An extreme rainfall event occurred over the middle and lower reaches of the Yangtze Basin(MLY)during the end of June 2016,which was attributable to a Tibetan Plateau(TP)Vortex(TPV)in conjunction with a Southwest China...An extreme rainfall event occurred over the middle and lower reaches of the Yangtze Basin(MLY)during the end of June 2016,which was attributable to a Tibetan Plateau(TP)Vortex(TPV)in conjunction with a Southwest China Vortex(SWCV).The physical mechanism for this event was investigated from Potential Vorticity(PV)and omega perspectives based on MERRA-2 reanalysis data.The cyclogenesis of the TPV over the northwestern TP along with the lower-tropospheric SWCV was found to involve a midtropospheric large-scale flow reconfiguration across western and eastern China with the formation of a high-amplitude Rossby wave.Subsequently,the eastward-moving TPV coalesced vertically with the SWCV over the eastern Sichuan Basin due to the positive vertical gradient of the TPV-related PV advection,leading the lower-tropospheric jet associated with moisture transport to intensify greatly and converge over the downstream MLY.The merged TPV−SWCV specially facilitated the upper-tropospheric isentropic-gliding ascending motion over the MLY.With the TPV-embedded mid-tropospheric trough migrating continuously eastward,the almost stagnant SWCV was re-separated from the overlying TPV,forming a more eastward-tilted high-PV configuration to trigger stronger ascending motion including isentropic-gliding,isentropic-displacement,and diabatic heating-related ascending components over the MLY.This led to more intense rainfall.Quantitative PV diagnoses demonstrate that both the coalescence and subsequent re-separation processes of the TPV with the SWCV were largely dominated by horizontal PV advection and PV generation due to vertically nonuniform diabatic heating,as well as the feedback of condensation latent heating on the isentropic-displacement vertical velocity.展开更多
[Objective] The aim was to study the prediction of summer rainstorm induced by southwest vortex.[Method] Based on 2.5°×2.5° re-analysis data in four time points a day from June to August during 1971-200...[Objective] The aim was to study the prediction of summer rainstorm induced by southwest vortex.[Method] Based on 2.5°×2.5° re-analysis data in four time points a day from June to August during 1971-2008 at 700 hPa in northern hemisphere provided by NECP,rainstorm and southwest vortex from June to August in Guizhou Province were studied systematically,and the forecast data of rainstorm induced by southest vortex was obtained.[Result] Southwest vortex was one of major systems influencing rainstorm in flood season(from June to August),especially in June and July;the occurrence of this kind of rainstorm was closely related to the moving path of southwest vortex,activity of cold air,environmental flow field at 500 hPa,shear line at 850 hPa,southwest jet,position of subtropical high ridge,water vapour conditions,vorticity field,etc.On the basis of factual data,objective forecast system was established and verified by means of similar method and physical diagnosis.The results showed that it was rational to choose upper trough,southwest vortex,conditions of vertical movement,southwest jet,water vapour conditions,etc.as forecast factors;when the center of southwest vortex was located in major key area(100°-105° E,25°-35° N),and secondary key area(105°-108° E,25°-35° N),regional rainstorm occurred most easily,especially in major key area with high frequency of rainstorm.[Conclusion] The study could provide references for the improvement of prediction level of rainstorm induced by southwest vortex,disaster prevention and reduction.展开更多
基于AREM模式对发生在华南地区的3次西南涡暴雨过程进行了数值模拟,并利用模拟结果分析了暴雨过程中西南涡的演变特征,结果表明:高层200 h Pa西风急流入口区、中层500 h Pa西太平洋副热带高压位置、中纬度短波槽、东北亚强冷涡的适当配...基于AREM模式对发生在华南地区的3次西南涡暴雨过程进行了数值模拟,并利用模拟结果分析了暴雨过程中西南涡的演变特征,结果表明:高层200 h Pa西风急流入口区、中层500 h Pa西太平洋副热带高压位置、中纬度短波槽、东北亚强冷涡的适当配置,中低层孟加拉湾和南海暖湿气流的持续输送,是有利于西南涡东移发展,从而造成华南地区持续性强降水的典型环流形势;降水落区与低涡位置密切相关,一般集中在西南涡中心南侧,雨带延伸方向与低涡移动路径一致;而其强度则与低涡中心区域位势高度等值线梯度及低层大气风场强度息息相关。西南涡中心低层为东风和弱北风,中层以南风为主,高层为强西风和弱北风,低层辐合、高层辐散及正涡度结构特征显著。涡度平流项和辐合辐散项的作用集中体现在中低层大气,涡度对流项、扭转项的作用则在中高层更为明显,而涡度辐合辐散项对西南涡的发展加强起最主要的作用。展开更多
基金This research was jointly supported by the National Natural Science Foundation of China(Grant Nos.41730963 and 41876020)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB40000000).
