1960—2009年中国夏季极端降水事件与气温的变化及其环流特征

Change Properties of Summer Extreme Precipitation Events and Temperature and Associated Large-Scale Circulation in China during 1960—2009

使用1960—2009年中国610个气象站逐日降水和气温资料及NCEP再分析资料,采用奇异值分解方法研究了近50年中国夏季平均气温与极端降水事件频数的关系,并对比分析了两者变化相应的大气环流差异。结果表明,我国的西北和长江以南地区极端降水事件频数与气温呈正相关关系,而东北—西南走向一带为负相关关系。夏季气温和极端降水事件均在1992年左右发生突变。突变前850hPa风场存在一个中心位于内蒙古的异常大陆气旋环流,而突变后变为异常大陆反气旋环流,这个异常气旋(反气旋)会增强(削弱)冷空气南侵入我国,从而导致我国气温突变后高于突变前。突变前,西部和长江以南地区分别为异常西风水汽输送和异常西南水汽输送,水汽均为异常辐散,极端降水事件偏少;东北—西南一带为异常西南水汽输送,水汽异常辐合,极端降水事件偏多;突变后,反之。

Climate simulations have suggested that a greenhouse-gas induced global warming would also lead to a moistening of the atmosphere and an intensification of the mean hydrological cycle.Such a change can contribute directly to changes in regional precipitation climate,so there is an ongoing interest in the possible relationship between temperature and extreme precipitation events（EPE）.The relationship between summer temperature and extreme precipitation events was studied using Singular Value of Decomposition（SVD） method based on the daily precipitation and temperature data of the 610 meteorological stations in China and NCEP/NCAR reanalysis data from 1960 to 2009,the difference of their corresponding change in atmospheric circulation was also analyzed.Results show that there exists a significant correlation between EPE and temperature in China that a positive correlation in northwest and southern areas but a negative correlation in the northeast to southwestern areas.Abrupt summer temperature and EPE change both emerged around 1992,an abnormal continental cyclonic circulation whose center in Mongolia existed in 850 hPa wind fields during pre-mutation（1960 — 1992）,however,abnormal continental cyclonic circulation translated to anticyclonic circulation during later mutation（1993-2009）.This abnormal cyclonic（anticyclonic） would strengthen（weaken） the cold air invasion southward,resulting in higher temperature of the later mutation.During pre-mutation,western and southern China were respectively influenced by abnormal western and southwestern water vapor transportation,water vapor was abnormal divergence and resulted in less EPE.However,northeast to southwest areas were affected by abnormal southwestern water vapor transportation,water vapor was abnormal convergence and leaded to more EPE.The situation was just opposite after mutation.