Interannual Fluctuations of the Tropical Monsoon Circulation Over the Greater WMONEX Area

Abstract

Synoptic analyses were conducted of interannual variations of the tropical winter monsoon circulation during the 20-year period from 1961 to 1980. The 150mb easterly wind at Singapore was used as an indicater of the strength of the tropical winter monsoon over the WMONEX area (South China Sea-Indonesia-northern Australia). Evidence has been shown that interannual fluctuations of the winter monsoon are deeply associated with the corresponding changes in the Walker circulation.
The monsoon was found to be strong when the sea level pressure was high near Tahiti and low near the Cocas Islands. The monsoon was weak when the opposite conditions were observed. The 1978-79 MONEX winter was one with a weak monsoon. There is a strong tendency for the formation of two ITCZs when the monsoon is strong. In comparison, only one ITCZ near New Guinea is observed during weak monsoon years.