By using the high spatial and temporal resolution Jinan Doppler Weather Radar data and Jinan,Xingtai sounding data,the radar signature and mesocyclone parameters of 54 supercells during 2003-2008 were analyzed.The res...By using the high spatial and temporal resolution Jinan Doppler Weather Radar data and Jinan,Xingtai sounding data,the radar signature and mesocyclone parameters of 54 supercells during 2003-2008 were analyzed.The results showed that the probability of a supercell forming would be higher when SI (showalter index) ≤ -2℃,K (K index) ≥ 30℃ and 0-6 km wind shear>15 m/s.The supercell storms can generally be divided into two categories,namely,type of isolation and mosaic type.To the type of isolation,the max reflectivity,cell-based VIL,max reflectivity height,cell top,mesocyclone base and top were significantly higher than the mosaic type.Isolation-type supercells had significantly higher probability of hail,lower probability of gale than the mosaic category.The mesocyclone attribute differences between isolation-type and mosaic type supercells determined the differences of storm structures and severe weather phenomenon.展开更多
This study investigates the characteristics of a heavy snowfall event over the southwestern part of the Korean Peninsula on 4 December 2005. The snowstorm was a type of mesoscale maritime cyclone which resulted from b...This study investigates the characteristics of a heavy snowfall event over the southwestern part of the Korean Peninsula on 4 December 2005. The snowstorm was a type of mesoscale maritime cyclone which resulted from barotropic instability, and diabatic heating from the warm ocean in continental polar air masses. Based on surface observations, radiosonde soundings, MTSAT-1R satellite data and the 10-km grid RDAPS （Regional Assimilation and Prediction System based on the PSU/NCAR MM5） data, the evolution of the mesocyclone is explained by the following dynamics; （1） In the initial stage, the primary role in the cyclogenesis process of the mesocyclone is a barotropic instability in the horizontal shear zone. （2） In the developing stage, the mesocyclone moves and deepens into a baroclinic zone corresponding to the surface heating and moistening. （3） In the mature stage, it is found that the mesocyclone is intensified by the destabilization caused by enhanced low-level heating and condensation, the moisture flux convergence, and the interaction between upper and lower-level potential vorticity anomalies. We suggest that a checklist with stepwise indicators responsible for development be prepared for the forecasting of heavy snowfall over the southwestern part of the Korean Peninsula.展开更多
A total of 61 supercells with mesocyclones lasting for at least 6 volume scans were investigated. These storm parameters and mesocyclone parameters were counted and compared to determine the salient differences betwee...A total of 61 supercells with mesocyclones lasting for at least 6 volume scans were investigated. These storm parameters and mesocyclone parameters were counted and compared to determine the salient differences between isolated supercells and embedded supercells in different regions. The results showed that the mesocyclone parameters had different evolution characteristics in three stages of mesocyclone. The storm parameters, mesocyclone parameters and severe weather phenomenon had significantly differences between isolated supercells and embedded supercells. The mesocyclone parameter differences determined the differences in the reflectivity structure and weather phenomenon. The higher base and top of mesocyclone for isolated supercells indicated that the isolated supercells had higher maximum reflectivity, maximum reflectivity height, cell-based vertically integrated liquid and top of storm cell, and significantly higher probability of hail or large hail than the embedded supercells. The descending lower base of mesocyclone at its mature stage in the region of Jianghuai Plain indicated that the supercells in this region had a higher probability of mesocyclone-induced tornado.展开更多
This study presents finely resolved radar signatures of multiple cyclonic vortices associated with an EF2 tornadic supercell that occurred in Guangzhou on 16 June 2022 and discusses how the mesocyclone formed on the l...This study presents finely resolved radar signatures of multiple cyclonic vortices associated with an EF2 tornadic supercell that occurred in Guangzhou on 16 June 2022 and discusses how the mesocyclone formed on the lee side of mountain.A nearby X-band phased-array radar provides evidence that the mesocyclone was shallow,with a depth generally confined to less than 3 km.The mesocyclonic feature was observed to initiate from near-ground level,driven by the interaction between intensifying cold pool surges and shallow lee-side ambient flows.It was first recognized shortly after the presence of near-ground cyclonic convergence signatures over the leading edges of cold pool outflows.Over the subsequent 17 min,the mesocyclone developed upward,reaching a maximum height of 3 km,and