辽宁地区暴雨强对流天气的数值模拟与诊断分析

【作者】 王健；

【导师】 寿绍文；

【作者基本信息】 南京信息工程大学 ， 气象学， 2005， 硕士

【摘要】 本文对2003年8月5日—6日发生在辽宁地区的一次暴雨过程进行了研究。在对大尺度天气形势和多普勒雷达资料进行分析后,确定此次暴雨过程的主要影响系统是华北气旋。中纬度短波槽的发展引导贝湖冷空气南下、副高稳定与加强以及低空急流输送大量暖湿气流是华北气旋生成的重要条件;高空前倾槽的结构加大了大气的垂直不稳定,是引起强对流天气的重要原因。雷达回波具有混合型特征,而速度场零速度线对气旋生成与发展有很好表征。 为进一步揭示出此次华北气旋生成及发展的原因,本文应用中尺度模式MM5对此次暴雨过程进行了数值模拟。经降水量对比,认为模拟效果较好。利用模式输出的时空较密的资料作诊断分析,研究了辽宁地区的强对流系统的发生发展规律。结果表明:(1)“干侵入”使低空正位涡增大,气旋性环流加强,这是此次华北气旋生成后迅速发展加强的重要原因之一。位涡柱对地面气旋与高空槽的发展有较好的指示性,位涡柱形成时刻前后降水达到最强;(2)高空切变线上存在的中尺度环流是这次暴雨的直接影响因子之一,而与强烈发展的低空急流相伴的次级环流的上升支是暴雨的触发机制。强降水发生在Q矢量辐合区和辐散区的交界处;(3)总螺旋度的分布和强降水及其时间演变具有较好的对应关系。总螺旋度大值区对应着强降水区;总螺旋度中心值达到极大的时间要比强降水发生时间早2—3小时。螺旋度与低空急流有较好的对应关系,其大值区中心位置及强度变化与低空急流是一致的。更多还原

【Abstract】 A heavy rain process occurred in Liaoning area during Aug. 5-6, 2003 is studied in this paper. Based on synoptic maps and radar data analysises, the north-China cyclone is regarded as the major influnce synoptic system for the heavy rain process. The short wave trough development caused the cold air moved southward, and the stationary subtropical high, as well as the low level jetstream carrying warm and moist air are the important factors for the cycloginisis and development of the north-China cyclone. The structure of the forward-tilted trough increases the atmospheric instability and caused the severe convective weather. Radar echoes are in mixing type. The zero velocity isoline well indicates the formation and development of the cyclone.For further investigating the causes of the cyclone development, a numerical simulation by using MM5 and a diagnostic analysis based on the outputs of the model have been done. The results showed that, the dry intrusion causes the cyclone increase;the secondary circulation plays a role of trigger mechanism; and the helicity distribution well corresponding to the precipitation.更多还原