文摘An extreme rainfall event occurred over the middle and lower reaches of the Yangtze Basin(MLY)during the end of June 2016,which was attributable to a Tibetan Plateau(TP)Vortex(TPV)in conjunction with a Southwest China Vortex(SWCV).The physical mechanism for this event was investigated from Potential Vorticity(PV)and omega perspectives based on MERRA-2 reanalysis data.The cyclogenesis of the TPV over the northwestern TP along with the lower-tropospheric SWCV was found to involve a midtropospheric large-scale flow reconfiguration across western and eastern China with the formation of a high-amplitude Rossby wave.Subsequently,the eastward-moving TPV coalesced vertically with the SWCV over the eastern Sichuan Basin due to the positive vertical gradient of the TPV-related PV advection,leading the lower-tropospheric jet associated with moisture transport to intensify greatly and converge over the downstream MLY.The merged TPV−SWCV specially facilitated the upper-tropospheric isentropic-gliding ascending motion over the MLY.With the TPV-embedded mid-tropospheric trough migrating continuously eastward,the almost stagnant SWCV was re-separated from the overlying TPV,forming a more eastward-tilted high-PV configuration to trigger stronger ascending motion including isentropic-gliding,isentropic-displacement,and diabatic heating-related ascending components over the MLY.This led to more intense rainfall.Quantitative PV diagnoses demonstrate that both the coalescence and subsequent re-separation processes of the TPV with the SWCV were largely dominated by horizontal PV advection and PV generation due to vertically nonuniform diabatic heating,as well as the feedback of condensation latent heating on the isentropic-displacement vertical velocity.
文摘[Objective] The aim was to study the prediction of summer rainstorm induced by southwest vortex.[Method] Based on 2.5°×2.5° re-analysis data in four time points a day from June to August during 1971-2008 at 700 hPa in northern hemisphere provided by NECP,rainstorm and southwest vortex from June to August in Guizhou Province were studied systematically,and the forecast data of rainstorm induced by southest vortex was obtained.[Result] Southwest vortex was one of major systems influencing rainstorm in flood season(from June to August),especially in June and July;the occurrence of this kind of rainstorm was closely related to the moving path of southwest vortex,activity of cold air,environmental flow field at 500 hPa,shear line at 850 hPa,southwest jet,position of subtropical high ridge,water vapour conditions,vorticity field,etc.On the basis of factual data,objective forecast system was established and verified by means of similar method and physical diagnosis.The results showed that it was rational to choose upper trough,southwest vortex,conditions of vertical movement,southwest jet,water vapour conditions,etc.as forecast factors;when the center of southwest vortex was located in major key area(100°-105° E,25°-35° N),and secondary key area(105°-108° E,25°-35° N),regional rainstorm occurred most easily,especially in major key area with high frequency of rainstorm.[Conclusion] The study could provide references for the improvement of prediction level of rainstorm induced by southwest vortex,disaster prevention and reduction.
文摘基于AREM模式对发生在华南地区的3次西南涡暴雨过程进行了数值模拟,并利用模拟结果分析了暴雨过程中西南涡的演变特征,结果表明:高层200 h Pa西风急流入口区、中层500 h Pa西太平洋副热带高压位置、中纬度短波槽、东北亚强冷涡的适当配置,中低层孟加拉湾和南海暖湿气流的持续输送,是有利于西南涡东移发展,从而造成华南地区持续性强降水的典型环流形势;降水落区与低涡位置密切相关,一般集中在西南涡中心南侧,雨带延伸方向与低涡移动路径一致;而其强度则与低涡中心区域位势高度等值线梯度及低层大气风场强度息息相关。西南涡中心低层为东风和弱北风,中层以南风为主,高层为强西风和弱北风,低层辐合、高层辐散及正涡度结构特征显著。涡度平流项和辐合辐散项的作用集中体现在中低层大气,涡度对流项、扭转项的作用则在中高层更为明显,而涡度辐合辐散项对西南涡的发展加强起最主要的作用。
