The data analyses in the first part of this study have shown that the sea surface temperature anomalies (SSTA) in the eastern equatorial Pacific are significantly correlated with the preceding anomalous convergenee of the meridional wind stress near the equator. In order to understand the dynamical role of the convergent meridional wind stress anomalies in the El Ni o occurring, an ideal wind stress which converges about the equator is set up based on the observations revea1ed in the first part. A simp1e dynamical model of tropical oeean is used to study the response of the tropical ocean to the convergent meridional wind stress. The results show that the convergent wind stress in the eastern equatorial Pacific is favorable for the occur- rence of El Ni o. When the convergent wind stress exerts on the tropical oeean, the westward propagating Rossby wave is excited, which, on the one hand, makes the mixed layer near the equator become thicker. On the other hand, the westward oceanic currents associated with the Rossby wave appear in the vicinity of the equator. The oceanic currents can drive the upper layer sea water to transfer to the west, which is favorable for the sea water to pile up in the western equatorial Pacific and to accumulate energy for the upcoming warm event.
