东北地区暴雪天气的统计学划分方法及其时空分布特征

应用近49 a东北地区200个气象站冬半年降水资料和相对应的NCEP/NCAR 2.5o×2.5o温度场再分析资料,提出了基于降水相态变化特征的东北地区暴雪天气划分的统计学方法,将东北地区暴雪分为纯雪型暴雪(Ⅰ型暴雪)和雨雪混合型暴雪(Ⅱ型暴雪)两大类,并根据影响范围将其划分为大范围暴雪、区域暴雪和局地暴雪3类。在此基础上分析了不同类型东北区暴雪的时空分布特征。结果发现:两型暴雪出现频次基本相当,Ⅱ型大范围暴雪明显多于Ⅰ型,局地暴雪则相反;东北地区暴雪的年际变化较大且具有明显的年代际特征,20世纪70年代后期至80年代中期Ⅰ型暴雪明显多于Ⅱ型,21世纪初期Ⅱ型暴雪多于Ⅰ型,表明全球变暖在中国东北的区域响应显著;东北区暴雪主要集中在秋末和初春两季,但两型暴雪起止时间和峰值都不相同;两型暴雪出现频次都呈东多西少的分布,其中Ⅱ型暴雪频次自东南向西向北减小的梯度更大。从结果来看所提出的划分办法很好的反映了不同降水相态的东北地区暴雪的发生和变化规律具有很大差别,这种差异与以往东北地区暴雪个例的分析工作中反映的情况是一致的;证明了本划分方法是合理的,具有实际工作意义。

Classification and Features of Spatio-temporal Variation of Snowstorms in Northeast China

By using precipitation data of 200 stations in the winter half Year(from October to next May) in Northeast China and NCEP / NCAR temperature reanalysis data with a horizontal resolution of 2.5o× 2.5o,a classification of snowstorm events in Northeast China is proposed based on phase features of water content in the precipitation.The snowstorm events can be grouped into two categories: one with only pure snowfall(Type I) and the other with snow and rain mix(Type II).And each type can be further classified into three groups,namely,extensive,regional and local range according to the area affected.On this base,the spatial and temporal characteristics of different types of snowstorms in Northeast China are studied.It is showed that the two types bear basiclly the samef requency of occurrence,however,with respect to extensive-range events,the type II is much more frequent than the typeⅠ,while for local snowstorms the situation is reversed.There are substantial interannual variations of the snowstorm events in Northeast China,and the interdecadal characteristics are also obvious.The frequency of type Ⅰwas significantly higher than type Ⅱ during the late 1970’s to the mid 1980’s,and the reverse appeared in the beginning of 2000’s,which might imply the response of climate in Northeast China to the global warming.Snowstorms in Northeast China mainly occur in late autumn and early spring,but the timing of their beginning,ending and peak of activity are different for the two types.The frequency of snowstorm decreases from the west to the east for both types,but the decrease is even sharper from the northwest to southeast for the type II events.The results suggest the classification approach proposed well reflects the difference of two types of snowstorm process in Northest China in terms of their spatio-temporal variations.The results are also in agreement with previous case studies,which may justify,to some extent,the rationality of the method proposed,and its usefulness for the coming practical works.