东亚夏季风与北太平洋SSTA关系的年代际变化特征及其机制研究

摘要

Interdecadal features of east Asian monsoon and rainfall over north China and its relation with north Pacific SSTA are investigated by using NCEP/NCAR reanalysis data,SST data and Chinese station precipitation data.It's pointed out that east Asian summer monsoon varies obviously,with the precipitation in north China being abundant during strong east Asian summer monsoon phase before 1976,and the precipitation being deficient after 1976.Results also show that SSTA over north Pacific forces atmosphere mightily,which puts interannual scale “incitation” on interdecadal background field.A wavetrain is strengthened or weakened,by this way that SSTA over north Pacific connects with east Asian summer circulation,which causes the interannual variation of rainfall in north China with more precipitation before 1976,and v.v.after 1976.%利用NCEP/NCAR提供的40年再分析资料和英国气象局提供的海温资料以及中国气象局整编的160站降水资料,分析了东亚夏季风以及我国华北夏季降水的年代际变化特征及其与北太平洋SSTA的关系。指出东亚夏季风在70年代中期发生显著变化,1976年前东亚夏季风偏强,受其影响华北地区夏季降水偏多;1976年以后,东亚转为弱夏季风阶段,华北地区进入少雨期。研究表明,1976年前北太平洋SSTA对大气作用显著,北太平洋海温异常对大圆波列会产生一种年际尺度的“刺激”作用叠加在年代际背景上,加强或减弱波列强度,造成强夏季风阶段华北夏季降水偏多气候态下的年际变化。1976年后,北太平洋地区海气温差小,海温对大气加热作用不明显,因此北太平洋海温异常通过大圆波列与东亚夏季风的联系也变得淡漠,对我国华北地区夏季降水的影响不再显著。