Spatial And Temporal Characteristics Of Enso Oscillation As Well As Different Wind Stress Forcing Ocean Numerical Experiments

In this text we make a diagnosis of linear and nonlinear response of quasi-quadrennial (QQ) and quasi-biennial (QB) component of Nino3.4 index by using reanalyzed NCEP/NCAR data of SST, wind stress (Pseudo Stress) field, SSP, then have a time and spatial analysis of wind stress field by using MSSA, and finally find the importance and contrast the effect of different wind stress field forcing the sea so as to find the cause ofENSO irregularity. The result shows that (1) Quasi-quadrennial component of ENSO oscillation is most important form of all, and quasi-biennial one is the second important oscillation. (2) In the condition of quasi-quadrennial or quasi-biennial oscillation, monthly meananomaly fields of SLP, SSTA, x and f have the most important effect on thelinear response of Nino3.4, and there exists obvious spatial symmetry among cold and warm events of ENSO oscillation. (3) West wind stress anomaly and meridional wind stress anomaly occur in the east of tropic Pacific, which can boost the formation of EL Nino events. The stronger wind stress anomaly, the stronger the corresponding EL Nino event. When east wind stress anomaly and meridional wind stress anomaly happen the La Nina events occur. (4) Latitude and meridional wind stress fields both have the character of quasi-quadrennial and quasi-biennial oscillation, but their phases are different. So their conjunct effect makes ENSO oscillation have both quasi-quadrennial and quasi-biennial periodicity and erratic, which causes the forecast of ENSO events uncertainty. (5) The decadal variations of quasi-quadrennial and quasi-biennial components of wind stress fields make west wind anomaly of east Pacific and meridional wind stress anomaly converging upon the equator stronger since 1980s. The sea shows the same obvious decadal variation when responding to such wind stress. So the result showed above perhaps is one of the causes of that the EL Nino events are much particular, and their intensities become prevalently stronger, and the historical strongest EL Nino event occurs since the 1980s.