ENSO对中国沿海夏季降水影响的区域特征研究

Regional Impacts of ENSO on Summer Precipitation along the Chinese Coast

利用降水和海表温度格点数据以及中国沿海台站降水数据,分析中国沿海夏季降水对ENSO时空响应特点,并探讨中国沿海夏季降水年代际变化原因。结果表明:1)中国沿海夏季降水受ENSO影响区域特征明显,以连云港和云澳为界可分为3个区域。渤黄海沿海夏季降水与Niño3.4指数呈负相关,东海沿海呈正相关,南海沿海相关关系不显著。2)年代际尺度上,中国沿海夏季降水与Niño3.4指数关系不稳定。渤黄海沿海夏季降水与Niño3.4指数负相关在1980年之前和2010年之后较为显著,东海沿海的正相关在20世纪80年代之后变得不显著,南海沿海的相关关系不显著。3)年代际尺度上,渤黄海沿海夏季年代际降水与同期Niño3.4指数、前一年冬季AO指数和当年春季AAO指数呈显著负相关,而东海沿海都呈显著正相关,南海沿海夏季年代际降水与当年春季北极海冰指数呈明显负相关。对于Niño3.4指数,中东太平洋偏高的海表温度能在500hPa位势高度场激发出负太平洋-日本型遥相关波列,使得渤黄海沿海夏季年代际降水减少和东海沿海增多;当前一年冬季AO和当年春季AAO为正相位时,850 hPa风场在贝加尔湖南部的异常反气旋引导中高纬地区气流南下,引起东亚夏季风减弱,造成渤黄海沿海夏季年代际降水减少;另外,西北太平洋副热带高压强度偏强且位置偏西引起上升运动增强,导致东海沿海夏季年代际降水增多;春季北极海冰年代际变化能在850hPa风场和500hPa位势高度场上,激发出导致南海沿海夏季降水年代际变化相反的大气环流形势。

Rainfall and sea surface temperature grid data,as well as rainfall data from coastal stations in China,were used to obtain the spatiotemporal response characteristics of summer rainfall along the Chinese coast to ENSO and analyzed interdecadal changes in summer rainfall.The results show that:(1)Summer rainfall along the coast of China was significantly affected by ENSO and can be divided into three regions,with Lianyungang and Yunao as the boundaries.The Niño3.4 index was negatively correlated with summer rainfall along the Bohai and Yellow Sea coasts,positively correlated with that of the East China Sea coast,and not significantly correlated with that of the South China Sea coast.(2)On an interdecadal timescale,the relationship between summer rainfall along the coast of China and the Niño3.4 index was unstable.The negative correlation between summer rainfall along the Bohai and Yellow Sea coasts and the Niño3.4 index was significant before and after 1980 and 2010,respectively.The positive correlation along the East China Sea coast became insignificant after the 1980s,whereas the correlation along the South China Sea coast remained insignificant.(3)On the interdecadal timescale,the summer Niño3.4 index,winter Arctic Oscillation(AO)index in the previous year,and spring Antarctic Oscillation(AAO)index in current year were significantly negatively correlated with summer interdecadal rainfall along the Bohai and Yellow Sea coasts and positively correlated with summer interdecadal rainfall along the East China Sea coast.Summer interdecadal rainfall along the coast of the South China Sea was significantly negatively correlated with the spring Arctic Sea ice index in the current year.Regarding the Niño3.4 index,the high sea surface temperature in the Central and Eastern Pacific triggered a negative Pacific-Japan-type interconnection wave train in the 500 hPa geopotential height field,resulting in a decrease in interdecadal rainfall along the Bohai and Yellow Sea coast and an increase in interdecadal rainfall along the East China Sea coast.When the winter AO in the last year and spring AAO in the current year were in a positive phase,the abnormal anticyclone in the southern part of Baikal Lake at 850 hPa wind field guided the airflow in the mid to high latitudes southward,causing a weakening of the East Asian summer monsoon and a decrease in interdecadal summer rainfall along the Bohai and Yellow Sea.In addition,the strong,westward position of the subtropical high pressure in the northwest Pacific increases the upward movement,increasing interdecadal summer rainfall along the East China Sea coast.The interdecadal variation of spring Arctic Sea ice stimulates the opposite atmospheric circulation pattern that induced interdecadal variation of summer rainfall along the South China Sea coast in the 850 hPa wind and 500 hPa geopotential height fields.