热带西太平洋风应力异常在ENSO循环中作用的数值试验

利用一个中等复杂程度的海气耦合模式来研究热带西太平洋地区风应力异常对ENSO循环的影响,并以1997/1998年的El Nino事件为例,分析了模式结果中热带西太平洋地区风应力异常对El Nino事件形成影响的动力学及热力学作用.结果表明,热带西太平洋地区的风应力异常对ENSO循环有很重要的作用.在耦合模式中,当热带西太平洋地区的风应力异常由观测给定时,耦合模式基本上可以模拟出自1971年以来的EI Nino事件,观测与模拟的Nino 3区海面温度异常(SSTA)的相关系数可达0.63.赤道西太平洋地区的风应力异常可加强该地区大气的辐合,从而加强了大气的加热场,进而加强了海气相互作用的不稳定.赤道西太平洋地区西风异常激发出来的Kelvin波及水平平流对EI Nino事件初始阶段的发展起重要作用;海气相互作用及东边界的反射对EI Nino事件的发展及维持起重要作用.

A Numerical Test of the Effects of Wind Anomaly over the Equatorial Western Pacific on ENSO Cycle

Abstract An Intermediate Coupled Mode! (ICM) is used to study the effects of wind stress anomaly over the equatorial western Pacific on the ENSO cycle. The functions of dynamics and thermodynamics in which the wind anomaly stress over the equatorial western Pacific effects on the ENSO cycle are analyzed by taking the 1997 / 1998 El Nino event as an example. The results show that wind stress anomalies play an important role in ENSO cycle. In the ICM, when the wind anomaly stress over the equatorial western Pacific is given, the ICM can simulate almost all of the El NiRo events since 1971. The correlation coefficient is 0.63 between simulated and observed SSTA over the NiRo 3 area. The western wind stress anomaly over the equatorial western Pacific can strengthen the atmospheric heating field through reinforcing its convergence over there, then the instability of interactions between the atmosphere and the sea is strengthened. The Kelvin wave and horizontal advection exited by the western wind anomaly play an important role at the starting up and developing stage of El NiRo events. The interactions between atmosphere and sea and the eastern boundary reflection also play an important role in the developing and maintaining of El Nifio events.