produced a tornado 8min later.Nearly coinciding with the time of tornadogenesis,a noticeable separation of the low-level tornado cyclone from the midlevel mesocyclone was observed.This shift in the vertically oriented vortex tube was likely caused by modifications to the low-level flow due to the complex hilly terrain or by occlusions associated with rear-flank downdrafts.After tornadogenesis,high-resolution X-PAR observations revealed that the lowest-level mesocyclonic signature contracted into a gate-to-gate tornadic vortex signature(TVS)at the tip of hook echoes.Compared to conventional S-band operational weather radars,rapid-scan X-PAR observations indicate that a core diameter threshold of 1.5–2 km could be employed to identify a cyclonically sheared radial velocity couplet as a TVS,potentially extending the lead time for Doppler-based tornado warnings.展开更多
In this study, the kinematic and precipitation structures of a mesocyclone associated with a hook echo were analyzed using single Doppler radar data. The mesocyclone was embedded in a mesoscale convective rainband nea...In this study, the kinematic and precipitation structures of a mesocyclone associated with a hook echo were analyzed using single Doppler radar data. The mesocyclone was embedded in a mesoscale convective rainband near northern Taiwan coastline on 10 September 2004. The synoptic environment was characterized by a moderate convective available potential energy （CAPE） and a moderate ambient vertical shear from surface to 5 km. In addition, a pronounced low-level mesoscale shear/convergence zone, which resulted from the interaction of two tropical depressions, was also identified in the northwest coast of Taiwan, providing a favorable dynamic condition for the development of the mesocyclone. Analyzing single Doppler dipole signature shows that this mesocyclone formed initially at low levels, then deepened and strengthened rapidly into mature stage with the vertical depth exceeding 8 km. The diameter of the mesocyclone decreased with the height at the time of vortexgenesis, and then evolved into columnar structure accompanied with the broader diameter in middle layer. The mesocyclone lasted for about 2 h. The Ground-Based Velocity Track Display （GBVTD） method was applied to retrieve the ax- isymmetric circulation of the mesocyclone. The GBVTD-derived primary circulation showed the radius of maximum wind （RMW） of the mesocyclone was about 5-6 km and varied from inward tilting to outward tilting with time. The axisymmetric radial wind field was initially characterized by a low-level inflow inside the RMW and outflow outside the RMW, respectively. The strongest reflectivity was associated with a stronger updraft near the RMW, and a weak downdraft was located at the center of the mesocyclone. Subsequently the downdraft and reflectivity near the mesocyclone center strengthened obviously, accompanied with the low-level outflow, strong updraft as well as high reflectivity extending outside the RMW. The relative tangential wind initially exhibited a wavenumber 1 asymmetric structure with the maximum wind region at the left portion of the meso cyclone and shifted counterclockwise with height. The axisymmetric tangential wind strengthened and reached its maximum intensity with a value about 20 m s^-1 at z=1 km. After that the axisymmetric tangential wind decreased rapidly, meanwhile the wave-1 asymmetric structure redeveloped with the maximum wind at the left-front of motion. In summary, the evolution and structure of the mesocyclone is similar to that observed within a non-supercell mesocyclone. It is worth to mention that the axisymmetric circulation characteristics of the mesocyclone at its mature stage are very similar to those observed in a mature typhoon. However, there are significant differences, i.e., the size is much smaller, the lifetime is much shorter, and the downdraft in the center is produced by precipitation instead of compensating subsidence.展开更多
The X-band phased array radar offers faster scanning speed and higher spatial resolution compared to the S-band radar,making it capable of enhancing tornado monitoring and early warning capabilities.This study analyze...The X-band phased array radar offers faster scanning speed and higher spatial resolution compared to the S-band radar,making it capable of enhancing tornado monitoring and early warning capabilities.This study analyzed the characteristics and nowcasting signals of a tornado case that occurred on June 16,2022 in the Guangzhou region.Our findings indicate that the violent contraction of rotation radius and the dramatic increase in rotation speed were important signal characteristics associated with tornado formation.The X-band phased array radar,with its high temporal and spatial resolution,provided an opportunity to capture early warning signals from polarimetric characteristics.The X-band phased array radar demonstrated noteworthy ability to identify apparent tornado vortex signature(TVS)features in a 10-minute lead time,surpassing the capabilities of the CINRAD/SA radar.Additionally,due to its higher scanning frequency,the Xband phased-array radar was capable of consistently identifying TVS with shorter intervals,enabling a more precise tracking of the tornado's path.The application of professional radars,in this case,provides valuable insights for the monitoring of evolutions of severe local storms and even tornadoes and the issuance of early warning signals.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
