兰州市2011年第一场透雨过程分析

Analysis of the First Soaking Rain Process in Lanzhou City in 2011

[目的]分析2011年兰州市第1场透雨过程。[方法]通过对2011年兰州市第1场透雨天气发生的天气尺度、中尺度及物理量诊断分析,探讨此次透雨天气的成因和物理量特征。[结果]高原低涡与西风带冷槽的结合是第1场透雨的影响系统,低层槽前700 hPa从四川盆地到河西有一条西南-东南向气流,俗称"倒扣风",为降水发生和持续提供了充沛的水汽;低层辐合、高层辐散有利于垂直运动;物理量分析和中尺度分析也证实了低层"倒扣风"的重要作用。[结论]该研究为春季久旱转雨的实时预报业务提供参考。

[Objective] The research aimed to analyze the first soaking rain process in Lanzhou in 2011.[Method] By diagnosis analyses on weather scale,meso scale and physical quantity when the first soaking rain weather happened in Lanzhou City in 2011,formation reason and physical quantity characteristics of the soaking rain weather were discussed.[Result] Combination of the plateau low vortex and westerly cold trough was influence system of the first soaking rain.There was a southwest-southeast airflow from Sichuan Basin to Hexi in front of the trough at 700 hPa.It was commonly referred to as ＂reversing wind＂,and provided sufficient water vapour for occurrence and maintaining of the precipitation.Convergence at the low layer and divergence at the high layer were favourable for vertical motion.Analyses on physical quantity and meso scale also proved important role of the ＂reversing wind＂ at the low layer.[Conclusion] The research provided reference for real-time forecast business of the long drought turning rain in spring.