云南寒潮的气候特征及其不同路径的大气环流差异

Analysis of climatic characteristics of cold waves and atmospheric circulations along different routes in Yunnan

利用云南省125个气象站1981—2021年逐日平均气温和最低气温的资料,分析了云南省寒潮天气的气候变化特征及大气环流特征.结果表明:①1981—2021年云南寒潮频次总体呈减少趋势,12月至次年1月为寒潮多发期,云南寒潮类型以低温寒潮为主;②当极涡偏强、贝加尔湖阻塞高压偏强、东亚大槽和南支槽偏强、西太平洋副热带高压偏弱偏南及东亚地面冷高压偏强时,云南寒潮频次偏多;③造成云南寒潮的3条路径中,东北路径和偏东路径占比达到90%以上.西北路径寒潮发生最少,通常伴随着大幅的最低气温下降,常造成云南重霜冻天气,大部分的西北路径寒潮发生在东部路径寒潮的中后期;④云南西北路径寒潮相较东部路径寒潮地面冷高压位置偏西偏强,南支槽偏东,高空冷平流偏强,低纬度西风带风速偏弱,青藏高原东南侧下沉气流偏强.

The climatic change characteristics of cold waves and atmospheric circulations in Yunnan are analyzed,based on the daily mean temperatures and minimum temperatures of 125 meteorological observation stations in Yunnan Province from 1981 to 2021.The results indicate that:①The cold wave frequencies in Yunnan show a decreasing trend from 1981 to 2021.In the province,cold waves happen most frequently in December and the following January;and most of the cold waves are a minimum temperature type.②More frequently the cold waves will happen in Yunnan,when the polar vortex is stronger than normal,the Baikal blocking high is stronger than normal,the deep East-Asian trough and the Southern Branch trough are stronger than normal,the West Pacific subtropical high is weaker than normal and the East-Asian surface cold high is stronger than normal.③The cold waves along the Northeastern route and those along the Eastern route account for more than 90%of all the three routes of cold waves in Yunnan.The frequency of cold waves along the Northwestern route is the lowest,usually accompanied by a sharp drop to the lowest temperature,which often leads to severe frost weather in Yunnan.Most of the cold waves along the Northwestern route occur in the middle and late stages of the Eastern route cold waves.④Compared with the cold waves along the Eastern route,the surface cold high of cold waves along the Northwestern route in Yunnan extends westward and is stronger,the Southern Branch trough extends eastward,the upper cold advection is stronger,the wind speed in the low latitude westerlies is slower,and the downdraft in the Southeast of the Tibetan Plateau is stronger.