江淮梅雨锋上典型中尺度对流涡旋诊断与模拟

发布时间：2019-02-13 00:55

【摘要】：2015年6月16日～17日江淮流域发生了一场持续性的暴雨。利用FY-2G卫星云顶相当黑体温度TBB资料和NCEP 1°×1°的再分析资料进行分析,发现此次降水强度与中尺度对流涡旋MCV(Meso-scale Convective Vortex简称MCV)的增强减弱以及西南急流强度一致,降水主要与MCV有关。这次MCV的形成与中尺度对流系统(Meso-scale Convective System简称MCS)的发生发展有着密切的关系。对流系统有组织的发展大量潜热释放以及低层辐合高层辐散的配置,触发MCV。对本次降雨中的MCV与MCS的关系和结构特征进行分析,表明:MCV从对流层低层一直伸展到对流层高层250 hPa,涡度最强中心在对流层中低层。MCS利于激发上升气流,湿Q矢量辐合中心与正涡度中心对应,利于热量和水汽的垂直输送,加速MCV发展。MCV从初生至成熟阶段,中低层的水平平流项基本为负贡献,水平辐合辐散项决定MCV的形成和发展。此外,垂直运动直接影响涡度垂直输送项,从而影响MCV在垂直方向上的发展。利用WRF模式对此次过程进行24小时的模拟,结果很好的再现了此次暴雨过程。利用模式输出的时空高分辨率资料,对这次暴雨过程中MCV各个阶段的结构以及温度收支进行分析。本次降雨在雷达上表现为一个典型的"人"字形回波,并与卫星云图上中两个中-β尺度的对流云团相对应。形成阶段MCV最显著的结构特征是:对流层高层不存在反环流,对流层底层西南气流与北边来的气流发生强烈辐合形成涡旋。MCV底层为冷池,MCV中层500hPa因潜热释放存在暖异常,无辐散层与垂直速度最大值均在550hPa上。MCV在成熟阶段的结构最显著的特征是:对流层高层200hPa存在反环流,暖中心依然在500hPa。对流系统周围存在两个次级环流,分别在南边的600-350hPa,和在北边700-550hPa。MCV在衰退阶段的结构:对流层低层辐合减弱但是依然存在,对流层中层没有明显的非绝热加热中心,对流层高层大气处在一种无序的湍流状态。通过对整个过程温度收支分析,发现MCV垂直温度结构为低空冷异常、高空暖异常,随着有组织的对流活动减弱,高空的暖异常逐渐减弱,最后只有低空的冷池依然维持。整个过程中微物理参数化方案和积云对流参数化方案对整层大气起加热作用,辐射作用在对流系统发展的前半段对大气主要起冷却作用,但是后半段对大气的温度的变化没有明显作用。
[Abstract]:From June 16 to 17, 2015, a persistent rainstorm occurred in the Jianghuai River Basin. Using the TBB data of the equivalent blackbody temperature on the top of the FY-2G satellite and the reanalysis data of NCEP 1 掳脳 1 掳, it is found that the intensity of the precipitation is consistent with the enhancement and weakening of the mesoscale convective vortex MCV (Meso-scale Convective Vortex for short MCV) and the intensity of the southwest jet. Precipitation is mainly related to MCV. The formation of MCV is closely related to the occurrence and development of mesoscale convective systems (Meso-scale Convective System MCS). The organized development of convection systems with a large amount of latent heat release and the configuration of low-level convergence and high-level divergence trigger MCV. The relationship and structural characteristics of MCV and MCS in this rainfall are analyzed. The results show that MCV extends from the lower troposphere to the upper troposphere with the strongest vorticity center at the middle and lower troposphere. MCS is helpful to stimulate updraft. The convergence center of wet Q vector corresponds to the center of positive vorticity, which is propitious to the vertical transport of heat and water vapor, and accelerates the development of MCV. The horizontal advection term of MCV is basically a negative contribution from the beginning to the mature stage. Horizontal convergence and divergence term determine the formation and development of MCV. In addition, vertical motion directly affects the vorticity vertical transport term, thus affecting the development of MCV in the vertical direction. The WRF model was used to simulate the process for 24 hours. The structure and temperature budget of MCV in each stage of the rainstorm were analyzed by using the spatio-temporal high resolution data from the model output. The rainfall shows a typical "human" zigzag echo on the radar and corresponds to two meso-尾-scale convective clouds in the satellite cloud image. The most significant structural characteristics of MCV in the formative stage are that there is no reverse circulation in the upper troposphere, strong convergence between the southwest and the north of the lower troposphere, and a cold pool at the bottom of MCV, and a warm anomaly in 500hPa in the middle of MCV due to latent heat release. The structure of MCV in mature stage is characterized by the existence of reverse circulation in the upper troposphere 200hPa, and the warm center is still at 500hPa. There are two secondary circulation around the convective system, 600-350 HPA in the south, and the structure of 700-550hPa.MCV in the north in the recession stage: the convergence of the lower troposphere weakens but still exists, and there is no obvious non-adiabatic heating center in the middle troposphere. The upper troposphere is in a turbulent state. Through the analysis of the temperature budget of the whole process, it is found that the vertical temperature structure of MCV is low altitude cold anomaly and upper air warm anomaly. With the decrease of organized convection activity, the upper air temperature anomaly weakens gradually, and only the low level cold pool is maintained. In the whole process, the microphysical parameterization scheme and cumulus convection parameterization scheme are used to heat the whole atmosphere, and radiation plays a major role in cooling the atmosphere in the first half of the development of the convection system. But the second half has no obvious effect on the temperature change of the atmosphere.
【学位授予单位】：华东师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P458.121.1

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