2011年海洋和大气环流异常及对中国气候的影响

Anomalies of Ocean and Atmospheric Circulation in 2011 and Their Impacts on Climate in China

本文基于实时和历史观测资料,利用气候统计和气候机理诊断方法,对2011年气候异常及成因进行总结分析。结果表明,全球海洋外源强迫和大气内部动力过程共同作用下的大气环流系统组合异常,是造成2011年中国大部地区降水异常偏少,温度明显偏高,呈现暖干型气候特征的主要原因。具体表现为,拉尼娜事件在2011年夏季短暂中断后,9月再次进入拉尼娜状态;西太平洋副热带高压在5月之前异常偏弱、偏东,致使长江中下游出现严重春旱,之后副热带高压有所加强,尤其在6月异常偏强,使长江中下游地区梅雨量偏多、旱涝急转;秋季副热带高压脊线偏北、中高纬度冷空气活动阶段性活跃,致使华西、黄淮地区秋雨异常偏多;热带印度洋海温演变经历负偶极型海温模态后,夏季转为全区一致型暖海温;2010/2011年东亚冬季风偏强,2011年南海夏季风爆发偏早、结束偏晚,东亚夏季风正常偏弱;西北太平洋和南海热带气旋生成数量处于偏少的年代际时段,2011年热带气旋生成数量偏少。

Based on the real-time and historical observation data, the climatic anomaly of 2011 in China and its causes were analyzed by climate statistics and climate diagnostic methods. The result showed that glob- al ocean sea surface temperature forcing and the atmospheric circulation abnormality features attributed tothe internal atmospheric dynamic processes, may lead to the climatic anomalies and major climate events in China, with such significant anomalies of climatic features as less precipitation, higher air temperature and warm-dry type in 2011. Results manifested that the eastern and central equatorial Pacific entered the LaNina conditions again in September 2011, with the La Nina event of 2010/2011 starting at July 2010 and ending in April 2011; The subtropical high over the West Pacific （SHWP） was abnormally weaker than normal and further east to its normal position before May 2011, which resulted in severe meteorologicaldrought in the Middle and Lower Reaches of the Yangtze River during spring, while SHWP stronger than normal from then on, especially abnormally stronger in June, which led to more Meiyu precipitation amounts and rapid transition between drought and flood in the Middle and Lower Reaches of the YangtzeRiver; The SHWP was further north to its normal position in autumn, together with the phased cold air activities, those resulted in more precipitation during the season in the area of Huaxi and Huanghuai. Thetropical Indian Ocean SSTA firstly experienced negative Indian Ocean Dipole （IOD） mode in 2011, then turned into the basin-wide warming mode in summer. The East Asian winter monsoon （EAWM） intensity was stronger than normal in 2010/2011 winter, while intensity of the East Asian subtropical summer mon-soon （June--August） was near normal. The intensity of the South China Sea （SCS） summer monsoon was weaker than normal on the whole, with the earlier onset and later ending. In accord with the decadal back- ground, tropical cyclone generated number was less than the normal in the SCS and West Pacific in 2011.