两类ENSO背景下中国东部夏季降水的环流特征及关键系统

利用全国160站逐月降水资料、74项环流指数、HadISST月平均海温资料以及NCEP/NCAR月平均再分析资料,对比分析了两类ENSO事件衰减阶段中国东部夏季降水及相应大气环流的差异,并探讨其可能成因。结果表明:1)EP型El Ni?o(La Ni?a)事件次年夏季,中国东部降水由北至南呈正负正(负正负)的三极型反相分布;CP型El Ni?o(La Ni?a)事件次年夏季,中国东部降水由北至南呈正负(负正)的偶极型反相分布;2)El Ni?o事件次年夏季,西北太平洋副热带高压(以下简称西太副高)及南亚高压均偏强,EP型西太副高偏西、南亚高压偏东,CP型西太副高范围更大、强度更强;La Ni?a事件次年夏季,西太副高及南亚高压强度偏弱,CP型强于EP型但弱于气候平均;3)El Ni?o事件期间西北太平洋上存在异常反气旋,EP型位置偏南,强度更强,持续时间更长,CP型位置偏北,范围更大;La Ni?a事件期间,西北太平洋区域至中国东南部存在异常气旋,EP型异常气旋的强度及范围均不及CP型;4)两类El Ni?o事件期间异常反气旋的差异可能与印度洋海盆增暖及太平洋海温持续性偏冷有关;两类La Ni?a事件期间异常气旋的差异可能由赤道西太平洋海温持续偏暖造成。

Circulation characteristics and critical systems of summer precipitation in eastern China under the background of two types of ENSO events

Based on the monthly precipitation data of 160 meteorological observation stations in China,the 74 circulation indexes,HadISST monthly mean sea surface temperature data and NCEP/NCAR monthly mean reanalysis data,this paper compared and analyzed the differences of summer rainfall in eastern China and related atmospheric circulation in the decaying stage of two types of ENSO events,and discussed the possible mechanisms.The results are as follows:(1) In the following summer of EP type of El Niño (La Niña) events,precipitation in eastern China presents a three-pole-type of "+-+" ("-+-") inverse distribution from north to south,while precipitation during the following summer of CP type of El Niño(La Niña) events in eastern China presents a dipole-type of "+-" ("+-") inverse distribution from north to south.(2) The western Pacific subtropical high (WPSH) and the South Asia high (SAH) in the following summer of El Niño events are much stronger than the climatological normal.WPSH (SAH) of EP El Niño moves further westward (eastward).The area of WPSH of CP El Niño is larger than that of EP El Niño,and the intensity is stronger as well.During the following summer of La Niña events,WPSH and SAH of CP La Niña are stronger than those of EP La Niña but weaker than the climatological normal.(3) An anomalous anticyclone exists in the northwestern Pacific during El Niño events.The anticyclone of EP El Niño is southward and stronger,and lasts longer than that of CP El Niño,while the anticyclone of CP El Niño is northward and has larger range.However,during La Niña events,an anomalous cyclone exists in the northwestern Pacific region to southeastern China.The anomalous cyclone of CP La Niña is much stronger,with the area much larger than that of EP La Niña.(4) The difference of northwestern Pacific anomalous anticyclone between the two types of El Niño events may be related to the warming of the Indian Ocean Basin and the persistent abnormal cooling of SST in the Pacific Ocean.The difference of northwestern Pacific anomalous cyclone between two types of La Niña events may be related to the persistent abnormal warming of SST in tropical western Pacific Ocean.