中文摘要：

针对目前各种干旱指数对干旱事件整体识别能力的局限性，采用一种新的客观识别方法“区域性极端事件客观识别方法（ OITREE）”对2009~2010年中国西南地区的秋冬春连旱进行了特征识别。结果表明：（1）此次干旱事件的发生时段为2009年8月25日至2010年4月18日，历时237 d，为近50 a（1961~2010年）综合强度排名第五位的干旱事件，是一次极端干旱事件；（2）此次极端干旱过程最大影响面积为576.82万km2，影响范围涉及到云南全省、四川南部、贵州大部（主要是西部）以及重庆、广西西部，其中，云南、贵州和广西3省交界区干旱最严重，其次为云南的中部和中西部，且云南省不论受旱面积还是受旱强度都是最大的；（3）此次干旱过程有4个明显变化阶段：干旱增强、减弱、再增强、最后解除。第一阶段为2009年8月25日至10月下旬，干旱开始发展并持续增强，影响范围最大可达约370万km2，包括西南、华南、华东、华北及东北南部的小部分地区，持续达2个月，受影响的核心区域除了西南地区以外，还有华北和华南的部分区域；第二阶段为2009年11月初至12月中旬，干旱强度急剧下降，影响范围最小只有约50万km2，主要在西南地区，持续时间只有1个月；第三阶段，2009年12月中旬至2010年3月下旬，旱情再一次增强，干旱面积再次扩大，影响范围最大可达约200万km2，包括西南及西北地区东部，持续时间为3个月，是4个阶段中发展时间最长的，主要受影响的核心区域为西南地区；第四阶段，2010年3月下旬至4月中旬，干旱逐渐缓解，直到过程结束，旱情解除。OITREE方法能从不同层次和方面完整地描述干旱事件的时空变化特点，其判别结果与实际情况基本一致，是一种有效监测干旱的新方法。

英文摘要：

Based on the daily CI drought index from 723 observation stations in China,the characteristics of a severe drought event which occurred in southwestern China from autumn of 2009 to spring of 2010 were analyzed by using the Objective Identification Tech-nique For Regional Extreme Events（ OITREE ）. The results are as follows：（ 1 ）According to all the drought events identified by OITREE over the past 50 years,this event was the fifth serious one,that means it was a severe drought event. The drought occurred during August 25th 2009 to April 18th 2010,which went through 237 days. Besides,the drought covered the maximum region of 5 768 200 km2 and the geometric center was located in 33. 72°N,108. 9°E.（2）The impact area of the regional drought event mainly includ-ed Yunnan,southern Sichuan,western Guizhou,Chongqing and western Guangxi,specially,drought intensity was most serious in the border of Yunnan,Guizhou and Guangxi,secondly in the middle and western Yunnan. Above all,the drought in Yunnan was most se-rious.（3）There were four obvious phases in this event. The first phase was from August 25th,2009 to later October 2009,drought began to develop and strengthen continuously,and sustained for two months. The daily impact area and accumulated intensity increased and reached the maximum level among the whole event,and the core regions affected by the drought was located not only in the south-western China but also in the north and south part of China. The second one was from early November 2009 to middle December 2009, drought condition receded while daily impact area shrunk. Drought intensity strengthened again from middle December 2009 to later March 2010,it was notable that the extreme impacted area and accumulated intensity was less than that of the first phase,but the dura-tion was longer. The core region of drought was in southwestern China. Ultimately,the drought condition weakened gradually and then went to the end. Additionally,the spatial distributions of stations,extreme intensity and accum