中国东部2012年夏季降水及年代际转型的可能信号分析

针对2012年夏季中国东部降水"南旱北涝"的异常特征, 对比分析了近50年不同年代中国东部降水的分布型及海洋和环流等影响因素, 并讨论了2012年中国东部夏季降水异常作为中国东部降水年代际转型信号的可能性. 研究结果表明: 1961—1978年期间, 北太平洋年代际涛动(PDO)处于冷位相, 东亚夏季风偏强, 西太平洋副热带高压(副高)偏弱, 北方地区冷空气活动偏弱, 从而有利于南方水汽北上, 造成中国北方地区夏季降水异常偏多; 1979—1992年间则呈相反的特征, 造成1970年代末期中国东部夏季降水发生了一次年代际尺度的调整. 2010年代后期以来, PDO由暖位相向冷位向转变, 2012年北太平洋海温异常偏暖, 西太平洋海温由异常偏暖状态转变为正常略偏冷状态, 东亚夏季风由弱变强, 副高由强变弱, 北方冷系统活动减弱, 这些特征均与1961—1978年时段的情况类似, 支持2012年作为中国东部夏季降水发生年代际调整的前期信号的可能性. 近10年PDO, 东亚夏季风(EASM), 副高(WPSH)和贝湖高压(BH)四种指数夏季平均值的演变则进一步说明 了2012年的这种异常特征不仅是年际尺度的振荡, 更可能是前期演化基础上的一种量变到质变的调整. 关键词： 年代际 降水 北太平洋年代际涛动 东亚夏季风

Analysis of the summer precipitation of 2012 in East China and its possibility of decadal shift

Considering the abnormal precipitation in north-west and drougtin south China during the summer of 2012, we have analyzed the decadal precipitation distribution and the chief probably-influencing factors in recent 50 years, in order to make a discussion of the possibility of decadal change of summer precipitation in East China since the summer of 2012. Research results show that the north Pacific decadal oscillation (PDO) is in cold phase, and the north cold air active and the west Pacific subtropical high (WPSH) are both in weak phase during the summer of 1961-1978. This situation is beneficial to the strong east Asia summer monsoon (EASM) and the north expansion of the low latitude water vapor, causing the summer precipitation in northern China more than normal in this decadal. While the situation is in quite opposite way during 1979-1992 (which causes the decadal change of summer precipitation in east China) that the precipitation is less than normal in northern China during the late period. Meanwhile, since in the late 2010 PDO changed from the warm phase to cold phase, the sea surface temperature was warmer in north Pacific and colder in west Pacific than normal, while the west Pacific subtropical high and the north region cold air active both changed from strong phase to weak phase, and the EASM became stronger, quite similar to that in 1961-1978. All of the cases showed that there might be once more a decadal change of summer precipitation in East China since the summer of 2012. Furthermore, the yearly variation of indices of PDO, EASM, WPSH and Baikal Height (BH) showed that the abnormal precipitation distribution and the chief influencing factors are not only the yearly variables but also the probable signal of decadal change in the following years.
Keywords： decadal variation precipitation north Pacific decadal oscillation east Asia summer monsoon