Diagnosis And Simulation Of A Typical Mesoscale Convective Vortex Over The Meiyu Front

Based on the black body temperature at cloud top data of FY-2G and reanalysis data,the sustained heavy rain in Yangtze-Huaihe river basin during 16—17 June 2015 was analyzed.Analysis showed:The intensity of the precipitation was essentially consistent with the evolution of mesoscale convective vortex(MCV)and the southwest jet.MCV was triggered by latent heat induced by the organized development of convection and the low level convergence and upper level divergence.NCEP reanalysis data were employed to diagnose the structural characteristics of MCV and the relationship between MCV and MCS.It could be found the MCV positive vorticity region extended from the lower troposphere to 250 hPa.During the mature stage,MCS could help to stimulate updraft and was benefit to transport heat and water vapor because the convergence zone of wet Q vector corresponded to the center of positive vorticity,which promoted the development of MCV.At the same time,the upper divergence and the lower convergence further accelerated the development of MCS.The positive vorticity moved downwards along with the downwards motion of convergence which mainly inspired and developed MCV and the horizontal advection contributes negative to the vorticity during the whole stage.Ascending motion of the vortex had a direct impact on the vertical transportation of vorticity and further influenced on the development of the vortex in the vertical.The WRF model was used to simulate the heavy rain process and the simulated results showed the development of mesoscale rainstorm system is well described.By analyzing the high spatial and temporal model data,the structure and the temperature budget are analyzed during each stage of MCV.The rainfall is a typical herringbone echo corresponding to the two meso-beta convective cloud clusters in the satellite image.The structural characteristics of MCV in the formative stage:there is no mesoscale anticyclonic circulation in the upper layer and a cool pool at the lower troposphere.The low southwestly jet strongly converged with the northerly flow near vortex center at the low level.There is a warm anomaly in 500hPa due to the latent heat release?The non-divergence level and the max value of vertical velocity are both in 550hPa.The structural characteristics of MCV in the mature stage:there is a mesoscale anticyclonic circulation in the upper layer,and the warm anomaly center is still in 500hPa.The bottom of the MCV is still a strong convergence of the southwest airflow and the north flow.There are two secondary circulations in the south of the 600-350hPa and in the north of 700-550hPa respectively.The structural characteristics of MCV in the decay stage:The convergence is weakened but still existed in the lower troposphere.There is no obvious diabatic heating center in the middle troposphere.The high-level atmosphere was in a disordered state of turbulence.According to the analysis of the temperature budget,it's found that the vertical temperature structure of MCV is a cold anomaly at lower level and a warm anomaly at high level.With the decrease of organized convection,the warm anomaly at high level is gradually weakened.But the cool pool still existed at the lower layer.The microphysical parameterization schemes and the cumulus convection parameterization schemes heated the atmosphere during all the stage.Radiation have a cooling effect on the atmosphere during the first half,but it did not play any role during the second half.