Hurricane Ida ferociously affected many south-eastern and eastern parts of the United States,making it one of the strongest hurricanes in recent years.Advanced forecast and warning tool has been used to track the path...Hurricane Ida ferociously affected many south-eastern and eastern parts of the United States,making it one of the strongest hurricanes in recent years.Advanced forecast and warning tool has been used to track the path of the ex-Hurricane,Ida,as it left New Orleans on its way towards the northeast,accurately predicting significant supercell development above New York City on September 01,2021.This advanced method accurately detected the area with the highest possible level of convective instability with 24-h lead time and even Level 5,devised in the categorical outlooks legend of the system.Therefore,an extreme level implied a very high probability of the local-scale hazard occurring above the NYC.Cloud model output fields(updrafts and downdrafts,wind shear,near-surface convergence,the vertical component of relative vorticity)show the rapid development of a strong supercell storm with rotating updrafts and a mesocyclone.The characteristic hook-shaped echo signature visible in the reflectivity patterns indicates a signal for a highly precipitable(HP)supercell with the possibility of tornado initiation.Open boundary conditions represent a good basis for simulating a tornado that evolved from a supercell storm,initialized with initial data obtained from a real-time simulation in the period when the bow echo and tornado-like signature occurred.Тhe modeled results agree well with the observations.展开更多
In this study,single Doppler radar data were used to examine the structure and evolution of a high precipitation（HP） supercell embedded in a cold front near Jianyang,Fujian Province on 12 April 2003.The synoptic env...In this study,single Doppler radar data were used to examine the structure and evolution of a high precipitation（HP） supercell embedded in a cold front near Jianyang,Fujian Province on 12 April 2003.The synoptic environment was characterized by high humidity at low levels,moderate CAPE（convective available potential energy;1601 J kg^（-1））,moderate wind shear（22 m s^（-1） in 0-5 km）,and veering of the horizontal winds with height,similar to those HP supercells previously observed in midlatitudes.In addition,the calculated bulk Richardson number was only 16,suggesting favorable environmental conditions for supercell development. The documented storm was located at the leading edge of a squall line.It was initiated from a single cell at 0732 UTC.It evolved into a bow shape gradually,and then split into two separate storms along the storm motion direction through the apex of the bow echo.The left-moving storm dissipated rapidly, but the right-moving storm strengthened and evolved into an HP supercell,lasting for more than 1 h.The radar reflectivity of the HP supercell during its mature stage showed a typical low-level hook echo at the front flank of the storm with its maximum reflectivity beyond 70 dBZ.Above the hook echo,an elevated maximum reflectivity core accompanied by a bounded weak-echo region（BWER） and a down-shear echo overhanging aloft were clearly identified.The elevated BWER,marked by 40-50-dBZ reflectivity values,was surrounded by values of 60-70 dBZ.A well-defined mesocyclone lasted about 1 h and was collocated with the low-level WER and middle-level BWER.The radar-estimated time-height profiles of mesocyclone rotational velocity and diameter indicated that this mesocyclone formed initially at middle level,then deepened and strengthened rapidly with the vertical depth deeper than 8 km and rotational velocity stronger than 24 m s^（-1） at the mature stage,and later decayed rapidly.The GBVTD（ground-based velocity track display）-derived primary circulation showed that the maximum tangential wind of the mesocyclone appeared at middle level （3-5 km） with a value of about 20 m s^（-1）.The mean radial wind field was characterized with a low-level inflow below 4 km,and accompanied by stronger updraft near the mesocyclone center.Between 4 and 7 km.the tangential wind profile resembled a Rankine combined vortex with the radius of maximum wind （RMW） at 3 km.and there was outflow/inflow inside/outside of the RMW.Correspondingly,the vertical velocity indicated a stronger updraft at the RMW and a weak downdraft inside the RMW.Above 7 km,the outflow strengthened and extended outside the RMW. In summary,the reflectivity structures of the storm and the accompanying mesocyclone were similar to those midlatitude HP supercells proposed in Miller＇s paper in 1994.However,the evolution of the HP supercell,including its three stages：ordinary storm,bow echo,and storm splitting,was quite different from those documented before.展开更多
