中国西部地区暴雨过程高、低空急流耦合影响机制的个例研究  

Case Study of the Coupling Mechanism of High-and Low-Level Jets of the Rainstorm Process in West China

作　　者：段海霞[1] 姚秀萍[2] 刘新伟[3] 周甘霖 赵采玲[1] DUAN Haixia;YAO Xiuping;LIU Xinwei;ZHOU Ganlin;ZHAO Cailing(Northwestern Regional Center of Numerical Weather Prediction/Key Laboratory of Arid Climate Change and Disaster Reduction of China;Meteorological Administration and Gansu Province,Institute of Arid Meteorology of China Meteorological Administration,Lanzhou 7300202 China Meteorological Administration Training Center,Beijing 100081;Lanzhou University,Lanzhou 730000)

机构地区：[1]中国气象局兰州干旱气象研究所,甘肃省干旱气候变化与减灾重点实验室/中国气象局干旱气候变化与减灾重点开放实验室,兰州730020 [2]中国气象局气象干部培训学院,北京100081 [3]兰州大学,兰州730000

出　　处：《大气科学》2023年第6期1907-1924,共18页Chinese Journal of Atmospheric Sciences

基　　金：国家自然科学基金项目U2142208、42030611;灾害性天气国家重点实验室开放项目2021LASW-B17;西北区域数值预报创新团队项目GSQXCXTD-2020-02;甘肃省自然科学基金项目21JR7RA697。

摘　　要：高、低空急流对中国暴雨有重要影响,但是其对中国西部地区暴雨影响的深入研究缺乏,其耦合过程及机制的研究更少。本文利用常规观测、加密自动气象站降水资料以及NCEP/NCAR再分析资料,借助数值模拟,研究高、低空急流耦合效应对2018年7月8~11日中国西部一次特大暴雨过程的影响及其发生机制。结果表明:(1)此次暴雨过程是在中高纬东移冷涡低槽与副高西伸北抬的有利背景下产生的,高、低空急流耦合有利于暴雨的发展。(2)高、低空急流耦合主要通过次级环流和动量下传得以实现:高空急流加强高层辐散下沉,同时低空急流加强低层辐合上升,促使高、低空急流之间形成次级环流,其下沉支引导高层高值位涡向下层传播,形成动量下传,与中层高值位涡区相衔接,高、低空急流在中层耦合。(3)高、低空急流的耦合,加强了中层不稳定能量的聚集,促使低空急流加强发展;进而增强了辐合强度,促使上升运动加强,从而增强了降水强度。通过增减高、低空风速的敏感性试验发现,高低层风速的增减能够改变中低层最大位涡的增减,其基本对应了强降水时段,且位涡值越大降水强度越强。(4)高、低空急流强度共同对降水强度有重要影响:数值模式敏感试验表明,当同时增加高低空急流强度,降水强度将增强,而仅增加高空或低空急流,降水强度变化不大,但减弱高空或低空急流强度,降水强度均会减弱。High-and low-level jets have a substantial influence on heavy rainfall events in China;however,detailed studies on their effects on heavy rainfall in arid and semiarid West China and their coupling processes and mechanisms are lacking.In this study,the effects of the coupling effect and mechanisms of high-and low-level jets on a severe rainstorm process in western China were investigated by conventional observations,encrypted automatic meteorological station,and NCEP/NCAR reanalysis data.It was revealed that(1)heavy rain is generated under the favorable background of the southwest airflow on the west side of the western Pacific subtropical high,with cold air moving to the east and westward and northward by the cold trough low trough carrying mid-high latitudes.Thus,the coupling of high-and lowlevel jets is beneficial for rainstorm development.(2)High-and low-level jets are coupled with momentum transmission through secondary circulation.First,the high-altitude strong zonal wind speed in the north side of the high-level jet strengthens the divergence of the upper layers and creates a sinking movement,and the low-level strong zonal wind speed in the northwest side of the low-altitude jet strengthens the low-level convergence,which creates an upward movement under the action of the terrain uplift.A secondary circulation is formed between the high-and low-level jet streams.The sinking air flow of the secondary circulation guides the high-level potential vortices from the high level to the low level to propagate and move downward.The down flow is connected with the high potential vorticity region in the middle layer,and the coupling channel of high-and low-level jet flow is cleared.(3)The coupling of high-and low-level jets in the middle layer strengthens the accumulation of conditional symmetric instability energy in the middle layer,which promotes the development of low-level jets.Consequently,the intensity of convergence is improved,as well as the upward movement,to enhance the precipitation intensity.After conduct

关 键 词：西部暴雨 高、低空急流耦合 数值模拟 动量下传 次级环流 

分 类 号：P442[天文地球—大气科学及气象学]