南方冰冻雨雪灾害年的环流及气象要素异常的统计分析

利用NCEP/NCAR的2.5°×2.5°格点的逐日再分析资料,通过分析我国南方19个冰冻雨雪灾害年的36个冰冻雨雪天气个例的环流形势,总结了发生冰冻雨雪天气的4种天气类型:北脊南槽型、乌山脊型、横槽南支型和高纬低涡型,后两种天气类型持续时间长、影响范围广,极易造成南方严重的持续冰冻雨雪灾害;进一步分析南方持续冰雪天气的物理量场和要素场特征,结果表明,对流层低层850~700 hPa辐合中心较垂直上升速度中心提前1~2 d出现,预示低温雨雪增强;冻雨严重年份在700 hPa维持大于0℃的融化层,南支槽前的西南急流为雨雪天气提供了水汽和热量输送,这种配置利于冻雨天气的发展和维持。天气类型的建立及气象要素的统计有利于为南方冰雪灾害天气预测预警服务。

STATISTICS ON CIRCULATION AND METEOROLOGICAL ELEMENTS ANOMALIES DURING EXTREME FREEZING RAIN AND SNOW DISASTERS IN SOUTHERN CHINA

The circulation of 36 extreme freezing rain and heavy snow events of 19 freezing and snow disaster years in southern China was analyzed using daily NCER/NCAR 2.5°×2.5°daily reanalysis data.Four weather patterns were summarized as follow:ridge emerged in north accompany with groove in south;the Ural type;horizontal groove with southern branch type and higher latitudes vortex type.The latter two types might cause great disaster.The physical parameter fields of those processes were also analyzed.The result revealed that the convergence center at 850~700 hPa became obvious on 1~2 days advanced the vertical speed center,forebode the increase of freezing rain and snow.In the serious freezing disaster year,a warm layer(temperature>0℃) often occurred at 700 hPa,and southwest jet provided water vapor and heat for the maintenance of freezing rain.The results provide practical application to the prediction and early warning of the freezing and snow disaster in southern China.