影响广西的三次寒潮过程对比研究

Comparative analysis of three cold wave processes in Guangxi

利用NCEP资料、常规地面资料、探空资料对2008—2009年影响广西的三次寒潮过程的强度、影响以及水汽、动力、热力机制进行对比分析。研究表明:寒潮的强弱与极涡偏心于东亚的早晚和倒Ω流型有关。500 hPa横槽转竖造成的降温比横槽南压和小槽东移更强烈。导致2008年12月寒潮天气的500 hPa形势为横槽转竖型,出现雨夹雪天气,但天气较快转晴;导致2008年1月寒潮过程的500 hPa形势为横槽南压型,寒潮过后依然有冷空气不断补充,带来长期的低温冰冻天气;2009年2月寒潮过程为小槽东移型,尽管降温不强,但由于南支槽发展,水汽供应充分,导致长期的阴雨天气。ω方程分析表明:2008年12月寒潮雨夹雪过程上升运动主要由500与850 hPa正涡度差引起,2009年2月寒潮小雨过程,上升运动主要由850 hPa暖平流上升运动引起。

Based on the NCEP,routine surface observation and sounding data,three cold waves occurred in 2008—2009 in Guangxi are comparatively analysed in respect to intensity,influence,vapor,dynamic and thermodynamic mechanism.The results show that the cold waves intensity is related to the later or sooner appearance of polar vertex which is off-center against East Asia and the inverted Ω flow pattern.The temperature decrease caused by the 500 hPa horizontal trough turning to longitudinal style was more intense than that caused by the horizontal trough moving southward style and the small trough moving eastward.The cold wave in December of 2008 belonged to the 500 hPa horizontal trough turning to longitudinal,sleeting appeared,but it turned clear quickly.The cold wave in January of 2008 belonged to the horizontal trough moving southward.After the cold wave there still were cold air supply to the south,so it led to long term low temperature and frost weather.The cold wave in February of 2009 belonged to the small trough moving eastward.Even through the temperature decrease wasn＇t stronger than the others,but the Indian-Myanmar trough developed,the water vapor supply was enough to sustain long term raining weather.The quasi-geostrophic Omega equation analysis showed that the upward vertical motion of the cold wave with sheeting in December of 2008 was caused by the positive differential vorticity advection between 500 hPa and 850 hPa.The upward vertical motion of the cold wave with raining in February of 2009 was caused by the 850hPa warm advection moving upward.