湖南汛期降水分区和变化规律的探讨

REGIONAL ASSIGNMENT OF PRECIPITATION DURING THE FLOOD SEASON IN HUNAN AND REGULARITIES IN THE DYNAMICS OF THE RAINFALL

利用湖南５２ 站汛期（４ ～９ 月） 降水资料，根据聚类分析方法，进行降水分区，结果共分为Ⅰ区（ 湘西） 、Ⅱ区（ 湘北） 、Ⅲ区（ 湘东） 、Ⅳ区（ 湘中） 和Ⅴ区（ 湘南） 等５ 个区域，能反映地理位置和地形对降水的影响。然后，通过统计分析，讨论了各区域汛期降水的年际变化趋势，结果表明，Ⅱ区（ 湘北） 汛期降水的年际变化最大；同时，根据各区域汛期降水的距平资料，探讨了它们的变化规律，结果显示，基本上都呈现出上升—下降—上升的特征，只有Ⅴ区（ 湘南） 稍有差异。文中利用最大熵谱分析方法，揭示了各区域降水的主要周期，并探讨了各区降水与厄尔尼诺的关系，分析了Ⅱ区（ 湘北）

Method of cluster analysis was used in this paper for assigning various regions in terms of precipitation during the flood season of Hunan on the basis of the rainfall data from 52 meteorological stations (from April to September) in Hunan.Results show that 5 regions are recognizable:Ⅰ West Hunan,Ⅱ North Hunan,Ⅲ East Hunan,Ⅳ Middle part of Hunan,Ⅴ South Hunan.The influences of geographical location and topography are reflected.The trends of interannual change of the rainfall in each region are discussed.The change in the amount of orecipitation is the greatest in North Hunan.Then the regularities governing the change studied.Results show that features of rise drop rise in the rainfall are evident,only Ⅴ South Hunan was trifle different.Its main periods are revealed with maximum entropy spectrum analysis.The relationship between the precipitation of each region and EI Nino is studied Analysis reveals that it is apt to have flood occured in the subsequent year following EI Nino in the area of Dongting Lake.