Three supercell storms on 24 June 2004（0624）,28 June 2003（0628）,and 27 September 2002（0927） induced different damages in Shandong Province.Storm 0927 was inferior in size and intensity to storms 0628 and 0624.Th...Three supercell storms on 24 June 2004（0624）,28 June 2003（0628）,and 27 September 2002（0927） induced different damages in Shandong Province.Storm 0927 was inferior in size and intensity to storms 0628 and 0624.The structure and evolvement of the three storms were analyzed in detail based on the WSR98D radar data in combination with weather charts.The results show that mesoscale surface convergence triggered release of instable energy,which resulted in severe convection.During the development stage,storms 0927,0628,and 0624 displayed multi-cell propagation,single-cell evolution,and multi-cell mergence,respectively.The storm tracks were similar：they were all right-moving supercell storms,i.e.,moving at an angle of 30°-70° to the right of the mean wind and at a speed of about 45%-70% of the mean wind speed.In the mature stage,the maximum reflectivity appeared at the low level in storm 0927,mid level in storm 0628,and mid-upper level in storm 0624.These storms possessed almost all typical features of supercell storms：weak echo region（WER）,bounded weak echo region（BWER）,and mesocyclone.An organized mesocyclone formed at the middle height of an updraft,deepened gradually downward and upward,and became a typical mid-level mesocyclone with strong updrafts.The vertical structures of airflows in the three storms were similar,i.e.,significant convergence at low level,nearly pure rotation at mid level,and divergent rotation at upper level.However,signatures of mid-level horizontal airflows in the three storms were different：at mid level,there was a single vortex in storm 0628,but a double-vortex flow pattern was seen in storms 0927 and 0624.The horizontal structure of the double-vortex flow was hard to be blown away by the environmental airflow,and thus the storms could persist for a longer period of time than the single vortex storm.展开更多
The understanding of unusual supercell outbreaks remains limited.This study examines the development and environmental conditions of a supercell outbreak event that occurred on 26 March 2022,when 19 supercells formed ...The understanding of unusual supercell outbreaks remains limited.This study examines the development and environmental conditions of a supercell outbreak event that occurred on 26 March 2022,when 19 supercells formed within just 6 h in the coastal region of southern China.The focus is on analyzing radar characteristics and highlighting the role of a surface cold front in driving the development of rotating storms.The cold front created significant variations in low-level vertical wind shear and conditional instability on its warm and cool sides.Most of the 19 supercells formed along the front or on its adjacent cool side.Both observations and simulations reveal that favorable dynamic conditions for supercell development appeared and concentrated in a relatively narrow area on the cool side of the front,influenced by directional wind shear near the surface,which drove the formation and positioning of supercells.Numerical simulations demonstrate that the supercells developed their rotating updrafts upon encountering the 2-4-km scale misocyclones located at the convergent boundary of the cold front.The rotating storms were enhanced when they traversed the intersection zone created by the cold front and convergent boundaries under the influence of the unique land-sea contrast of the Pearl River Delta.In sum,appropriate dynamic allocation of wind shear,cold front,and landform has facilitated development of the clustered supercell outbreak.These findings may offer valuable insights on improving severe weather forecasts in this tornado-prone area.展开更多
基金Supported by The Project from Department of Science and Technology of Shandong Province Under Grant No. 2007GG20008001 and 2010GSF10805
文摘By using the high spatial and temporal resolution Jinan Doppler Weather Radar data and Jinan,Xingtai sounding data,the radar signature and mesocyclone parameters of 54 supercells during 2003-2008 were analyzed.The results showed that the probability of a supercell forming would be higher when SI (showalter index) ≤ -2℃,K (K index) ≥ 30℃ and 0-6 km wind shear>15 m/s.The supercell storms can generally be divided into two categories,namely,type of isolation and mosaic type.To the type of isolation,the max reflectivity,cell-based VIL,max reflectivity height,cell top,mesocyclone base and top were significantly higher than the mosaic type.Isolation-type supercells had significantly higher probability of hail,lower probability of gale than the mosaic category.The mesocyclone attribute differences between isolation-type and mosaic type supercells determined the differences of storm structures and severe weather phenomenon.
