RELATIONSHIP BETWEEN THE VARIATION IN HORIZONTAL VORTICITY AND HEAVY RAIN DURING THE PROCESS OF MCC TURNING INTO BANDED MCSS  

作　　者：丁治英 高松 常越 

机构地区：[1]Key Laboratory of Meteorological Disaster,Ministry of Education/Joint International Research Laboratory of Climate and Environment Change/Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters,N anjing University of Information Science and Technology,Nanjing 210044 China [2]Chongqing Institute of Meteorological Sciences,Chongqing 401147 China [3]Guangzhou Meteorological Bureau,Guangzhou 510080 China

出　　处：《Journal of Tropical Meteorology》2016年第2期220-232,共13页热带气象学报（英文版）

基　　金：National Program on Basic Research Project(973 Program)(2009CB421503,2013CB430103);National Natural Science Foundation of China(40975037);Construction of Advantageous Disciplines for Higher Education in Jiangsu Province,Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)

摘　　要：Using real-time data and the WRF mesoscale model,a heavy rain event in the process of Mesoscale Convective Complex(MCC) turning into banded Mesoscale Convective Systems(MCSs) during 18-19 June 2010 is simulated and analyzed in this paper.The results indicated that the formation and maintenance of a southwest vortex and shear line at 850 h Pa was the mesoscale system that affected the production of this heavy rain.The low-vortex heavy rain mainly happened in the development stage of MCC,and the circular MCC turned into banded MCSs in the late stage with mainly shear line precipitation.In the vicinity of rainfall area,the intense horizontal vorticity due to the vertical shear of u and v caused the rotation,and in correspondence,the ascending branch of the vertical circulation triggered the formation of heavy rain.The different distributions of u and v in the vertical direction produced varying vertical circulations.The horizontal vorticity near the low-vortex and shear line had obvious differences which led to varying reasons for heavy rain formation.The low-vortex heavy rain was mainly caused by the vertical shear of v,and the shear line rainfall formed owing to the vertical shear of both u and v.In this process,the vertical shear of v constituted the EW-trending rain band along the shear line,and the latitudinal non-uniformity of the vertical shear in u caused the vertical motion,which was closely related to the generation and development of MCSs at the shear line and the formation of multiple rain clusters.There was also a similar difference in the positively-tilting term(conversion from horizontal vorticity to vertical positive vorticity) near the rainfall center between the low-vortex and the shear line.The conversion in the low vortex was mainly determined by бv/бp<0,while that of the shear line by бu/бp<0.The scale of the conversion from the horizontal vorticity to vertical vorticity was relatively small,and it was easily ignored in the averaged state.The twisting term was mainly conducive to the reinforUsing real-time data and the WRF mesoscale model,a heavy rain event in the process of Mesoscale Convective Complex（MCC） turning into banded Mesoscale Convective Systems（MCSs） during 18-19 June 2010 is simulated and analyzed in this paper.The results indicated that the formation and maintenance of a southwest vortex and shear line at 850 h Pa was the mesoscale system that affected the production of this heavy rain.The low-vortex heavy rain mainly happened in the development stage of MCC,and the circular MCC turned into banded MCSs in the late stage with mainly shear line precipitation.In the vicinity of rainfall area,the intense horizontal vorticity due to the vertical shear of u and v caused the rotation,and in correspondence,the ascending branch of the vertical circulation triggered the formation of heavy rain.The different distributions of u and v in the vertical direction produced varying vertical circulations.The horizontal vorticity near the low-vortex and shear line had obvious differences which led to varying reasons for heavy rain formation.The low-vortex heavy rain was mainly caused by the vertical shear of v,and the shear line rainfall formed owing to the vertical shear of both u and v.In this process,the vertical shear of v constituted the EW-trending rain band along the shear line,and the latitudinal non-uniformity of the vertical shear in u caused the vertical motion,which was closely related to the generation and development of MCSs at the shear line and the formation of multiple rain clusters.There was also a similar difference in the positively-tilting term（conversion from horizontal vorticity to vertical positive vorticity） near the rainfall center between the low-vortex and the shear line.The conversion in the low vortex was mainly determined by бv/бp〈0,while that of the shear line by бu/бp〈0.The scale of the conversion from the horizontal vorticity to vertical vorticity was relatively small,and it was easily ignored in the averaged state.The twisting term was mainly conduciv

关 键 词：heavy rain Mesoscale Convective Systems(MCSs) numerical simulation horizontal vorticity twisting term 

分 类 号：P445[天文地球—大气科学及气象学]