A CASE STUDY OF THE STRUCTURE OF THE HETAO HIGH WHICH CAUSED LONG-LASTING HOT WEATHER IN BEIJING

Based on the severe hot weather case taken place on July 11—14, 2000 in Beijing, we analyzed the horizontal and vertical structure of the Hetao High on 700 hPa associated with the hot weather. The result shows that the High is a deep negative vorticity system and related with a large-scale, eastward moving warm air mass in western arid region. The Hetao High is a relatively small and locomotive system, so hot weather usually sustains only several days. As a warm high, the Hetao High reached the high level of troposphere in vertical direction. Located between the exit region of Polar-front jet and the entrance region of subtropical jet, the upper level convergence makes Hetao High under the control of downward current. Adiabatic warming because of sinking and radiation heating are in favor of hot weather. At last, the paper pointed out that the formation of the Hetao High might be associated with dynamically pressure increase.