中文摘要：

2005年春季云南出现了自1979年以来大范围持续性的干旱天气,给工农业生产和人民生活造成了巨大损失。首先对这次持续性异常干旱的成因进行诊断分析,然后通过相关分析和合成分析方法进一步探讨了云南春旱发生的前期信号特征。结果表明：（1）这次云南春旱发生时大气异常状态特征主要表现为干燥的对流层大气和强烈的下沉运动。（2）850hPa北印度洋地区持续的东风异常和持续偏强偏西的西太平洋副热带高压是导致这次云南重大春旱发生的重要原因。（3）前期冬季1～2月东亚中纬度地区对流层低层或中高层较强冷空气的向南输送,以及1～3月赤道附近弱对流活动有利于云南春季降水偏少,对后期云南春旱的发生有重要的指示意义。

英文摘要：

A widespread drought occurred over Yunnan during the spring of 2005, the most serious since 1979. This drought weather caused heavy losses to the industrial and agricultural production as well as people＇s life and property in the province. A preliminary diagnostic study is firstly made here to probe into the forming causes of the drought. The results show that the drought weather is associated with persistent anomalous westly wind at 850 hPa over the basin of northern India Ocean and a subtropical high that is stronger and more westward located. Then, early signal characteristics of the drought climate are further investigated by using the methods of correlation and composite analyses. The results show that the southward flow of stronger cold air at lower or mid-higher troposphere and weaker convection near the equator region during early winter are favorable for droughts to appear and can be considered as important early signal characteristics of precipitation anomaly in subsequent Yunnan springs.