A Numerical Test of the Effects of Wind Anomaly overthe Equatorial western Pacific on ENSO Cycle
Yan Bangliang(Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100080)Zhang Renhe(Chinese Academy of Meteorological Sciences, Beijing 100081)
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.