2011年全球重大天气气候事件及其成因

2011年，全球气温偏高，为有观测记录以来的第十个暖年，是近60年来出现拉尼娜事件的年份中全球气温最高的一年。2011年，全球热带气旋活动较常年偏少。4月，一次拉尼娜事件结束，9月又一次拉尼娜事件生成。年初，低温、寒流席卷亚洲大部，暴风雪频繁袭击北美地区。西欧和中国东部出现严重春旱。夏季，非洲东部经历了20世纪80年代以来最严重的干旱，而东南亚、巴基斯坦和中南美洲洪涝灾害严重。全球极端偏暖事件主要出现在欧洲西部和西北部、南亚南部、东亚中西部、北美东南部等地；极端偏冷事件主要出现在东亚、澳大利亚、非洲南部和美国东北部和西部等地。而南美中东部、东南亚及中国东南部、日本、澳大利亚北部、非洲西部等地出现了极端强降水事件。研究发现，2010／2011年拉尼娜事件和台风活动是导致东南亚洪涝出现的重要原因，而巴基斯坦洪涝主要与印度洋正位相偶极型海温分布有关。

Global Significant Weather and Climate Events in 2011 and the Possible Causes

Year 2011 has been the tenth warmest year on record, and has likely been warmer than any previous La Nina years. Global tropical cyclone activity was below average in 2011. The La Nina event came to the end in April 2011, and a new event occurred in September 2011. In early 2011, extreme low temperature and cold waves blanketed most Asian and consecutive snow storms hit North America. Severe droughts occurred in West Europe and East China in spring. During summer, eastern Africa suffered the most severe drought since the 1980s, while rain storms and floods raided Southeast Asia, Pakistan and Central and South America. The central type La Nina event, together with the frequent typhoon activities, resulted in the flood in Southeast Asia. And the positive phase of the Indian Ocean Dipole (IOD) may be an important external forcing impacting the flood in Pakistan.