2008年初广西异常低温雨雪冰冻天气影响因子分析

Analysis on Influence Factors of the Abnormal Low Temperature,Sleet and Frost Weather in Guangxi at the Beginning of 2008

2008年1月12日至2月20日,广西出现了1951年以来持续时间最长,平均气温最低的低温雨雪冰冻灾害天气过程,过程气温偏低程度达到了异常偏低的标准。利用数理统计、对比分析方法对广西历史上同期6次严重低温过程与2008年低温雨雪过程环流形势和主要影响因子进行了分析,并对相关性显著的4种环流指数进行了经验模态分析。结果表明:北半球500 hPa环流为偶极型,欧亚大陆中高纬度和北太平洋地区为持续稳定的高压脊,同时巴尔喀什湖以南的青藏高原地区及孟加拉湾地区为持续稳定的低压槽,这种"北脊南槽"分布形势是造成广西异常低温过程的主要环流背景;蒙古低槽、孟加拉湾低槽、东北太平洋阻高持续偏强,及副高西伸脊点位于南海至菲律宾一带海面的日数偏多是2008年初广西异常低温雨雪天气过程的主要影响因子,它们组合异常,导致了广西异常低温雨雪天气的发生。

During January 12 to February 20 of 2008,the low temperature,sleet and frost weather process occurred in Guangxi,whose duration has been the longest and the average temperature has been the lowest since 1951,and the accumulative temperature of the process reached the standard level of abnormal low. Circulation features and indices of six remarkable low temperature and sleet processes at the corresponding period in Guangxi were analyzed,then EMD（empirical mode decomposition）research was carried out for four kinds of circulation indices which are obviously correlated,results showed that major circulation characteristics of abnormal low temperature of Guangxi are of dipole type at 500 hPa circulation in the Northern Hemisphere,therefore,there are stable high ridges over high and mid-latitudes of Asia and North Pacific, and it also has the stable trough over the Qinghai-Tibetan Plateau and the Bay of Bengal at the same time. These are the major circulations for abnormal low temperature weather in Guangxi.The stronger trough over Mongolia and the Bay of Bengal,the stronger blocking-high,and more days for the westward extension of the subtropical-high ridge from the South China Sea to Philippines,all these are the main influence factors for the low temperature,sleet and frost weather process,so that the low temperature,sleet and frost synoptic process happened in Guangxi at the beginning of 2008 when these conditions are satisfied.