摘要
利用第二次青藏高原科学考察及其他数据,结合5层网格嵌套、高分辨率(最高333 m)的WRF(Weather Research and Forecasting)可分辨云数值模拟,研究了局地山谷风环流在青藏高原东南林芝地区2019年9月17~18日一次地形云和降水形成过程中的作用。结果表明,此次降水过程由西风槽天气过境造成,林芝位于西风槽底部,具有弱不稳定层结,云和降水过程呈现明显的午后、傍晚和凌晨三个阶段的变化特征,并且发现局地山谷风环流在这三个阶段的变化中具有重要作用。午后阶段,由于山区强烈的太阳辐射加热,首先产生明显的上坡风和强上谷风环流,在山坡迎风坡受阻挡抬升,并激发出强的地形波,产生了强对流云和降水;傍晚阶段,由于山脉强烈的长波辐射冷却效应,产生的强下坡风在谷底辐合抬升,促进了山谷上空的弱对流、层状云发展;凌晨阶段,下坡风达到最强,产生了强下谷风环流(山风),下坡风在谷底产生强烈的抬升作用,形成深厚的层状云降水过程。
The role of local mountain-valley wind circulation in an orographic cloud and precipitation event during September 17–28,2019 in the Nyingchi region of southeastern Tibetan Plateau is investigated using the data of the Second Tibetan Plateau Scientific Expedition and numerical simulation results with the five-nested domain and high esolution(333 m)of the Weather Research and Forecasting(WRF)model,The results show that the precipitation event was caused by a passage of a westerly trough,and Nyingchi station is located at the base of the westerly trough with weak and unstable stratification.The orographic clouds and precipitation event consisted of clear three-stage variations in the afternoon,evening,and night,with the local mountain-valley wind circulation playing an important role in the variation.In the afternoon,the strong solar radiation heating first generates apparent upslope winds and produces strong upvalley winds,blocked and lifted in the windward slope,and induces strong mountain waves,as well as strong convective clouds and precipitation.In the evening,the strong longwave radiation cooling forms obvious downslope winds,causing the convergence and lifting of warmer air in the valley,thereby enhancing the formation and development of weak convection and stratiform clouds in the valley.At nighttime,the downslope winds become the strongest,the downvalley winds(mountain winds)are further enhanced,and the strong lifting generates deeper stratiform clouds.
作者
李嗣源
郭学良
唐洁
亓鹏
LI Siyuan;GUO Xueliang;TANG Jie;QI Peng(State Key Laboratory of Severe Weather,Chinese Academy of Meteorological Sciences/Key Laboratory for Cloud Physics,China Meteorological Administration,Beijing 100081;Key Laboratory for Clouds and Precipitation Physics and Severe Storms,Institute of Atmospheric Physics,Chinese Academy of Sciences,Beijing 100029)
出处
《大气科学》
CSCD
北大核心
2023年第5期1576-1592,共17页
Chinese Journal of Atmospheric Sciences
基金
第二次青藏高原综合科学考察——极端天气气候事件与灾害风险2019QZKK0104
中国气象科学研究院发展基金2020KJ016。
关键词
云和降水
山谷风环流
林芝地区
青藏高原
Clouds and precipitation
Local mountain-valley circulations
Nyingchi region
Tibetan Plateau
