A STUDY OF THE THERMAL LOW OVER SOUTHWEST CHINA AND RELATED FORECASTING PROBLEMS.
EMMANUEL COLL BOSTON MASS ORIENTAL SCIENCE LIBRARY
Pagination or Media Count:
The thermal low which develops near the Szechwan basin is an important synoptic system exerting a pronounced influence on the weather over Southwest China in spring. The affected region is characterized by high temperatures, low humidity, fine weather with good visibility and a marked intensification of southerly winds. In addition, strong southerlies often prevail over western Kweichow and northern Yunnan. The dissipation of this type of thermal low usually brings precipitation and a fall of air temperature in the Szechwan-Kweichow region. The present study reveals the relationship between the thermal low and the upper vortex which appears at the 700-mb level over Southwest China above the thermal low prior to its maximum development. However, about 24-36 hours after its birth the 700-mb vortex usually moves eastward under the influence of a 500-mb trough in the upper westerlies, and the surface thermal low then begins to fill up. This paper summarizes the empirical rules governing the formation and development of the thermal low. Empirical predictors to forecast the growth and dissipation of the thermal low are derived from changes of meteorological elements at Kweiyang as plotted on synoptic charts. Author