Structure of a cyclonic disturbance over the south China Sea and the Malaysian region during the winter monsoon

Abstract

In this paper, the results of a synoptic compositing technique to determine the structure of a cyclonic disturbance over the South China Sea during the winter monsoon are presented. The disturbance was confined to the lower troposphere. It intensified in the presence of cold surge. This indicates a strong lateral interaction between the extratropical westerly circulation and the equatorial disturbance. A calculation of meridional gradient of potential vorticity was carried out in the region of the disturbance, to test the existence of combined barotropic-baroclinic instability.