2005年12月山东半岛暴雪成因及多尺度信息特征

Mechanism and Multi-scale Characteristics of Snowstorm Process Occurred in Shandong Peninsula in December 2005

利用常规天气资料、地面加密观测资料、卫星云图资料和多普勒雷达产品,对2005年12月山东半岛特大雪灾作了综合分析。研究表明,这次的冷流降雪归因于前期气温和海温偏高、冷空气势力偏强引起的海陆温差大、半岛北面临海的丘陵地形以及海岸锋等因素,地面自动站、雷达、卫星等多种尺度的特征信息清楚地揭示了其结构和演变。利用改进的简化伴随模式,对12月6日的烟台单站多普勒雷达资料进行了三维风场反演,结果表明,海陆热力差异和山脉对于向岸风的摩擦辐合作用形成了中尺度海岸锋,它引起了低层浅对流的产生。高空补充弱冷空气和降雪的潜热释放进一步激发了垂直上升运动,使对流活动发展加强,引起强降雪。当高空弱冷空气引起的系统性辐合上升运动与低层海岸线附近的海岸锋引起的中尺度辐合上升运动叠加时,降雪特别强烈。

Based on the meteorological observations,satellite image and Doppler radar data,the mechanism of snowstorm occurred in Shandong Peninsula in December 2005 is synthetically studied.Results show that the cold flow snowfall is attributed to the background of higher atmosphere temperature and sea surface temperature in the forepart,large temperature difference between ocean and land due to the stronger cold air,hilly landform north of Shandong Peninsula,and coast front.The multi-scale analyses of the surface weather auto-station,radar and satellite observations clearly reveal the structure and evolution of cold flow snowfall.The advanced simple adjoint method is adopted to retrieve the 3-D wind field of the snowstorm on 6 December 2005 from the single radar data of Yantai.It shows that the thermodynamic difference between sea and land and the friction between shoreward wind and mountain engenders the mesoscale coast front,which causes shallow convection in low layer.The weak cold air in upper levels and the latent heat released by the snow stir up the vertical ascending motion further,which leads to convective activity development and strengthening,so the heavy snowfall happens.When there is an overlap between the systemic convergence and updraft by the weak cold air in upper levels and the mesoscale convergence by the coast front in low layer,the snowfall is more violent.