一次江淮地区MCV过程的数值模拟分析
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摘要
本文在前期统计工作的基础上,选取了一次典型的中尺度对流涡旋(MCV)个例,利用NCEP/NCAR再分析资料分析其背景场特征,并利用WRF数值模拟结果分析其成因及其触发"二次对流"的可能机制。结果表明:MCV发生前,江淮地区处于200 h Pa强辐散场中,高层抽吸作用明显,500 h Pa江淮西北部短波槽槽后不断有冷空气南下,加强该地区大气层结不稳定,850 h Pa湖北至安徽中部有切变线活动,这种高低层配置十分有利于MCV生成及对流发生;MCV生命史各阶段垂直输送项和涡管倾斜项呈反位相分布,而水平平流项和辐合辐散项的作用基本是相互抵消的,垂直输送项和辐合辐散项是MCV生成阶段中低层涡度的主要来源;MCV引发的"二次对流"出现在其生成阶段,且位于其南侧,MCV发展成熟后,对流迅速减弱;MCV的生成使南侧西南低空急流加强,伴随水平涡度的变化,"二次对流"的发生发展与水平涡度对应的垂直环流上升支有直接联系。
Based on the previous statistical analysis,a typical Mesoscale Convective Vortex( MCV)case was selected to investigate its background situation,possible causes and vertical structures by using NCEP/NCAR global objective analysis and WRF simulation data. Results indicate that before MCV forms,Yangtze-Huaihe Basin is in the position with strong divergence at 200 h Pa,and dry cold air invasion increases potential instability of atmosphere structure. The shear line is active from Hubei to the center of Anhui Province,which is of great importance to the generation of MCV and new convection. The contributions from vertical advection and tilting counteract at different levels during each stage of MCV lifetime while that from horizontal advection and convergence is opposite. The major vorticity in low layer during the development stage of MCV comes from vertical advection and convergence as a whole. The secondary convection is located on the southern part of MCV center and mainly occurs during the development stage of MCV. After the formation of MCV,the southwesterly airstream in its southern part enhances the jet in the lower level,which may contribute to the change of horizontal vorticity result from vertical wind shear and then lead to updrafts. The two updrafts caused by different low level jets together providedynamic conditions for the secondary convection.
Based on the previous statistical analysis,a typical Mesoscale Convective Vortex( MCV)case was selected to investigate its background situation,possible causes and vertical structures by using NCEP/NCAR global objective analysis and WRF simulation data. Results indicate that before MCV forms,Yangtze-Huaihe Basin is in the position with strong divergence at 200 h Pa,and dry cold air invasion increases potential instability of atmosphere structure. The shear line is active from Hubei to the center of Anhui Province,which is of great importance to the generation of MCV and new convection. The contributions from vertical advection and tilting counteract at different levels during each stage of MCV lifetime while that from horizontal advection and convergence is opposite. The major vorticity in low layer during the development stage of MCV comes from vertical advection and convergence as a whole. The secondary convection is located on the southern part of MCV center and mainly occurs during the development stage of MCV. After the formation of MCV,the southwesterly airstream in its southern part enhances the jet in the lower level,which may contribute to the change of horizontal vorticity result from vertical wind shear and then lead to updrafts. The two updrafts caused by different low level jets together providedynamic conditions for the secondary convection.
引文
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[2]Bartels D L,Maddox R A.Midlevel cyclonic vortices generated by mesoseale convective systems.Mon.Wea.Rev.,1991,119(1):104-118.
[3]Trier S B,Davis C A,Tuttle J D.Long-lived mesoconvective vortices and their environment.Part I:Observations from the central United States during the 1998 warm season.Mon.Wea.Rev.,2000,128(10):3376-3395.
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[7]王金鑫,潘益农,束宇,等.中尺度对流涡旋(MCV)近30 a来的研究进展.气象科学,2014,34(3):343-354.WANG Jinxin,PAN Yinong,SHU Yu,et al.Advance in research on MCV in recent thirty years.Journal of the Meteorological Sciences(in Chinese),2014,34(3):343-354.
[8]王微,潘益农,束宇.中国东部夏季中尺度对流系统以及中尺度对流涡旋的特征.南京大学学报(自然科学),2011,47(6):692-702.WANG Wei,PAN Yinong,SHU Yu.The characteristics of mesoscale convective system and mesoscale convective vortex in summers over eastern China.Journal of Nanjing University(Natural Sciences)(in Chinese),2011,47(6):692-702.
[9]朱爱军,潘益农.中国东部地区一个中尺度对流涡旋的涡度收支分析.南京大学学报(自然科学),2007,43(3):260-269.ZHU Aijun,PAN Yinong.A vorticity budget for a mesoscale convective vortex over East China.Journal of Nanjing University(Natural Sciences)(in Chinese),2007,43(3):260-269.
[10]张元春,孙建华,徐广阔,等.江淮流域两次中尺度对流涡旋的结构特征研究.气候与环境研究,2013,18(3):271-287.ZHANG Yuanchun,SUN Jianhua,XU Guangkuo,et al.Analysis on the structure of two mesoscale convective vortices over YangtzeHuaihe River basin.Climatic and Environmental Research(in Chinese),2013,18(3):271-287.
[11]刘瑞翔,丁治英,王一颉.2007—2013年夏季江淮地区MCS和MCV与暴雨关系的统计特征.气象科学,2016,36(2):236-243.LIU Ruixiang,DING Zhiying,WANG Yijie.Statistical characteristics of relations of rainstorms with MCSs and MCVs in YangtzeHuaihe Basin during summer from 2007 to 2013.Journal of the Meteorological Sciences(in Chinese),2016,36(2):236-243.
