Response of a westerly-trough rainfall episode to multi-scale topographic control in southwestern China  

作　　者：Wei Luo Hanyue Yin Shuai Yang Yushu Zhou Lingkun Ran Baofeng Jiao Ziyang Lai 

机构地区：[1]CHN Energy Dadu River Big Data Services Co.,LTD,Chengdu,China [2]Laboratory of Cloud-Precipitation Physics and Severe Storms(LACS),Institute of Atmospheric Physics,Chinese Academy of Sciences,Beijing,China

出　　处：《Atmospheric and Oceanic Science Letters》2022年第3期37-45,共9页大气和海洋科学快报（英文版）

基　　金：supported by the National Key Research and Development Program on the Monitoring,Early Warning and Prevention of Major Natural Disasters[grant number 2018YFC1507104];the National Natural Science Foundation of China[grant numbers 41875079,41875056,and 41975137];a Key Technology Research project on multi-source meteorological data fusion in medium and small basins[grant number DSJ-KY-2021-004].

摘　　要：This study aims to quantify the response of a westerly-trough rainfall episode that occurred in summer 2020 to multi-scale topographic control in southwestern China,based on observations and numerical simulations.The multi-scale topography is composed of the Tibetan Plateau,Hengduan Cordillera(HC),and Sichuan Basin(SB).The westerly trough was characterized by southeastward deepening together with an in-phase propagating rainfall episode.By utilizing the results of numerical experiments,how the multi-scale topography impacted this westerly trough rainfall episode is explored.It is found that HC was the pivotal topographic factor affecting the southeastward extension of the trough and related rainfall,while SB accerelated the eastward movement of the westerly trough and changed the tilting direction of the trough line,thus further changing the location and orientation of precipitation.For extreme rainfall with intensity exceeding 10 mm h^(−1),a roughly threefold rise in the cover ratio(from 1.8% to 7.2%)and fourfold increase in the areal rainfall amount per hour occurred by removing the HC barrier,due to the strongest vorticity and long-distance transport capacity to potential vorticy mass accompanying the southeast-stretching trough.Our results quantitatively reveal a strong response of westerly trough rainfall to multi-scale topographic control in southwestern China,therefore serving as an important reference for future decision making and effective model improvement.中国西南部地形复杂,降水频发,地形对降水的影响至关重要.本文基于观测和数值模拟,定量揭示了青藏高原,横断山脉和四川盆地多尺度地形对该地区西风槽降水的影响.发现横断山脉是影响槽东南伸展,降水传播的关键地形要素,而四川盆地可加速西风槽东移,改变槽线倾斜方向,进而改变降水的位置和方向.对于极端降水事件,移除横断山脉屏障后,降水覆盖率约增加3倍(从1.8%增至7.2%),小时面雨量增强4倍.这些研究,可为地形复杂地区降水的未来预报决策和有效模式改进提供参考.

关 键 词：Heavy rainfall TROUGH TOPOGRAPHY Numerical simulation 

分 类 号：P426.6[天文地球—大气科学及气象学]