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

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 Niño3 index can be used to express the tropical Pacific sea surface temperature inter-annual anomalies. 11-year moving correlation coefficient of the Niño3 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.