近几十年来冻雨时空分布特征分析

利用EC再分析资料和中国台站资料,本文分析了1978-2002年53次低温雨雪冰冻事件中的冻雨过程,确定了冻雨易发区域,并讨论了其强度变化特征.结果表明近几十年来冻雨强度呈现明显下降的趋势,且1990年是其强度变化的突变点.其次,比较了衡量冻雨强度变化的两种常用指标:冻雨发生的站次数及冻雨事件的持续时间,分析显示它们之间存在显著的相关,即两种方法衡量在冻雨强度方面是等效的.最后,通过对53次事件中的温度层结及环流形势进行合成分析和经验正交分解(EOF),揭示了逆温层不但是冻雨发生的必要条件,而且也是冻雨强度发展的调节器.

Analysis on the Spatial Temporal Characteristics of Freezing Rain in Recent Decades

Using EC reanalysis data and the data from observation stations in China, this study analyzes the 53 freezing rain processes which occurred during the period 1978-2002, defines the incidental region and discusses the variability of their spatial temporal features in recent decades. The result shows that the intensity of the freezing rain events these years has a significant decreasing trend, whose break point happened in 1990. Then, two kinds of norms that measure the intensity of freezing rain: the number of stations that experienced the freezing rains and the durations are compared, finding close connections in them. The effects of the two methods used for describing the variability of freezing rain are similar. In addition, through the methods of composite analysis and empirical orthogonal function (EOF), it is revealed that the reverse layer is not only the essential requirement for producing freezing rains, but also acts as an intensity adjustor of the change of freezing rain intensity.