Study on Numerical Simulation of the Strong Gale of Cold Wave in Dalian Area

LI Yan et al(Dalian Meterological Bureau,Dalian,Liaoning 116001)

Strong gale of the cold wave;Cold front;Jianghuai cyclone;Cold air;Numerical simulation

According to conventional data and automatic weather station data,the extreme cold-windy weather in Dalian Area from March 4th to 5th in 2007 were analyzed by the mesoscale numerical model(MM5V3).The results showed that the extreme cold-windy weather was caused by the interaction between strong cold front due to cold air from the north to the southeast and strong Jianghuai cyclone which moved to the north.By the action of sinking airflow,strong cold air was accumulated in the middle and low level in the upstream region of Dalian,and formed a strong cold and dry center.There was a strong negative vorticity and strong divergence in the low level,a strong positive vorticity and strong convergence in the high level.This situation was conducive to strengthening surface cold high and cold front.In the eastern part of Dalian,there was a strong positive vorticity and strong convergence in the low level,a strong negative vorticity and strong divergence in the high level.This situation was conducive to enhancing the development of cyclone.There was a strong high pressure in the west side and an exceptionally strong cyclone in the east side from the ground surface to the altitude of 850 hPa.This situation was very favorable to form the strong gale of the cold wave.From west to east through Dalian region,the strong pressure gradient resulted in the rare gale weather of the cold wave in Dalian.