凝冻灾害特征及其天气成因分析

Characteristics of the freezing disaster and its weather causes

利用2008年1月10日至2月2日南方特大雨雪冰冻灾害期间主要受灾地区气象观测数据,对灾害期间各地出现的天气现象及其致灾机理差异进行了分析比较,并以贵州为代表对凝冻灾害特征及其天气成因进行了分析总结,主要得到以下结论:(1)2008年初南方受灾地区西段即贵州全省、湖南西部以及云南东北部、广西北部主要是由于冻雨、湿雪造成的凝冻灾害,东段的江西、安徽、浙江等长江中下游地区主要是以雪灾为代表的冰冻灾害,而整个南方受灾地区低温雨雪混合冻结的情况比较普遍;(2)凝冻灾害的特征是在物体表面形成覆冰层,其形成过程中一般有液态水向固态冰的转化;(3)凝冻灾害具有多种覆冰致灾机制,包括雨凇、雾凇、湿雪以及雨雾或雨雪混合冻结,其危害性比一般的冰冻灾害更为严重;(4)凝冻天气现象包括冻雨、冻毛雨、雨夹雪、过冷雾、湿雪等,持续的凝冻天气过程往往出现多种凝冻天气现象的交替,造成雨凇、雾凇、雨雾混合凇及雨雪混合冻结等多种类型的覆冰,从而导致严重的凝冻灾害。这也是2008年初贵州成为全国受灾最重地区的原因。

Using ground meteorological stations observation data from January 10 to February 2 of 2008,the weather phenomena appeared at different areas and their disaster-causing mechanisms in the beginning of 2008 in southern China were analyzed and compared.Characteristics of the freezing disaster and its weather cause were analyzed and summarized with Guizhou as the representative area.The main results are as follows:(1)The cause of freezing disaster at the west part of the stricken areas is dominated by the freezing rain and mixed freezing of rain and snow,whereas at the east part of the stricken areas the havoc is mainly caused by the snowstorm.(2)The freezing disaster is characterized by the form of ice layer covering surface of ground objects,and there must be phase-change from liquid water to solid ice during its establishment.(3)There are variety of icing mechanisms of freezing disaster,including glaze,rime,rain-fog or rain-snow mixed freezing,that is rather more harmful compared to general frozen disaster.(4)Freezing weather is the cause of freezing disaster,which behaves in varied forms of weather appearances,including freezing rain,freezing drizzle,sleet,freezing fog,wet snow and their mixed freezing.Generally,a variety of freezing phenomena arise alternatively in a durative freezing weather process,giving rise to varied types of icing and leading to serious freezing disaster.That is also the reason why the disaster hardest-hit area was Guizhou province in the beginning of 2008.