The development of a vertically aligned vortex is crucial for tropical cyclone(TC)intensification,especially in the presence of environmental vertical wind shear(VWS).In comparison with previous studies,this study pro...The development of a vertically aligned vortex is crucial for tropical cyclone(TC)intensification,especially in the presence of environmental vertical wind shear(VWS).In comparison with previous studies,this study provides more rigorous evidence supporting the role of balanced dynamics in the evolution of vortex tilt by using the potential vorticity(PV)inversion method.Based on two idealized simulations of TCs subjected to nearly constant easterly shear of approximately 6 m s^(–1) and 10 m s^(–1),we demonstrate that the wavenumber-1 circulations directly responsible for vortex tilt evolution are predominantly captured by the balanced component,characterized by vortex Rossby waves.Furthermore,the adiabatic lifting resulting from the balanced response of the shear-tilted vortex contributes to enhanced convection in the TC inner core.As an air parcel undergoes cyclonic rotation,it ascends on the right side of the tilt vector,which increases relative humidity,leads to saturation,and drives the development of convective asymmetries,with maximum upward motion aligned with the tilt direction.This study suggests that the response of TC vortices to the environmental VWS involves complex interactions between vortex tilt,asymmetries in TC structure,and convection,all of which can largely be understood within the framework of balanced dynamics.展开更多
Extreme weather events have been identified as the top global risk for the upcoming decade,according to the Global Risk Report 2025.Between July and September 2024,four tropical cyclones with extreme characteristics m...Extreme weather events have been identified as the top global risk for the upcoming decade,according to the Global Risk Report 2025.Between July and September 2024,four tropical cyclones with extreme characteristics made landfall in China,highlighting the potential impacts of climate change on tropical cyclone activity.Super Typhoon Gaemi made landfall in Taiwan and Fujian provinces,setting record-breaking daily rainfall at 14 meteorological stations in Jiangxi,Hunan,and Liaoning provinces.As the strongest typhoon to make landfall in China during autumn,Yagi maintained super typhoon intensity when making landfall in Hainan,Guangdong provinces in China,and Quang Ninh Province in Vietnam.Typhoon Bebinca and Tropical Storm Pulasan made consecutive landfalls in Shanghai within four days,with Bebinca being the strongest typhoon to strike Shanghai and Jiangsu Province since 1949.The World Weather Attribution report indicates that,due to climate change,rainfall events like those from Super Typhoon Gaemi have become more frequent,now occurring every 20 years in the northern Philippines,every 5 years in Taiwan Province,and every 100 years in Hunan Province.In Taiwan and Hunan provinces,climate change has increased rainfall by 14%and 9%,respectively.It is suggested that exploring how climate change influences the extreme events of landfalling typhoons is an important area for future research.展开更多
Strong vertical motion(>10 m s-1)has profound implications for tropical cyclone(TC)structure changes and intensity.While extreme updrafts in the TC are occasionally observed in real TCs,the associated small-scale f...Strong vertical motion(>10 m s-1)has profound implications for tropical cyclone(TC)structure changes and intensity.While extreme updrafts in the TC are occasionally observed in real TCs,the associated small-scale features remain unclear.Based on an analysis of the extreme eyewall updrafts in two numerical experiments conducted with the Advanced Research version of the Weather Research and Forecasting(WRF)model,in which the large-eddy simulation(LES)technique was used with the finest grid spacings of 37 and 111 m,for the first time this study demonstrates that the simulated extreme updrafts that occur mainly in the enhanced eyewall convection on the down-shear left side are comparable to available observations.The simulated extreme updraft exhibits relatively high frequencies in the lower(750 m),middle(6.5 km)and upper(13 km)troposphere,which are associated with different types of small-scale structures.While the lower-level extreme updraft is mainly related to the tornado-scale vortex,the extreme updraft at upper levels is closely associated with a pair of counter-rotating horizontal rolls oriented generally along the TC tangential flow,which are closely associated with the enhanced eyewall convection.The extreme updraft at middle levels is related to relatively complicated small-scale structures.The study suggests that extreme updrafts can be simulated when the grid spacing is about 100 m or less in the WRF-LES framework,although the simulated small-scale features need further verification in both observation and simulation.展开更多
Previous numerical simulations have focused mainly on the mesoscale structure of the principal rainband in tropical cyclones with a relatively coarse model resolution.In this study,the principal rainband was simulated...Previous numerical simulations have focused mainly on the mesoscale structure of the principal rainband in tropical cyclones with a relatively coarse model resolution.In this study,the principal rainband was simulated in a semi-idealized experiment at a horizontal grid spacing of 1/9 km and its convective-scale structure was examined by comparing the convective elements of the simulated principal rainband with previous observational studies.It is found that the convective scale structure of the simulated principal rainband is well comparable to the observation.The azimuthal variations of the convective scale structure were examined by dividing the simulated principal rainband into the upwind,middle and downwind portions.Some new features are found in the simulated principal rainband.First,the overturning updraft contains small-scale rolls aligned along the inward side of the outward-leaning reflectivity tower in the middle portion.Second,the inner-edge downdraft is combined with a branch of inflow from the upper levels in middle and downwind portions,carrying upper-level dry air to the region between the overturning updrafts and eyewall,and the intrusion of the upper-level dry air further limits the altitude of the overturning updrafts in the middle and downwind portions of the principal rainband.Third,from the middle to downwind portions,the strength of the secondary horizontal wind maximum is gradually replaced by a low-level maximum of the tangential wind collocated with the low-level downdraft.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.42192551,42150710531).
