2011年3月宁夏一次寒潮天气过程诊断

Diagnosis of a Cold Wave Weather Event in March 2011 in Ningxia

利用常规气象观测资料、NCEP/NCAR 1°×1°再分析资料等,采用天气动力学诊断方法,对2011年3月13～15日宁夏寒潮天气过程的影响系统配置、冷空气移动路径及高低空环流形势演变等进行诊断分析,并结合宁夏寒潮和大风沙尘预报指标,分析了强降温和大风沙尘的主要成因。结果表明:过程前期宁夏各地升温强烈,有强冷空气在西西伯利亚堆积并向南爆发造成此次寒潮天气;过程出现在乌拉尔山高压脊强烈发展东移过程中,影响系统为新疆快速东移短波槽与强锋区,促使寒潮爆发的流场为"低槽东移型",地面冷高压进入关键区,中心强度达1 062.7 hPa,以分裂南下方式影响;气温剧降的主要原因是850 hPa有强盛的冷平流自北向南控制宁夏;大风沙尘产生在强风区、辐合区、上升运动区及涡度梯度带上,并有"低层辐合中层辐散高层辐合"的垂直结构;由于系统浅薄、强度不强、宁夏及上游为平直西风气流、没有高空急流区配合是未出现沙尘暴的主要原因。在此基础上,提出宁夏春季寒潮预报概念模型和预报着眼点。

Based on conventional meteorological observation data and NCEP/NCAR reanalysis data,the diagnostic analysis was made about a cold wave weather event occurred from March 13 to 15 in 2011 in Ningxia,and the main reason of strong temperature drop,gale and sanddust weather were analyzed by combining with the cold wave prediction indexes of Ningxia.The results show that in early stage of the weather event,there was an obvious rising of temperature in Ningxia,and strong cold air accumulated in west Siberi and bursting toward south caused this cold wave event.During this cold wave process,the circulation over middle-high latitude Asia presented two troughs and one bridge,the dynamic mechanisms were upper rotating short-wave trough and strong front zone,the stream fields leading to outbreak of the cold wave were low trough moving east,the value of ground cold high pressure center reached to 1 062.7 hPa and it split and influenced Ningxia;After the burst of cold air,strong cold advection appeared over Ningxia,strong wind and dust occurred over the strong wind zone,convergence zone,vertical motion zone and vorticity gradient zone,and there was the vertical structure of convergence in lower level,divergence in middle level and convergence in high level,but there was no sandstorm occurred in Ningxia.Finally,we gave out the prediction conceptual model and forecast points of spring cold wave weather event in Ningxia.