基金Acknowledgements. This work was supported by a grant of ＂Eco-Technopia 21 Project＂ by Korean Ministry of Environment. This work was also supported by the Brain Korea 21 Project in 2006/7. Reviewer Prof. Gang Fu＇s constructive comments and suggestions are greatly appreciated. Also, we thank the Information Management Division of Korean Meteorological Administration for providing us with the Forecaster＇s Analysis System.
文摘This study investigates the characteristics of a heavy snowfall event over the southwestern part of the Korean Peninsula on 4 December 2005. The snowstorm was a type of mesoscale maritime cyclone which resulted from barotropic instability, and diabatic heating from the warm ocean in continental polar air masses. Based on surface observations, radiosonde soundings, MTSAT-1R satellite data and the 10-km grid RDAPS （Regional Assimilation and Prediction System based on the PSU/NCAR MM5） data, the evolution of the mesocyclone is explained by the following dynamics; （1） In the initial stage, the primary role in the cyclogenesis process of the mesocyclone is a barotropic instability in the horizontal shear zone. （2） In the developing stage, the mesocyclone moves and deepens into a baroclinic zone corresponding to the surface heating and moistening. （3） In the mature stage, it is found that the mesocyclone is intensified by the destabilization caused by enhanced low-level heating and condensation, the moisture flux convergence, and the interaction between upper and lower-level potential vorticity anomalies. We suggest that a checklist with stepwise indicators responsible for development be prepared for the forecasting of heavy snowfall over the southwestern part of the Korean Peninsula.
文摘A total of 61 supercells with mesocyclones lasting for at least 6 volume scans were investigated. These storm parameters and mesocyclone parameters were counted and compared to determine the salient differences between isolated supercells and embedded supercells in different regions. The results showed that the mesocyclone parameters had different evolution characteristics in three stages of mesocyclone. The storm parameters, mesocyclone parameters and severe weather phenomenon had significantly differences between isolated supercells and embedded supercells. The mesocyclone parameter differences determined the differences in the reflectivity structure and weather phenomenon. The higher base and top of mesocyclone for isolated supercells indicated that the isolated supercells had higher maximum reflectivity, maximum reflectivity height, cell-based vertically integrated liquid and top of storm cell, and significantly higher probability of hail or large hail than the embedded supercells. The descending lower base of mesocyclone at its mature stage in the region of Jianghuai Plain indicated that the supercells in this region had a higher probability of mesocyclone-induced tornado.
