内蒙古东部牧区极端降雪变化特征及其成因

Characteristics and Mechanism Analysis of Extreme Snow Change in Eastern Inner Mongolia Pasturing Area

利用内蒙古牧区34个地面气象站1961~2010年冬季降雪资料和NCEP再分析资料,采用趋势分析、合成分析等方法探讨内蒙古牧区极端降雪时空变化特征和形成机制,得出如下结论：内蒙古牧区极端降雪量呈自西向东逐渐增多趋势,近20 a变化表明内蒙古东部牧区极端降雪量呈显著增加趋势。500 hPa高度场上呈＂（乌拉尔山高压）＋（贝加尔湖低槽）-（白令海阻高）＋＂分布型时,冷空气易传输并堆积至内蒙古东北部牧区,有利于极端降雪发生。内蒙古东部牧区极端降雪发生时的主要水汽来源于北冰洋地区。Rossby波动持续东传有利于乌拉尔山高压、贝加尔湖低压和白令海高压的形成和维持。

Spatial-temporal characteristics and the formation mechanisms of extreme heavy snow over Inner Mongolia parish were analyzed using techniques of trend analysis and composite analysis,as well as data including NCEP reanalysis data and station snow data in winter over the parish.It was indicated that snowfall over the Inner Mongolia parish appeared to get increased from the west to the east during the past 20 years,with the big value area of snowfall in the mid-east area of Inner Mongolia.During the years of extreme heavy snow in the east parish,there was negative anomaly center in 500hPa height field near Baikal Lake.Code air can be transported to the northeast parish of Inner Mongolia and accumulated when there is a＂Ural High（＋）-Baikal Trough（-）-Bering Sea Blocking（＋）＂pattern in 500 hPa height field,which favors the extreme heavy snow.The Arctic areas turned out to be the major moisture sources of heavy snow over east parish of Inner Mongolia.Land-sea thermal difference resulting from Positive SST anomaly of the North Atlantic Ocean becomes Wave-Activity Flux and moves eastward,forming convergence of Wave-Activity Flux and thus leading to the persistence of high press range.Also,the persistence of eastward transmission of Rossby waves was conducive for the formation and persistence of the Ural High,Baikal Trough and Bering Sea Blocking,and the favorable distribution of extreme heavy snow over Euro-Asian Continent.