龙卷风参数趋势性和相关性特征分析

Analysis of trend and correlation characteristics of tornado parameters

龙卷风参数的时空特性分析,对于了解龙卷风特征、致灾特性及龙卷风风灾评估等具有重要意义。本文结合Cox-Stuart和Mann-Kendall方法,对美国和中国龙卷风的年发生频次、年平均强度和年平均尺寸进行了趋势性检验。通过Pearson系数从整体上研究了不同地域龙卷风年频次的空间相关性特征,以及空间相关性与地理距离之间的关系;进一步采用Moran′s I指数度量了不同地域上龙卷风年频次的空间自相关性随时间变化的规律,分析了龙卷风发生的空间集聚性特征。结果表明:(1)美国龙卷风特征参数均表现出了逐年显著变化的趋势,中国龙卷风年频次具有减少趋势,而其他参数没有显著变化的趋势;(2)空间相关系数受到地形的影响,而不完全与空间距离成反比;(3)美国以州为单位分割下的龙卷风年频次的空间自相关关系逐年增强,龙卷风表现出逐年集聚的现象;不同空间距离下的中国龙卷风年频次的空间自相关关系逐年减弱,猜测中国龙卷风的发生在空间上越来越分散。

Analysis of the spatiotemporal characteristics of tornado parameters is of great significance for understanding the characteristics of tornadoes, the characteristics of disasters and the assessment of tornado disasters.Combined with Cox-Stuart and Mann-Kendall methods, the trends of annual frequency, average strength and annual average size of tornadoes in the United States and China are analyzed in this study.The spatial correlation characteristics of tornado annual frequency in different regions are studied based on Pearson coefficient, and the relationship between tornado frequency and geographical distance is investigated. Furthermore, Moran′s I index is used to measure the spatial auto correlation of tornadoes in different regions and also its variation with time, from which the spatial clustering characteristics of tornadoes are revealed.The results show that:(1) Characteristics parameters of tornado in United States have significant trend,the annual frequency of tornadoes in China has a decreasing trend, while other parameters have no significant trend.(2) The spatial correlation coefficient is affected by the topography, but not completely inversely proportional to the spatial distance.(3) The spatial autocorrelation of tornado frequency in the United States is increasing year by year, and the tornadoes show the phenomenon of gathering year by year. The spatial autocorrelation of the annual frequency of Chinese tornadoes at different spatial distances has been weakened year by year, and it is speculated that the occurrence of Chinese tornadoes is becoming more and more scattered in space. Correlation analysis of tornado characteristic parameters, provides the reference for understanding the temporal and spatial variation of tornadoes,and the establishment of probability model of tornado parameters.