利用1901—2010年GPCC逐月降水、HadISST月平均海表温度、NOAA 20世纪再分析等资料,采用最大协方差分析(Maximum Covariance Analysis, MCA)、相关、回归等方法研究了东亚地区夏季降水与全球海表温度异常之间的年代际时空变化关系。MCA分析结果表明,东亚地区夏季降水与全球海温异常耦合关系在年代际尺度上主要表现为4个模态,分别受全球变暖、太平洋年代际涛动PDO、大西洋多年代际涛动AMO和北太平洋涡旋振荡NPGO影响,各自解释了27.7%,12.5%,8.9%和7.3%的方差。第一模态由于受全球变暖影响,东亚大部分地区水汽充足,因此东亚大部分地区降水均偏多。第二模态的降水异常表现为东亚中部地区降水偏多而南部和北部偏少的“南北旱中间涝”的三极型分布,其可能原因是太平洋年代际涛动使得东亚夏季风减弱,不利于水汽往北输送,引起水汽在东亚中部聚集,导致该地区降水偏多;同时西风带往南偏移,使得东亚中部地区对流增强,也引起该地区降水偏多。第三模态的降水异常则主要为“南涝北旱”的偶极分布型,可能原因是东亚大槽向东南方向偏移,东亚北部西风带减弱,使得东亚北部对流减弱、降水偏少,而东亚南部地区则对流增强、降水偏多。第四模态降水异常呈现出“南北涝中间旱”的三极型分布特征,其原因是东亚中部地区高层出现异常东风,对流活动减弱,导致东亚中部降水偏少,而南部和北部地区降水偏多。

This study investigated the decadal relationship between the East Asian (EA) summer precipitation (EASP) and global sea surface temperature anomaly (SSTA) patterns. Maximum covariance analysis (MCA) was used to identify the coupling relationship between EASP and global SSTA. Four leading coupling modes were identified by MCA and they explained 27.7%,12.5%,8.9%,and 7.3% of the total variance, respectively. The spatial pattern of EASP of the first leading mode exhibited more-than-normal precipitation in most regions of EA. The second mode of EASP depicted a north-south “-+-” tripole pattern. The third one showed a “wet south and dry north” pattern, and the fourth mode exhibited a north-south “+-+” tripole pattern. The four coupling modes were suggested to be modulated by the global warming, Pacific Decadal Oscillation (PDO), Atlantic Multidecadal Oscillation (AMO), and North Pacific Gyre Oscillation (NPGO), respectively.The atmospheric processes and mechanisms underlying such modulations were also investigated. In the first coupling mode, global warming was favorable for increasing water vapor and precipitation over most parts of EA. In the second mode, PDO weakened the EA summer monsoon circulation, and it decreased precipitation in northern and southern EA regions and increased precipitation in the central EA region. The third mode was affected by AMO, which displaced the EA trough southward and weakened the convective activity over the northern EA region, thus leading to deficient precipitation in northern EA region. In the fourth mode, the EA summer monsoon was strengthened by NPGO, thus increasing precipitation in the northern and southern regions and decreasing precipitation in the central region.