云南省干旱时空演变规律及季节连旱的概率特征分析

Spatio-temporal Analysis of Droughts and the Characteristic of Continuous Seasonal Droughts Probability in Yunnan Province

选取云南省29个气象站点1960—2010年的降水数据,计算每个站点季尺度和年尺度的标准化降水指数(SPI),分析了云南省干旱的时空演变规律.在此基础上,利用广义极值分布(GEV)拟合季节SPI序列分布,通过离差平方和最小准则(OSL)法选择Frank Copula拟合各季节SPI二维联合概率分布,研究云南地区季节连续干旱及连续特旱事件的概率特征.研究结果表明,云南省在过去51年呈不显著变旱的趋势,其中,夏、秋和冬季发生干旱的频率均呈增加趋势,而春季发生干旱的频率呈减少趋势;春夏、夏秋和冬春连续干旱与连续特旱发生频率呈北多南少的规律,高频率地区主要集中在云南省西北、东北及中部,而秋冬连续干旱与连续特旱高频率地区则主要集中在云南省西南部.

Daily precipitation of 29 meteorological stations from 1960 to 2010 in Yunnan Province of China was collected to calculate the standardized precipitation index （SPI）at annual and seasonal time scale. The spatial-temporal variation of drouglat and extreme dtrought was analyzed based on the SPL The series of seasonal SPI were fit by the generalized extreme value distribution（GEV）. Frank Copula which was chosen by the method of the deviation square and minimum criterion（OSL） was used to fit the joint distribution of the series of seasonal SP! and calculate the probability of continuous seasonal droughts. Results showed that, over the past 51 years, the frequency continuous drought had showed an insignificant increasing trend in Yunnan Province. The of drought increased in summer, autumn and winter while it decreased in spring. The drought and continuous extreme drought were more likely to occur in northern part than in southern part of Yunnan during spring-summer, summer-autumn and winter-spring. High frequency of continuous drought and continuous extreme drought had been detected in the northwest, northeast and the middle of Yunnan during spring-summer, summer-autumn and winter-spring and in the southwest of Yunnan during autumn-winter.