文摘The development of a vertically aligned vortex is crucial for tropical cyclone(TC)intensification,especially in the presence of environmental vertical wind shear(VWS).In comparison with previous studies,this study provides more rigorous evidence supporting the role of balanced dynamics in the evolution of vortex tilt by using the potential vorticity(PV)inversion method.Based on two idealized simulations of TCs subjected to nearly constant easterly shear of approximately 6 m s^(–1) and 10 m s^(–1),we demonstrate that the wavenumber-1 circulations directly responsible for vortex tilt evolution are predominantly captured by the balanced component,characterized by vortex Rossby waves.Furthermore,the adiabatic lifting resulting from the balanced response of the shear-tilted vortex contributes to enhanced convection in the TC inner core.As an air parcel undergoes cyclonic rotation,it ascends on the right side of the tilt vector,which increases relative humidity,leads to saturation,and drives the development of convective asymmetries,with maximum upward motion aligned with the tilt direction.This study suggests that the response of TC vortices to the environmental VWS involves complex interactions between vortex tilt,asymmetries in TC structure,and convection,all of which can largely be understood within the framework of balanced dynamics.
基金supported by the National Natural Science Foundation of China(Grant No.42192551)the National Key Research and Development Program(Grant No.2022YFC3004200)+1 种基金the Innovation and Development Special Program of the China Meteorological Administration(Grant No.CXFZ2024J006)the Special Fund Project of Basic Scientific Research Business Expenses of the Shanghai Typhoon Institute(Grant No.2024JB03).
文摘Extreme weather events have been identified as the top global risk for the upcoming decade,according to the Global Risk Report 2025.Between July and September 2024,four tropical cyclones with extreme characteristics made landfall in China,highlighting the potential impacts of climate change on tropical cyclone activity.Super Typhoon Gaemi made landfall in Taiwan and Fujian provinces,setting record-breaking daily rainfall at 14 meteorological stations in Jiangxi,Hunan,and Liaoning provinces.As the strongest typhoon to make landfall in China during autumn,Yagi maintained super typhoon intensity when making landfall in Hainan,Guangdong provinces in China,and Quang Ninh Province in Vietnam.Typhoon Bebinca and Tropical Storm Pulasan made consecutive landfalls in Shanghai within four days,with Bebinca being the strongest typhoon to strike Shanghai and Jiangsu Province since 1949.The World Weather Attribution report indicates that,due to climate change,rainfall events like those from Super Typhoon Gaemi have become more frequent,now occurring every 20 years in the northern Philippines,every 5 years in Taiwan Province,and every 100 years in Hunan Province.In Taiwan and Hunan provinces,climate change has increased rainfall by 14%and 9%,respectively.It is suggested that exploring how climate change influences the extreme events of landfalling typhoons is an important area for future research.
基金jointly supported by the National Basic Research Program of China(Grant No.2015CB452803)the National Natural Science Foundation of China(Grant Nos.41730961,41675051,41675009,41905001,61827901 and 41675072)the Open Research Program of the State Key Laboratory of Severe Weather(Grant No.2019LASWA02)。
文摘Strong vertical motion(>10 m s-1)has profound implications for tropical cyclone(TC)structure changes and intensity.While extreme updrafts in the TC are occasionally observed in real TCs,the associated small-scale features remain unclear.Based on an analysis of the extreme eyewall updrafts in two numerical experiments conducted with the Advanced Research version of the Weather Research and Forecasting(WRF)model,in which the large-eddy simulation(LES)technique was used with the finest grid spacings of 37 and 111 m,for the first time this study demonstrates that the simulated extreme updrafts that occur mainly in the enhanced eyewall convection on the down-shear left side are comparable to available observations.The simulated extreme updraft exhibits relatively high frequencies in the lower(750 m),middle(6.5 km)and upper(13 km)troposphere,which are associated with different types of small-scale structures.While the lower-level extreme updraft is mainly related to the tornado-scale vortex,the extreme updraft at upper levels is closely associated with a pair of counter-rotating horizontal rolls oriented generally along the TC tangential flow,which are closely associated with the enhanced eyewall convection.The extreme updraft at middle levels is related to relatively complicated small-scale structures.The study suggests that extreme updrafts can be simulated when the grid spacing is about 100 m or less in the WRF-LES framework,although the simulated small-scale features need further verification in both observation and simulation.
基金the National Basic Research Program of China(Grant No.2015CB452803)the National Natural Science Foundation of China(Grant Nos.41730961,41675051,41675009,41675072,41922033 and 41905001)the Open Research Program of the State Key Laboratory of Severe Weather(Grant No.2019LASWA02).
文摘Previous numerical simulations have focused mainly on the mesoscale structure of the principal rainband in tropical cyclones with a relatively coarse model resolution.In this study,the principal rainband was simulated in a semi-idealized experiment at a horizontal grid spacing of 1/9 km and its convective-scale structure was examined by comparing the convective elements of the simulated principal rainband with previous observational studies.It is found that the convective scale structure of the simulated principal rainband is well comparable to the observation.The azimuthal variations of the convective scale structure were examined by dividing the simulated principal rainband into the upwind,middle and downwind portions.Some new features are found in the simulated principal rainband.First,the overturning updraft contains small-scale rolls aligned along the inward side of the outward-leaning reflectivity tower in the middle portion.Second,the inner-edge downdraft is combined with a branch of inflow from the upper levels in middle and downwind portions,carrying upper-level dry air to the region between the overturning updrafts and eyewall,and the intrusion of the upper-level dry air further limits the altitude of the overturning updrafts in the middle and downwind portions of the principal rainband.Third,from the middle to downwind portions,the strength of the secondary horizontal wind maximum is gradually replaced by a low-level maximum of the tangential wind collocated with the low-level downdraft.
