Surface Features of Winter Monsoon Surges over South China

Abstract

The surface features associated with two kinds of winter monsoon surges over south China are studied: the easterly surge (ES) and the northerly surge (NS). Surface meteorological parameters over the region 15°?50°N, 90°?130°E for the surges that occurred in the three winters (October?March) from 1988 to 1991 are analyzed. For the northerly surge, the surface features found are 1) an abrupt temperature drop and wind direction turning from easterly to northerly, which can be related to the passage of a cold front; 2) an increase in the dewpoint depression; and 3) a large north?south pressure gradient. On the other hand, the easterly surge is found to be associated with strong easterly winds up to approximately 40 km h?1, little temperature or pressure change, and a southeastward motion of a high pressure center from Dahinggangling to the Yellow Sea together with a sharp pressure ridge along the east China coast. Furthermore, an ES and an NS are associated with different perturbations (anomalies) in pressure, wind, temperature, and dewpoint depression when compared with the wintertime normal condition. The results suggest a clear distinction between the two surges on the synoptic scale.