中国南方2008年1月罕见低温雨雪冰冻灾害发生的原因及其与气候变暖的关系

Causes of the unprecedented freezing disaster in January 2008 and its possible association with the global warming.

2008年1月中国南方发生的低温、雨雪、冰冻灾害不是一个局地或地区性现象,它是同期发生的亚洲大范围冰雪灾害链中的一环,在影响范围和灾害程度上是最严重的一环。它有3个主要特征:(1)降雪、冻雨和降雨3种天气并存,冻雨是导致南方致灾的主要原因;(2)低温、雨雪、冻雨天气强度大,根据中国国家气候中心和南方各省气象部门的统计及分析,有8项气象要素打破同期中国历史记录;(3)低温、雨雪、冰冻天气持续时间长,破历史记录。这次低温、雨雪冰冻灾害形成的原因不是单一的,是多种因素在同一时段,同一地区相互配合和迭加的结果,其中La Nina事件是灾害发生的气候背景,它为雨雪冰冻天气提供了冷空气侵袭中国南方的前提条件;欧亚大气环流异常持续性是造成冷空气不断侵袭中国南方的直接原因;孟加拉湾和南海地区暖湿气流的北上是大范围冻雨和降雪形成并持续在中国南方的必要条件。

The unprecedented disaster of low temperature, persistent rain, snow and ice storms, causing widespread freezing in the Yangtze River basin and South China in January 2008 is not a local or regional event, but a part of the chain events of large-scale low temperature and snow storms in the same period in Asia. Its severity and impacts were most significant in South China. The event was characterized by three major features： （1） snowfall, freezing rain and rainfall, the three forms of precipitation coexisted with freezing rain being the dominant factor responsible for this disaster; （2） low temperature, rain and snow, and freezing rain exhibited extremely great intensity, with record-breaking measurements logged down for 8 meteorological elements based on the statistics made by China National Climate Center and the provincial meteorological services in the Yangtze River basin and South China; （3） the dis- astrous weathers persisted for an exceptionally long time period, unrecorded before in the observation history of China. There is no single cause for this event. It may be resulted from multiple factors that superimpose on and interweave with one an- other at the right time and place. Among them, the La Nina situation is a climate background that provided conducive conditions for the invasion of cold air into South China; the persistent anomaly of the atmospheric circulation in Eurasia is the direct cause for 4 rounds of cold air invasion into South China ; and the northward transport of warm and moist airflows from the Bay of Bengal and the South China Sea finally warranted the formation of the freezing rain and snow storms and their prolonged dominance in the southern part of China. A preliminary discussion of a possible association of this disastrous event with the global warming is presented. This event may be viewed as a short-term, regional perturbation to the global warming trend. There is not any possibility for this event to divert the long-term trend and the global pattern of the global warming.