玉溪干旱季节分布特征及成因分析

1971～2009年玉溪市干旱发生概率最大的是冬季为85.0%,依次是春季、秋季和夏季,出现频率分别为74.4%、66.7%和33.3%。2000年以来,随着全球气候变暖,干旱发生的概率增大,特别是重旱到特旱年发生次数与20世纪相比明显增多,其中除春季变化不大外,冬、夏季分别增加了8%、6.7%,秋季增加最大为12.8%。造成玉溪干旱灾害的原因主要是冬春季受较强的偏西气流控制,夏秋季西太平洋副热带高压异常偏强、印度季风异常活跃等大气环流异常,另外自然地理复杂、生态环境遭破坏也是干旱增多的因素之一。

DISTRIBUTION AND CAUSE ANALYSIS OF DRY SEASON IN YUXI

During 1971 -2009, the most possible season which drought happens is winter. The probability is 85% the decrease order of probability of rest seasons is spring （74. 4% ）, autumn （66. 7% ） and summer （33.3%） . Since 2000, as global warming, the probability of drought has increased. Especially heavy drought and severe drought in each year have evident increase compared with the 20th century. Among all seasons, the probability increased significandy except spring, it increased by 8 % in winter, 6.7% in summer, and in autumn where increased the most, by 12. 8%. The main reason which causes drought disaster in Yuxi is atmospheric circulation anomaly, includes the control of strong air stream inclined to west in winter and spring, abnormally strong western pacific subtropical high in summer, and abnormal activity of the India monsoon. In addition, the complexity of physical geography and ecological environment destroy also caused the increase of drought.