贵州冬季冻雨研究综述

A Review of of Freezing Rain in Guizhou

贵州是我国冬季出现冻雨灾害最多的省份,冻雨气象灾害对交通运输、能源电力、农林业和居民生活等方面带来了严重影响。该文阐述了贵州冻雨的气候特征,分别从气候背景、天气形势、温湿度垂直结构特征等方面探讨了冻雨天气过程发生、发展、维持和消亡的物理成因和机理,并对贵州冻雨的预报预测方法作了概述。结果表明,海温异常通过海气相互作用对大气环流造成影响,尤其在赤道中东太平洋海温负异常(La Nina事件)的气候背景下,利于中高纬地区欧亚阻塞环流形势的形成,中高纬地区呈"北高南低",中亚、西亚低槽(涡)稳定且活跃,东亚冬季风加强,中纬度大气环流的经向度加强,强冷空气频繁南侵,造成我国南方大部地区气温偏低,长江以南地区降水偏多,促使贵州地区低温雨雪冰冻天气的形成;利于副热带地区西太平洋副高强盛,偏西、偏北,副热带锋区强盛,中低纬地区呈"西高东低",南支低槽系统活跃加深,西南低空急流强盛,使南海及孟加拉湾持续不断地向贵州地区输送西南暖湿气流,有利于中层的增温增湿,为该地区冻雨发生提供了充沛的水汽条件以及热量和动量。由于贵州特殊的地形地貌和气候特征,冬季北上的暖湿气流和南下的冷气团易受地形阻挡形成滇黔准静止锋,在垂直方向上呈"干冷—暖湿—干冷"的结构特征,锋面逆温的长时间维持是贵州冻雨持续发生的必要条件。

Guizhou is a province with frequent freezing rain disaster in winter in China.Freezing rain disaster has affected transportation,energy and power,agroforestry,and residents’life,etc.This paper expounded the climatic characteristics of freezing rain in Guizhou Province,and discussed the physical causes and mechanisms of its occurrence,development,maintenance and extinction from the aspects of climatic background,weather situation and vertical structure of temperature and humidity.The results show that the SST(sea surface temperature)anomaly influences the general circulation through the interaction of air and sea,especially under the climate background of the negative SST anomaly in the equatorial Middle East Pacific(La Nina event).When a Eurasian blocking circulation is formed in the middle and high latitudes,it strengthens the East Asian Winter Monsoon and the meridional degree of the mid latitude atmospheric circulation,stabilizing and activating the low troughs(vortices)in Central and Western Asia,where the middle and high latitudes are high in the north and low in the south.The frequent cold air activities are conductive to the southward invasion,causing low temperature in most areas of South China and excessive precipitation in the south of the Yangtze River which promotes the formation of cold rain,snow and freezing weather in Guizhou Province.The negative SST anomaly in the equatorial Middle East Pacific is conducive to strengthening subtropical high in the Western Pacific and moving to the west and north,activating and deepening the South Branch low trough system,and brings about the low-level southwest jet powerful and prosperous,with the middle and low latitudes“high in the West and low in the East”.It makes the South China Sea and Bay of Bengal continuously transport southwest warm and humid air to Guizhou province,which is beneficial to the temperature and humidity increase in the middle layer,and provides abundant water vapor conditions,heat and momentum for the occurrence of freezing rain in this area.Due to the special topography and climate feature,the warm and humid air flow from the north and the cold air mass from the south are easily blocked by the terrain to form the quasi static front of Yunnan and Guizhou,which is characterized by a“dry cold-warm wet-dry cold”structure in the vertical direction.The long-term maintenance of frontal inversion is the necessary condition for the continuous occurrence of freezing rain in Guizhou province.