基金supported by the National Key R&D Program of China(2022YFC3004101)the National Natural Science Foundation of China(Grant No.42275006)+2 种基金the Guangdong Basic and Applied Basic Research Foundation(Grant No.2022A1515011814)the China Meteorological Administration Tornado Key Laboratory(Grant No.TKL202302)the Science and Technology Research Project of Guangdong Meteorological Service(Grant No.GRMC2023Q35)。
文摘This study presents finely resolved radar signatures of multiple cyclonic vortices associated with an EF2 tornadic supercell that occurred in Guangzhou on 16 June 2022 and discusses how the mesocyclone formed on the lee side of mountain.A nearby X-band phased-array radar provides evidence that the mesocyclone was shallow,with a depth generally confined to less than 3 km.The mesocyclonic feature was observed to initiate from near-ground level,driven by the interaction between intensifying cold pool surges and shallow lee-side ambient flows.It was first recognized shortly after the presence of near-ground cyclonic convergence signatures over the leading edges of cold pool outflows.Over the subsequent 17 min,the mesocyclone developed upward,reaching a maximum height of 3 km,and produced a tornado 8min later.Nearly coinciding with the time of tornadogenesis,a noticeable separation of the low-level tornado cyclone from the midlevel mesocyclone was observed.This shift in the vertically oriented vortex tube was likely caused by modifications to the low-level flow due to the complex hilly terrain or by occlusions associated with rear-flank downdrafts.After tornadogenesis,high-resolution X-PAR observations revealed that the lowest-level mesocyclonic signature contracted into a gate-to-gate tornadic vortex signature(TVS)at the tip of hook echoes.Compared to conventional S-band operational weather radars,rapid-scan X-PAR observations indicate that a core diameter threshold of 1.5–2 km could be employed to identify a cyclonically sheared radial velocity couplet as a TVS,potentially extending the lead time for Doppler-based tornado warnings.
基金Supported by the National Natural Science Foundation of China under Grant Nos.40505004,40405012,and 40333025the National Grand Fundamental Research 973 Program of China(973:2004CB418301)+1 种基金the GYHY(QX) 200706033and the NMCTIGGE Program GYHY(QX) 2007-232 6-1.
文摘In this study, the kinematic and precipitation structures of a mesocyclone associated with a hook echo were analyzed using single Doppler radar data. The mesocyclone was embedded in a mesoscale convective rainband near northern Taiwan coastline on 10 September 2004. The synoptic environment was characterized by a moderate convective available potential energy （CAPE） and a moderate ambient vertical shear from surface to 5 km. In addition, a pronounced low-level mesoscale shear/convergence zone, which resulted from the interaction of two tropical depressions, was also identified in the northwest coast of Taiwan, providing a favorable dynamic condition for the development of the mesocyclone. Analyzing single Doppler dipole signature shows that this mesocyclone formed initially at low levels, then deepened and strengthened rapidly into mature stage with the vertical depth exceeding 8 km. The diameter of the mesocyclone decreased with the height at the time of vortexgenesis, and then evolved into columnar structure accompanied with the broader diameter in middle layer. The mesocyclone lasted for about 2 h. The Ground-Based Velocity Track Display （GBVTD） method was applied to retrieve the ax- isymmetric circulation of the mesocyclone. The GBVTD-derived primary circulation showed the radius of maximum wind （RMW） of the mesocyclone was about 5-6 km and varied from inward tilting to outward tilting with time. The axisymmetric radial wind field was initially characterized by a low-level inflow inside the RMW and outflow outside the RMW, respectively. The strongest reflectivity was associated with a stronger updraft near the RMW, and a weak downdraft was located at the center of the mesocyclone. Subsequently the downdraft and reflectivity near the mesocyclone center strengthened obviously, accompanied with the low-level outflow, strong updraft as well as high reflectivity extending outside the RMW. The relative tangential wind initially exhibited a wavenumber 1 asymmetric structure with the maximum wind region at the left portion of the meso cyclone and shifted counterclockwise with height. The axisymmetric tangential wind strengthened and reached its maximum intensity with a value about 20 m s^-1 at z=1 km. After that the axisymmetric tangential wind decreased rapidly, meanwhile the wave-1 asymmetric structure redeveloped with the maximum wind at the left-front of motion. In summary, the evolution and structure of the mesocyclone is similar to that observed within a non-supercell mesocyclone. It is worth to mention that the axisymmetric circulation characteristics of the mesocyclone at its mature stage are very similar to those observed in a mature typhoon. However, there are significant differences, i.e., the size is much smaller, the lifetime is much shorter, and the downdraft in the center is produced by precipitation instead of compensating subsidence.
