Interannual Variations in an Atmospheric GCM Forced by the 1970-1989 SST

[摘要] Interannual variations of the tropical atmosphere in a 20.5 year integration with an atmospheric general circulation model (GCM) forced by the observed near-global (40°S-60°N) sea surface temperatures from September 1969 to February 1990 are presented.Simulated interannual variations in the tropical Pacific related to El Nino/Southern Oscillation (ENSO) are comparable to the observations. An eastward-propagating signal which moves from the Indian Ocean to the central Pacific taking about one and a half year is clearly demonstrated by the 850mb tonal wind not only in the observed data but also in the simulated fields.The annual cycle and interannual variations of surface wind stresses over the tropical Pacific are investigated. The empirical orthogonal function (EOF) analysis of the zonal wind stress anomalies shows that the simulated first arid second EOF modes resemble the observed counterparts both in its spatial structure as well as the coefficient time-series. The eastward propagation of the zonal wind stress anomalies represented by these two modes has been reproduced by the GCM. The magnitude of the simulated zonal wind stress anomalies in the central Pacific is comparable to the observed counterpart. However, the model tends to show smaller zonal wind stresses over the western tropical Pacific during the development stage of ENSO. The magnitude of the simulated meridional wind stress over the equatorial Pacific is much smaller than the observation in its mean annual cycle as well as in its interannual variations, although its spatial structure arid time evolution is very similar to that observed.

[学科分类] 大气科学