冬/夏季热带太平洋与印度洋海表温度年际异常关系的年代际变化

The Inter-decadal Change of SSTA Interaction Between the Tropical Pacific and Indian Ocean in Winter/Summer

利用NCEP/NCAR再分析资料、全球海温海冰GISST 2.3b资料,用EOF技术分析了热带太平洋海表温度的年际异常(SSTA)变化特征表明:可用Ni^no3指数表示热带太平洋SSTA,并用该指数来讨论热带太平洋、热带印度洋SSTA间的关系。分季节分析表明:冬季Ni^no3指数与热带印度洋SSTA间的关系表现为热带印度洋整体相关系数为正的单极形态,且1976年以后两者的关系减弱,其原因是冬季为ENSO事件的盛期,另外,冬季西太平洋暖水区东移导致太平洋Walker环流上升支强盛处的东移,造成两洋的垂直纬向环流耦合减弱。夏季两者关系表现为偶极形态(热带西印度洋与Ni^no3指数同相变化,热带东印度洋则相反),但1976年以后两者的关系有所加强,是因为夏季为偶极子盛期,也是ENSO事件的发展期,同时夏季西太平洋暖水区东移并未引起太平洋Walker环流上升支强盛处的明显东移,且印度洋季风环流、太平洋Walker环流的上升支强盛处的强度增大了,造成两洋的垂直纬向环流耦合更强烈。即1976年以后,冬季热带两洋SSTA间的关系减弱了,而夏季两者关系则变得更密切。

The tropical Pacific sea surface temperature inter annual anomalies （SSTA） are analyzed in terms of NCEP/ NCAR reanalysis and GISST 2.3b datasets using EOF technique analysis, results show that the Nino3 index can be used to express the tropical Pacific sea surface temperature inter-annual anomalies. 11-year moving correlation coefficient of the Nifio3 index and the tropical Indian Ocean SSTA is used to reflect the relation between the tropical Pacific and the tropical Indian Ocean SSTA inter-decadal changing, because ENSO thrives in winter and Dipole thrives in summer, so its inter-decadal changing is studied in winter and summer. Results indicate that the difference of the moving correlation coefficients spatial distributions in two periods 1951-1976 and 1977- 2000 is dominant. In winter, the signal of ENSO is same over whole tropical Indian Ocean（moving correlation coefficients are positive from west to east）, during 1951-1976 period the intensity of correlation is stronger than the latter period, the possible reasons are as follows： firstly, the winter is the ENSO prime season, the second is in 1977-2000 period the warmer center of the tropical Pacific moves to east , then the Walker circulation updraft also moves eastwards, therefore the two vertical zonal circulations（the Walker circulation and the monsoon circulation） couple weakly. In summer the moving correlation coefficients spatial pattern differences from the winter spatial pattern, moving correlation coefficients are positive in the west tropical Indian Ocean, and moving correlation coefficients are negative in east tropical Indian Ocean, that is Dipole, but the gradient of the west tropical Indian Ocean moving correlation coefficient and the east tropical Indian Ocean moving correlation coefficient enlarges in the later period, the possible reasons are： Dipole thrives in summer, ENSO develops in summer, and the warmer center of the tropical Pacific moves eastwards in the later period, but the Walker circulation updraft moves to east slightly, and the intensity of the monsoon circulation and the Walker circulation updraft powerful place is strengthened, therefore the two vertical zonal circulations couple intensely. That is the inter-decadal variations of the interaction between the tropical Pacific and the tropical Indian Ocean SSTA are remarkable, in the different season, the inter-decadal variation tendency is not alike, it is mainly created by the tropical Pacific and the tropical Indian Ocean climate background field decadal oscillations.