Dynamical impact of anomalous East-Asian winter monsoon on zonal wind over the equatorial western Pacific

Abstract

Zonal wind anomaly over the equatorial western Pacific plays an important role in the occurrence of ENSO. The mechanism to produce zonal wind anomaly over the equatorial western Pacific is studied in this paper. It is shown clearly that zonal wind anomaly over the equatorial western Pacific is closely related to the anomaly of East-Asian winter monsoon. Anomalous strong (weak) East-Asian winter monsoon can excite not only the westerly (easterly) anomaly over the equatorial western Pacific but also a cyclonic (an anticyclonic) circulation over the east of the Philippines. The above anomalous circulation results from dynamical impacts of anomalous pressure pattern due to the East-Asian winter monsoon. Because there is westward (eastward) pressure gradient over the equatorial western Pacific, i.e. there is ∂p⧀v∂x 0), during strong (weak) East-Asian winter monsoon.