHE Yong;YUAN Liang;LIN Yanjun;JIANG Dongxin(Key Laboratory for Aerosol–Cloud Precipitation of China Meteorological Administration,Nanjing University of Information Science&Technology/Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters,Nanjing 210044;Key Laboratory of Cloud and Fog Physical Environment of China Meteorological Administration,Beijing 100081;Weather Modification Office of Xinjiang Uygur Autonomous Region,Xinjiang 830002;College of Electronic Engineering of Chengdu University of Information Technology Chengdu,610225;Chengdu Plain Urban Meteorology and Environment Scientific Observation and Research Station of Sichuan Province,Chengdu 610225)

机构地区：[1]南京信息工程大学气象灾害预报预警与评估协同创新中心/中国气象局气溶胶与云降水重点开放实验室,南京210044 [2]中国气象局云雾物理环境重点开放实验室,北京100081 [3]新疆维吾尔自治区人工影响天气办公室,新疆830002 [4]成都信息工程大学电子工程学院,成都610225 [5]成都平原城市气象与环境四川省野外科学观测研究站,成都610225

出　　处：《大气科学》2023年第6期1807-1826,共20页Chinese Journal of Atmospheric Sciences

基　　金：科技部重点研发项目2017YFC1501402;西北人工影响天气工程项目ZQC-R18211;中国气象局西北区域人影建设研究试验项目RYSY201902;国家自然科学基金项目41905124;42005064;江苏省自然科学基金项目BK20190777;BK20190778。

摘　　要：基于微雨雷达、Ka波段云雷达、C波段天气雷达和微波辐射计等仪器的观测资料对2019年7月27日中天山地区一次局地对流云降水过程的精细结构及演变过程进行分析,并结合WRF高分辨率数值模式模拟结果研究了热力不稳定结构及风切变层对云发展的影响。结果表明:此次降水过程中天山北坡区域受到地形热力强迫,形成爬坡气流,并与翻越天山山脉的偏南气流在局部形成对流;雷达观测发现,由于天山山区受到高空西风的控制,局地产生的对流云团不足以突破中天山北坡上空的风速较大的西南气流或偏西气流,低层的偏北气流被高层气流夹带而转向形成风切变层。降水发生后,低层对流云团被限制在风切变层以下,云顶平整且高度较低,风切变层对对流云团存在明显的抑制作用。通过分析模拟结果,此次降水过程中风切变层对中天山北坡降水云的发展及热力不稳定变化影响十分重要,高层西南风对相当位温的平流输送使得风切变层上空更倾向于热力不稳定,同时使其下方更倾向于热力稳定从而抑制低层对流而促进高层对流的发展。当低层对流云团强度不足以突破其上空因垂直风切变导致的稳定层结,对流便会被局限于垂直风切变层以下,使得降水强度减弱。The fine vertical structure and evolution of orographic precipitation in the middle Tianshan area was analyzed using measurements taken from a micro rain radar,Ka-band cloud radar,and microwave radiometer.In addition,a highresolution simulation is conducted to analyze the thermal instability and wind shear layer influence on cloud generation.The observations reveal that the precipitation was generated owing to the convergence between the southwesterly wind flying across the mountain ridge and the northerly wind generated by the thermal forcing in the terrain.Because the observed convective updraft was not strong enough,the low-level northerly flow turned southward as it approached the high-level southwesterly wind,resulting in strong wind shear.Following the precipitation,the low-level convective clouds were constrained to remain below the wind shear layer,and the cloud tops were generally flat and low,indicating that the wind shear layer significantly inhibited the convection.The model simulation suggests that the influence of wind shear on developing precipitation clouds and the change in the thermal instability on the northern slope of the Central Tianshan Mountains during this precipitation is crucial.The advective transport of equivalent potential temperature,caused by the action of upper-level southerly winds,was responsible for the layer above the wind shear layer becoming thermally unstable and the layer underneath it becoming thermally stable,thereby suppressing low-level convection and promoting upper-level convection.If low-level convective updrafts were not strong enough to break through the stable laminar junction caused by vertical wind shear,convection would be constrained to remain below the vertical wind shear layer,preventing intense precipitation.

关 键 词：中天山 多雷达观测 风切变 位势散度 

分 类 号：P401[天文地球—大气物理学与大气环境]