基于GIS的贵州省冰雹分布与地形因子关系分析

Hail Distribution and Topographical Factors in Guizhou Province Based on GIS Technique

使用贵州省1961—2004年84个气象台站44年历史冰雹记录及1:1000000全国数字高程模型(DEM)资料,采用基于GIS的数字地形分析、分区统计和图像分类方法,研究了冰雹分布与地形高程、坡向、坡度及地形切割深度的关系。研究表明:地形高程是影响贵州省降雹分布的最主要地形影响因子;微观地形因子如坡向和坡度对降雹日数的变异并没有显著性影响,但大范围的地势抬升及暖湿空气的迎风坡有利于降雹;地形切割深度并不是年平均降雹日数差异的显著影响因子;纬度位置的不同,使其受暖湿空气影响程度不同,热力条件也存在差异,也是影响平均降雹日数差异的因子之一;根据3个影响因子建模获得的方程及贵州省冰雹风险分区图,经统计检验和与历史乡镇降雹资料比较,具有较好的一致性。

Research on the relationship of topographical factors to distribution of hail, and getting an image of subdivisions for hail hazard which quantificationally concerns the difference of topographical factors are important to hail weather forecasting. Also, best services for decision-making to disaster prevention and reduction is provided. The relationship between distribution of hail and some topographical factors, such as elevation, slope grade, slope aspect and terrain incision depth, are studied by using GIS techniques, such as digital terrain analysis, zon- al statistics and image classification with historical hail records of 84 meteorological stations over 44 years in Guizhou Province and the 1：1000000 resolution DEM data of China. It shows that natural logarithm of mean annual hail days conforms to normal distribution . The elevation is the major topographical factor which primarily influence the distribution of hail, the annual mean hail days increase with the increase of elevation and it increases remarkably as the elevation increases to about 1000-1500 meters. Micro topographical factors, such as slope grade and slope aspect, are not remarkable factors to the variance of annual mean hail days, but topography rising over large area and windward slope of warm moist air are favorable to hail. Terrain incision depth is not remarkable factor to the difference of annual mean hail days either. Different latitude is also one of the factors which influence the difference of annual mean hail days. The model for annual mean hail days derived from the three remarkable factors and the map of hail hazard evaluation are reliable via statistical test and comparison to historical hail reports over countryside spots. The analysis is influenced due to the lack of hail reports in inner mountainous area in Guizhou and the incomplete collection of hail reports data. The relationship between different topographical factors should be further studied.