The Pearl River Delta(PRD),a tornado hotspot,forms a distinct trumpet-shaped coastline that concaves toward the South China Sea.During the summer monsoon season,low-level southwesterlies over the PRD’s sea surface te...The Pearl River Delta(PRD),a tornado hotspot,forms a distinct trumpet-shaped coastline that concaves toward the South China Sea.During the summer monsoon season,low-level southwesterlies over the PRD’s sea surface tend to be turned toward the west coast,constituting a convergent wind field along with the landward-side southwesterlies,which influences regional convective weather.This two-part study explores the roles of this unique land–sea contrast of the trumpet-shaped coastline in the formation of a tornadic mesovortex within monsoonal flows in this region.Part I primarily presents observational analyses of pre-storm environments and storm evolutions.The rotating storm developed in a lowshear environment(not ideal for a supercell)under the interactions of three air masses under the influence of the land–sea contrast,monsoon,and storm cold outflows.This intersection zone(or“triple point”)is typically characterized by local enhancements of ambient vertical vorticity and convergence.Based on a rapid-scan X-band phased-array radar,finger-like echoes were recognized shortly after the gust front intruded on the triple point.Developed over the triple point,they rapidly wrapped up with a well-defined low-level mesovortex.It is thus presumed that the triple point may have played roles in the mesovortex genesis,which will be demonstrated in Part II with multiple sensitivity numerical simulations.The findings also suggest that when storms pass over the boundary intersection zone in the PRD,the expected possibility of a rotating storm occurring is relatively high,even in a low-shear environment.Improved knowledge of such environments provides additional guidance to assess the regional tornado risk.展开更多
Supercells are the most severe and long-lasting type of highly organized convective storms,with the greatest potential for producing extreme weather events and causing significant disasters.This article provides a com...Supercells are the most severe and long-lasting type of highly organized convective storms,with the greatest potential for producing extreme weather events and causing significant disasters.This article provides a comprehensive overview and recent highlights of supercell research,including the unique structure,environmental characteristics,and the formation and maintenance mechanisms of the mesocyclone.Buoyancy instability is a necessary ingredient in the supercell’s environment,whereas dynamic factors such as vertical wind shear and low-level storm relative helicity are more sensitive parameters for distinguishing supercells from non-supercells.The near-storm environmental parameters derived from multi-sensor observations are expected to enhance high-resolution nowcasting of supercell storms.Different types of supercells,including those producing distinct hazardous weather,exhibit unique reflectivity morphology and dynamical/microphysical structures,e.g.,tornadic supercells have a strong low-level mesocyclone while severe hail supercells feature a strong and deep mesocyclone.Mesocyclones associated with damaging winds are accompanied by significant mid-level radial convergence,while those responsible for heavy precipitation are typically located at low levels.The vertical vorticity of the mesocyclone is generated through the tilting of environmental horizontal vorticity by storm-related intense updrafts.The horizontal vorticity that tilts into the mid-level mesocyclone originates from the environmental vertical wind shear,which produces the horizontal vorticity along the inflow to the storms.In contrast,the horizontal vorticity contributing to the low-level mesocyclone derives from two distinct mechanisms,i.e.,environmental vertical shear in the boundary layer and gust front-induced baroclinicity.It remains unclear which mechanism is more dominant.Moreover,the maintenance and enhancement mechanisms of mesocyclones are complex and vary across different scenarios,particularly when embedded within heavy precipitation,during storm mergers,or in proximity to surface mesoscale boundaries(e.g.,fronts,drylines,gust fronts,and their associated convergence lines).In recent years,based on super high-resolution numerical experiment results,the physical conceptual models of the supercell tornadogenesis have been updated.The newly revealed microphysical and dynamic characteristics from polarimetric Doppler radar observations enable more accurate hail size detection.However,the refined physical conceptual model of severe hail growth still requires improvement,and our understanding of the formation mechanisms behind extreme wind gusts and flash floods associated with supercells remains limited.展开更多
