Numerical Simulation of 080125 Cold Air,Freezing Rain and Snow in Southern China
We simulate the low-temperature and freezing-rain/snow event in southern China during 25th-29th January 2008 by using the WRF model,and the results show that there appeared the coupling of lower and upper level jets over the middle and lower reaches of the Yangtze River and the area south of the river during the rain/snow episode;and the low level jet persistently transported warm/wet air towards the rain/snow area,where the low level moisture convergence promoted the occurrence and maintenance of large-scale rain/snow weather.The pumping effect of strong upper level divergence was conducive to the low level convergence,the ascending motion of the whole layer,and the maintenance of positive vorticity in the lower level.Cold air descended from the upper troposphere and moved southwards,enhancing the accumulation of convective unstable energy over the rain/snow area.The cold/dry air with high potential vorticity in the upper troposphere in the north side intruded along the dense HR contour zone into the lower layer of the rain/snow area,rapidly reinforcing the center of potential vorticity there.The close correspondence relation between potential vorticity and precipitation provides a better indicator for precipitation prediction.The stronger polar vortex allowed cold air to plunge southwards to southern China,the surface layer air of very low temperature froze rain water,resulting in the disaster of freezing rain in the episode.
cold airfreezing rain and snowWRF modeldiagnostic analysis
国家科技期刊平台
NSTL
万方数据
维普
