山东省两次暴雪天气的对比分析

应用常规天气图资料、探空资料、加密自动站观测资料、地基GPS/MET遥感大气水汽观测资料、卫星云图、多普勒雷达观测资料和NCEP/NCAR 1。×1。再分析资料,采用诊断分析和对比分析方法,对山东省2009年11月11 12日和2010年2月28日两次暴雪天气的水汽、热力、动力条件和中尺度特征进行对比分析。结果表明,(1)两次暴雪都是受高空槽影响产生的,700hPa附近有较强的偏南气流向暴雪区输送暖湿空气,整层大气高湿近于饱和,中低层有逆温,整层温度≤0 C;暴雪产生在700～500 hPa槽前西南气流前部、850 hPa东北风与东南风辐合的区域,近地面层都为东北风。(2)不同点是,前次暴雪过程中低层先有冷空气影响,然后中高层暖湿气流北上,中低层能量低,以稳定性降雪为主,持续时间长;后次暴雪过程中,先是中低层暖湿气流北上,而后强冷空气从低层锲入,低层形成低涡,地面形成气旋,中低层对流不稳定,对流发展,降雪强度大,持续时间短。(3)暴雪期间GPS/MET水汽监测的可降水量在20 mm左右,对降雪量有一定的指示性。加密自动站观测中温度0C线是雨、雪的分界线,有助于判别降水的形态。

A Comparative Analysis of Two Snowstorms in Shandong Province

By using conventional weather chart data,sounding data,densified automatic weather station (AWS) data,ground-based GPS/MET remote sensing observation data of atmospheric water vapor,satellite cloud images,Doppler radar observations and the NCEP/NCAR 1°×1°reanalysis data,the water vapor, thermal and dynamic conditions and the mesoscale characteristics of two snow storms in Shandong Province during 11 to 12 November in 2009 and 28 February in 2010 were comparatively analyzed by using diagnostic methods.The results have shown:(1) The two snowstorms were caused by upper-level trough.There were warm and weter advection transported by stronger southwesterly flow at about 700 hPa.All atmospheric levels were near saturated.There were inversion temperatures in the middle-low level.The all level temperatures were less than 0℃.The snowstorm occurred in the front of southwest airflow in the 700—500 hPa trough and the converged region of the northeasterly and southeasterly at 850 hPa.Northeasterly winds were prevailing in the surface layer.(2) There were different characters in the two snowstorms.In the November 2009 snowstorm,there was the cold air influenced firstly then the warm and wet airflows run into middle-high levels,thus lower energy was stored in low levels,forming a stable heavy snow with longer duration.But in the February 2010 snowstorm,the warm and wet airflows inflowed firstly,then the cold air run into low levels.The vortex formed in low levels and cyclone came into being in the surface.There was convective instability in middle-low levels so that convection developed, a snowstorm with great snowfall intensity and short duration occurred.(3) In two snowstorms,the GPS/ MET precipitable water vapor were observations all about 20 mm,which can be an indicator for snowfall amount.The 0℃isolines of the temperatures observed by densified AWS were the boundary between rains and snows,which can help distinguish the precipitation forms.