陕西强连阴雨天气个例的综合分析

利用T213客观分析资料,对陕西2003年8月24日~9月7日强连阴雨天气过程的综合分析表明,连阴雨发生在欧亚稳定的环流形势下,乌拉尔山阻塞高压的建立和稳定使东亚中纬度纬向环流得以长时间维持。偏北、偏西、偏强的西太平洋副热带高压,不仅使冷空气受阻于秦岭山脉附近,同时其外围的偏南气流也为雨区提供了丰富的水汽,而乌拉尔山阻塞高压的崩溃引导冷空气大举南下,西太平洋副热带高压的东移南退则预示着持续的降水天气的结束。东亚合成环流的垂直结构表明,连阴雨期间秦岭邻近地区始终处于锋区中,并存在低空辐合、高空辐散的垂直结构。水汽条件分析表明连阴雨期间水汽的输送主要在对流层底部。热力学条件分析显示连阴雨期间河套始终为高潜热能区和位势不稳定区,偏南气流对热量的输送与高潜热能的维持有密切的关系,而低层偏东气流的加强促使了潜热能的释放,并导致了秦巴山区强降水天气的产生。

SYNTHETIC ANALYSES ON STRONG CONSECUTIVE RAINFALL IN AUTUMN OVER SHAANXI PROVINCE

Based on the objectively analyzed data of T213 model,the strong consecutive rainfall in Shaanxi province,which happened from August 24 to September 7,2003,has been analyzed.The results show that,this consecutive rainfall occurred in the stable zonal circulation of eastern Asian,with great longitudinal circles and blocked high at its upside,which made the latitudinal circle sustain in the mid-latitude areas of eastern Asian and west Pacific Ocean.The study on vertical structure of synthetic circle in eastern Asian displays that,during the consecutive rainfall,the area of Qinling Mountains was under the control of front,with vertical structure of convergence in the low air but divergence in high air.The vertical section displays rainfall progress happened with the flimsy cold air cushion in the low air,but warm air flow climbing by the cold air cushion.Additionally,the analyses on vapor condition explore that during the rainy time,the moisture was transported mainly in the bottom of troposphere and the water almost derived from the East Sea and the South Sea by the easterly or southerly great and stable airflow around the subtropical high.In the end,study of thermodynamics uncovers that Northwest China always was in the area of high potential,and the southerly airflow was closely related with the transmission of energy and the maintenance of high potential,at the same,time the strengthening of easterly air flow in the low air impelled the release of potential and resulted in the strong rainfall in Qinling Mountains.