广西春夏季旱涝的等级划分及时空分布特征分析

Dryness and Wetness Grades and its Temporal and Spatial Distribution Characteristics in Spring and Summer in Guangxi

利用广西80多个站点1961～2006年的逐月降水资料，采用Z指数定义方法，对广西春夏季的旱涝进行等级划分。利用经验正交函数（EOF）分析方法对春夏季旱涝等级的时空分布进行研究，给出了四个旱涝典型场的分布特征．分析结果表明：全区性偏涝或偏旱是春夏季旱涝分布的最主要型态；春季和夏季的前4种分布形态都通过了显著性检验，两个季度的第一、第二分布形态都是全区一致型和南北反向型；春季近5年时间系数多为正值，说明近年来全区春季表现为偏旱；1990年以后，夏季第一特征向量时间系数只有3年为正值，其余均为负值，说明近16年广西夏季降水较多，以偏涝为主，年代际变化也较明显。

The dryness and wetness of spring and summer were graded according to the analysis of monthly precipitation at 80 stations from 1961 to 2006. EOF analysis shows four typical situations of the dryness and wetness distribution characteristics. The result proves： （1） In spring and summer, the whole rainfall around the province is always either greater or less than normal that is the uppermost type of the dryness and wetness situations; （3） the positive temporal coefficient of recent 5 years indicates a dryness trend in Spring; （4） All of the summer first eigenvectors are negative except 3 years that indicates a wetness trend in Summer with obvious interdecadal variations since 1990.