This article reviews the advances in severe convection research and operation in China during the past several decades.The favorable synoptic situations for severe convective weather(SCW),the major organization modes ...This article reviews the advances in severe convection research and operation in China during the past several decades.The favorable synoptic situations for severe convective weather(SCW),the major organization modes of severe convective storms(SCSs),the favorable environmental conditions and characteristics of weather radar echoes and satellite images of SCW and SCSs,and the forecasting and nowcasting techniques of SCW,are emphasized.As a whole,Chinese scientists have achieved a profound understanding of the synoptic patterns,organization,and evolution characteristics of SCW from radar and satellite observations,and the mechanisms of different types of convective weather in China.Specifically,in-depth understanding of the multiple types of convection triggers,along with the environmental conditions,structures and organization modes,and maintenance mechanisms of supercell storms and squall lines,has been obtained.The organization modes and climatological distributions of mesoscale convective systems and different types of SCW,and the multiscale characteristics and formation mechanisms of large hail,tornadoes,downbursts,and damaging convective wind gusts based on radar,satellite,and lightning observations,as well as the related features from damage surveys,are elucidated.In terms of operational applications,different types of identification and mesoanalysis techniques,and various forecasting and nowcasting techniques using methods such as the"ingredients-based"and deep learning algorithms,have been developed.As a result,the performance of operational SCW forecasts in China has been significantly improved.展开更多
In this paper,synoptic-scale analyses of frontogenesis,moisture budget,and tropospheric diabatic heating are performed to reveal the development and maintenance mechanisms for the extreme heavy rainfall in Henan Provi...In this paper,synoptic-scale analyses of frontogenesis,moisture budget,and tropospheric diabatic heating are performed to reveal the development and maintenance mechanisms for the extreme heavy rainfall in Henan Province of central China from 19 to 21 July 2021,based on station observations and the ECMWF Reanalysis version 5(ERA5)data.The results demonstrate that owing to the blocking effect of local topography,low-level wind convergence in Henan appeared underneath high-level divergence,conducive to development and maintenance of a midtropospheric low-pressure system saddled by the Asian continental high and the western Pacific subtropical high(WPSH),during the extreme heavy rainfall.In the lower troposphere,frontogenesis occurred in the θ_(se) intensive region,as a result of the divergence and horizontal deformation(which play equally important roles),generating frontal secondary circulation with strong vertical motion favorable to heavy rainfall.Moisture budget analysis reveals that 1)with the continuous strengthening of the easterly wind from the north side of Typhoon In-Fa(2106),strong wind shear and orographic uplift led to abnormally strong convergence of water vapor flux in the boundary layer in Henan;2)there occurred extremely strong net inflow of moisture in the boundary layer from the east.Horizontally,both the apparent heat source and the moisture sink coincided with the area of heavy rainfall;vertically,however,Q_(1)exhibited a single peak with the heating center in the middle and upper troposphere,while large Q_(2)values evenly resided over 850–400 hPa;and Q_(1)(Q_(2))was dominated by vertical(horizontal)transport of potential temperature(moisture).These indicate that the latent heat release from condensation of initial heavy rainfall provided a positive feedback,leading to increasingly heavy precipitation.All these synoptic settings sustained the extreme rainfall process.展开更多
基金supported by the Guangdong Major Project of Basic and Applied Basic Research(Grant No.2020B0301030004)the National Natural Science Foundation of China(Grant Nos.42275006 and 42030604)+1 种基金the Guangdong Basic and Applied Basic Research Foundation(Grant No.2023A1515011705)the Science and Technology Research Project for Society of Foshan(Grant No.2120001008761).
文摘The Pearl River Delta(PRD),a tornado hotspot,forms a distinct trumpet-shaped coastline that concaves toward the South China Sea.During the summer monsoon season,low-level southwesterlies over the PRD’s sea surface tend to be turned toward the west coast,constituting a convergent wind field along with the landward-side southwesterlies,which influences regional convective weather.This two-part study explores the roles of this unique land–sea contrast of the trumpet-shaped coastline in the formation of a tornadic mesovortex within monsoonal flows in this region.Part I primarily presents observational analyses of pre-storm environments and storm evolutions.The rotating storm developed in a lowshear environment(not ideal for a supercell)under the interactions of three air masses under the influence of the land–sea contrast,monsoon,and storm cold outflows.This intersection zone(or“triple point”)is typically characterized by local enhancements of ambient vertical vorticity and convergence.Based on a rapid-scan X-band phased-array radar,finger-like echoes were recognized shortly after the gust front intruded on the triple point.Developed over the triple point,they rapidly wrapped up with a well-defined low-level mesovortex.It is thus presumed that the triple point may have played roles in the mesovortex genesis,which will be demonstrated in Part II with multiple sensitivity numerical simulations.The findings also suggest that when storms pass over the boundary intersection zone in the PRD,the expected possibility of a rotating storm occurring is relatively high,even in a low-shear environment.Improved knowledge of such environments provides additional guidance to assess the regional tornado risk.
