黄土高原一次引发短时致洪暴雨MCC的特点及成因

利用MICAPS资料、多普勒天气雷达资料和NCEP资料等,对2013年7月25日黄土高原一次引发短时致洪暴雨MCC的特点及成因进行了分析。结果表明:300hPa天气尺度反气旋和500hPa天气尺度西南气流是MCC在对流层中上层的直接影响系统,700hPa α-中尺度横切变和850hPa副热带高压西侧α-中尺度低涡是MCC在对流层低层的直接影响系统;地面湿焓场低值舌的活动是MCC触发机制之一;地面湿焓场≥40℃高值中心区和MCC生成区相对应;MCC生成区在径向速度场上出现西南低空急流的生成和维持、逆风辐合区的生成和维持,低层辐合和高层强辐散的配置,为MCC的生成及暴雨的形成提供了动力条件;冷暖平流的配置也为MCC生成和东移发展创造了有利条件;空间剖面图上看到的湿螺旋度高值带对MCC生成发展和东移具有指示意义。 

Characteristics and Causes of the MCC in a Short Time Flooding Rainstorm in Loess Plateau

MICAPS data,Doppler radar data and NCEP data,etc.,were used to analysis characteristics and causes of the MCC in a short time flooding rainstorm occurred on July 25,2013 in the Loess Plateau. The results showed that: 300hPa synoptic scale anticyclonic,500hPa synoptic scale southwesterly airstream is direct weather influence system of the MCC in the upper-middle troposphere,700hPa α- mesoscale transversal shear and 850hPa α- mesoscale low vortex on the west side of subtropical high is direct weather influence system of the MCC in the lower troposphere; the low-value tongue of moist enthalpy field at surface is one of the trigger mechanism of MCC; the high value center of moist enthalpy field which is greater than or equal to 40 ℃ corresponding to the MCC generating area; the formation and maintenance of southwest low level jet,the generating and maintaining of adverse wind convergence region,with low-level convergence and high level strong divergence configuration appeared on the radial velocity field in MCC generating area provide dynamical condition for the generation of MCC and formation of the heavy rain; the space allocation of cold and warm advection created favorable conditions for the generation and eastward development of MCC; the high-value zone of moist helicity in space cross- section diagram has indicative significance for the generation,development and eastward movement of MCC.