A synoptic study of the northeastern monsoon over the South China Sea and its vicinity during December 1974.

Abstract

Through the study and evaluation of cold surges in the northeast monsoon, insight is gained into the relationship of the surges with large-scale mid-latitude and tropical systems, their horizontal and vertical structure, their equatorial penetration and their effects on other phenomena. The results lead to the tentative conclusions that due to the varying degree of air-sea interactions between cold air originating from the South China coast, the near-equatorial latitudes of the South China Sea will experience a freshening of the low-level northeasterly monsoon winds prior to a decrease in surface temperature which, if it occurs, is confined to the western portion of the South China Sea. This allows a near-equatorial disturbance (which may originate from the semi-stationary near-equatorial trough over the coast of northern Borneo or from a westward propagating wave in the western Pacific) to be intensified at an early stage of the surge by enhanced low-level convergence and organized deep cumulus convection. Afterwards it may be weakened by either cold incursion along the Vietnam coast or a slackening of the northeasterlies.