基金Supported by the National Natural Science Foundation of China(42375018 and U2142203)Key Innovation Team of China Meteorological Administration(CMA2022ZD07)Youth Research Project of China Meteorological Administration Training Centre(2023CMATCQN03)。
文摘Supercells are the most severe and long-lasting type of highly organized convective storms,with the greatest potential for producing extreme weather events and causing significant disasters.This article provides a comprehensive overview and recent highlights of supercell research,including the unique structure,environmental characteristics,and the formation and maintenance mechanisms of the mesocyclone.Buoyancy instability is a necessary ingredient in the supercell’s environment,whereas dynamic factors such as vertical wind shear and low-level storm relative helicity are more sensitive parameters for distinguishing supercells from non-supercells.The near-storm environmental parameters derived from multi-sensor observations are expected to enhance high-resolution nowcasting of supercell storms.Different types of supercells,including those producing distinct hazardous weather,exhibit unique reflectivity morphology and dynamical/microphysical structures,e.g.,tornadic supercells have a strong low-level mesocyclone while severe hail supercells feature a strong and deep mesocyclone.Mesocyclones associated with damaging winds are accompanied by significant mid-level radial convergence,while those responsible for heavy precipitation are typically located at low levels.The vertical vorticity of the mesocyclone is generated through the tilting of environmental horizontal vorticity by storm-related intense updrafts.The horizontal vorticity that tilts into the mid-level mesocyclone originates from the environmental vertical wind shear,which produces the horizontal vorticity along the inflow to the storms.In contrast,the horizontal vorticity contributing to the low-level mesocyclone derives from two distinct mechanisms,i.e.,environmental vertical shear in the boundary layer and gust front-induced baroclinicity.It remains unclear which mechanism is more dominant.Moreover,the maintenance and enhancement mechanisms of mesocyclones are complex and vary across different scenarios,particularly when embedded within heavy precipitation,during storm mergers,or in proximity to surface mesoscale boundaries(e.g.,fronts,drylines,gust fronts,and their associated convergence lines).In recent years,based on super high-resolution numerical experiment results,the physical conceptual models of the supercell tornadogenesis have been updated.The newly revealed microphysical and dynamic characteristics from polarimetric Doppler radar observations enable more accurate hail size detection.However,the refined physical conceptual model of severe hail growth still requires improvement,and our understanding of the formation mechanisms behind extreme wind gusts and flash floods associated with supercells remains limited.
基金Supported by the National Key Research and Development Program of China(2018YFC1507504 and 2017YFC1502000)National Natural Science Foundation of China(41775044 and 41375051)Strategic Research Projects on Medium-and Long-term Development of Chinese Engineering Science and Technology(2019-ZCQ-06)。
文摘This article reviews the advances in severe convection research and operation in China during the past several decades.The favorable synoptic situations for severe convective weather(SCW),the major organization modes of severe convective storms(SCSs),the favorable environmental conditions and characteristics of weather radar echoes and satellite images of SCW and SCSs,and the forecasting and nowcasting techniques of SCW,are emphasized.As a whole,Chinese scientists have achieved a profound understanding of the synoptic patterns,organization,and evolution characteristics of SCW from radar and satellite observations,and the mechanisms of different types of convective weather in China.Specifically,in-depth understanding of the multiple types of convection triggers,along with the environmental conditions,structures and organization modes,and maintenance mechanisms of supercell storms and squall lines,has been obtained.The organization modes and climatological distributions of mesoscale convective systems and different types of SCW,and the multiscale characteristics and formation mechanisms of large hail,tornadoes,downbursts,and damaging convective wind gusts based on radar,satellite,and lightning observations,as well as the related features from damage surveys,are elucidated.In terms of operational applications,different types of identification and mesoanalysis techniques,and various forecasting and nowcasting techniques using methods such as the"ingredients-based"and deep learning algorithms,have been developed.As a result,the performance of operational SCW forecasts in China has been significantly improved.
基金Supported by the National Natural Science Foundation of China(41875058 and 42275013)Weather Nowcasting Project for Teaching and Research Teams of China Meteorological Administration+1 种基金Research Project for Young Talents of China Meteorological Administration Training Centre(2022CMATCQN03)Innovation and Development Program of China Meteorological Administration。
文摘In this paper,synoptic-scale analyses of frontogenesis,moisture budget,and tropospheric diabatic heating are performed to reveal the development and maintenance mechanisms for the extreme heavy rainfall in Henan Province of central China from 19 to 21 July 2021,based on station observations and the ECMWF Reanalysis version 5(ERA5)data.The results demonstrate that owing to the blocking effect of local topography,low-level wind convergence in Henan appeared underneath high-level divergence,conducive to development and maintenance of a midtropospheric low-pressure system saddled by the Asian continental high and the western Pacific subtropical high(WPSH),during the extreme heavy rainfall.In the lower troposphere,frontogenesis occurred in the θ_(se) intensive region,as a result of the divergence and horizontal deformation(which play equally important roles),generating frontal secondary circulation with strong vertical motion favorable to heavy rainfall.Moisture budget analysis reveals that 1)with the continuous strengthening of the easterly wind from the north side of Typhoon In-Fa(2106),strong wind shear and orographic uplift led to abnormally strong convergence of water vapor flux in the boundary layer in Henan;2)there occurred extremely strong net inflow of moisture in the boundary layer from the east.Horizontally,both the apparent heat source and the moisture sink coincided with the area of heavy rainfall;vertically,however,Q_(1)exhibited a single peak with the heating center in the middle and upper troposphere,while large Q_(2)values evenly resided over 850–400 hPa;and Q_(1)(Q_(2))was dominated by vertical(horizontal)transport of potential temperature(moisture).These indicate that the latent heat release from condensation of initial heavy rainfall provided a positive feedback,leading to increasingly heavy precipitation.All these synoptic settings sustained the extreme rainfall process.