[12]王晓芳,汪小康,徐桂荣.2010年长江中游梅雨期β中尺度系统环境特征的分析.高原气象,2013,32(3):750-761.WANG Xiaofang,WANG Xiaokang,XU Guirong.Analysis on environment of meso-β-scale system of continuous heavy rainstorm over the middle reach of Yangtze River during Meiyu period in 2010.Plateau Meteorology(in Chinese),2013,32(3):750-761.
[13]李慧,周顺武,王亚非,等.2010年梅雨期间我国东部地区降水异常的成因.南京信息工程大学学报(自然科学版),2014,6(6):549-557.LI Hui,ZHOU Shunwu,WANG Yafei,et al.Analysis of precipitation anomalies in the middle and lower reaches of the Yangtze River during June-July of 2010.Journal of Nanjing University of Information Science and Technology(Natural Science Edition)(in Chinese),2014,6(6):549-557.
[14]丁治英,高松,常越.MCC转为带状MCSs过程中水平涡度的变化与暴雨的关系.热带气象学报,2013,29(4):540-550.DING Zhiying,GAO Song,CHANG Yue.Relationship between the variation of horizontal vorticity and heavy rain in the process of MCC turning into banded MCSs.Journal of Tropical Meteorology(in Chinese),2013,29(4):540-550.
[2]Bartels D L,Maddox R A.Midlevel cyclonic vortices generated by mesoseale convective systems.Mon.Wea.Rev.,1991,119(1):104-118.
[3]Trier S B,Davis C A,Tuttle J D.Long-lived mesoconvective vortices and their environment.Part I:Observations from the central United States during the 1998 warm season.Mon.Wea.Rev.,2000,128(10):3376-3395.
[4]ZHANG Dalin,Fritsch J M.A numerical investigation of a convectively generated,inertially stable,extratropical warm-core mesovortex over land.Part I:Structure and evolution.Mon.Wea.Rev.,1988,116(12):2660-2687.
[5]Raymond D J,Jiang H.A theory for long-lived mesoscale convective systems.J.Atmos.Sci.,1990,47(24):3067-3077.
[6]Verlinde J,Cotton W R.A mesoscale vortex couplet observed in the trailing anvil of a multicellular convective complex.Mon.Wea.Rev.,1990,118(5):993-1010.
[7]王金鑫,潘益农,束宇,等.中尺度对流涡旋(MCV)近30 a来的研究进展.气象科学,2014,34(3):343-354.WANG Jinxin,PAN Yinong,SHU Yu,et al.Advance in research on MCV in recent thirty years.Journal of the Meteorological Sciences(in Chinese),2014,34(3):343-354.
[8]王微,潘益农,束宇.中国东部夏季中尺度对流系统以及中尺度对流涡旋的特征.南京大学学报(自然科学),2011,47(6):692-702.WANG Wei,PAN Yinong,SHU Yu.The characteristics of mesoscale convective system and mesoscale convective vortex in summers over eastern China.Journal of Nanjing University(Natural Sciences)(in Chinese),2011,47(6):692-702.
[9]朱爱军,潘益农.中国东部地区一个中尺度对流涡旋的涡度收支分析.南京大学学报(自然科学),2007,43(3):260-269.ZHU Aijun,PAN Yinong.A vorticity budget for a mesoscale convective vortex over East China.Journal of Nanjing University(Natural Sciences)(in Chinese),2007,43(3):260-269.
[10]张元春,孙建华,徐广阔,等.江淮流域两次中尺度对流涡旋的结构特征研究.气候与环境研究,2013,18(3):271-287.ZHANG Yuanchun,SUN Jianhua,XU Guangkuo,et al.Analysis on the structure of two mesoscale convective vortices over YangtzeHuaihe River basin.Climatic and Environmental Research(in Chinese),2013,18(3):271-287.
[11]刘瑞翔,丁治英,王一颉.2007—2013年夏季江淮地区MCS和MCV与暴雨关系的统计特征.气象科学,2016,36(2):236-243.LIU Ruixiang,DING Zhiying,WANG Yijie.Statistical characteristics of relations of rainstorms with MCSs and MCVs in YangtzeHuaihe Basin during summer from 2007 to 2013.Journal of the Meteorological Sciences(in Chinese),2016,36(2):236-243.
[12]王晓芳,汪小康,徐桂荣.2010年长江中游梅雨期β中尺度系统环境特征的分析.高原气象,2013,32(3):750-761.WANG Xiaofang,WANG Xiaokang,XU Guirong.Analysis on environment of meso-β-scale system of continuous heavy rainstorm over the middle reach of Yangtze River during Meiyu period in 2010.Plateau Meteorology(in Chinese),2013,32(3):750-761.
[13]李慧,周顺武,王亚非,等.2010年梅雨期间我国东部地区降水异常的成因.南京信息工程大学学报(自然科学版),2014,6(6):549-557.LI Hui,ZHOU Shunwu,WANG Yafei,et al.Analysis of precipitation anomalies in the middle and lower reaches of the Yangtze River during June-July of 2010.Journal of Nanjing University of Information Science and Technology(Natural Science Edition)(in Chinese),2014,6(6):549-557.
[14]丁治英,高松,常越.MCC转为带状MCSs过程中水平涡度的变化与暴雨的关系.热带气象学报,2013,29(4):540-550.DING Zhiying,GAO Song,CHANG Yue.Relationship between the variation of horizontal vorticity and heavy rain in the process of MCC turning into banded MCSs.Journal of Tropical Meteorology(in Chinese),2013,29(4):540-550.