基金National Key R&D Program of China (2022YFC3004101)Science and Technology Projects of Guangzhou (2023B04J0704,2023B04J0232)+1 种基金Natural Science Foundation of Guangdong Province (2022A15150118141)Key Scientific and Technological Research Project of Guangzhou Meteorological Society (Z202201)。
文摘The X-band phased array radar offers faster scanning speed and higher spatial resolution compared to the S-band radar,making it capable of enhancing tornado monitoring and early warning capabilities.This study analyzed the characteristics and nowcasting signals of a tornado case that occurred on June 16,2022 in the Guangzhou region.Our findings indicate that the violent contraction of rotation radius and the dramatic increase in rotation speed were important signal characteristics associated with tornado formation.The X-band phased array radar,with its high temporal and spatial resolution,provided an opportunity to capture early warning signals from polarimetric characteristics.The X-band phased array radar demonstrated noteworthy ability to identify apparent tornado vortex signature(TVS)features in a 10-minute lead time,surpassing the capabilities of the CINRAD/SA radar.Additionally,due to its higher scanning frequency,the Xband phased-array radar was capable of consistently identifying TVS with shorter intervals,enabling a more precise tracking of the tornado's path.The application of professional radars,in this case,provides valuable insights for the monitoring of evolutions of severe local storms and even tornadoes and the issuance of early warning signals.
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.
文摘Hurricane Ida ferociously affected many south-eastern and eastern parts of the United States,making it one of the strongest hurricanes in recent years.Advanced forecast and warning tool has been used to track the path of the ex-Hurricane,Ida,as it left New Orleans on its way towards the northeast,accurately predicting significant supercell development above New York City on September 01,2021.This advanced method accurately detected the area with the highest possible level of convective instability with 24-h lead time and even Level 5,devised in the categorical outlooks legend of the system.Therefore,an extreme level implied a very high probability of the local-scale hazard occurring above the NYC.Cloud model output fields(updrafts and downdrafts,wind shear,near-surface convergence,the vertical component of relative vorticity)show the rapid development of a strong supercell storm with rotating updrafts and a mesocyclone.The characteristic hook-shaped echo signature visible in the reflectivity patterns indicates a signal for a highly precipitable(HP)supercell with the possibility of tornado initiation.Open boundary conditions represent a good basis for simulating a tornado that evolved from a supercell storm,initialized with initial data obtained from a real-time simulation in the period when the bow echo and tornado-like signature occurred.Тhe modeled results agree well with the observations.
基金Supported by the National Special Fund for Meteorology(GYHY200706033)National Natural Science Foundation of China under Grant Nos.40505004,40405012,and 40333025+1 种基金National Fundamental Research"973"Program of China(2004CB418301) the Natioual Meteorological Center of China TIGGE Program(GYHY(QX) 2007-232 6-1)
文摘In this study,single Doppler radar data were used to examine the structure and evolution of a high precipitation（HP） supercell embedded in a cold front near Jianyang,Fujian Province on 12 April 2003.The synoptic environment was characterized by high humidity at low levels,moderate CAPE（convective available potential energy;1601 J kg^（-1））,moderate wind shear（22 m s^（-1） in 0-5 km）,and veering of the horizontal winds with height,similar to those HP supercells previously observed in midlatitudes.In addition,the calculated bulk Richardson number was only 16,suggesting favorable environmental conditions for supercell development. The documented storm was located at the leading edge of a squall line.It was initiated from a single cell at 0732 UTC.It evolved into a bow shape gradually,and then split into two separate storms along the storm motion direction through the apex of the bow echo.The left-moving storm dissipated rapidly, but the right-moving storm strengthened and evolved into an HP supercell,lasting for more than 1 h.The radar reflectivity of the HP supercell during its mature stage showed a typical low-level hook echo at the front flank of the storm with its maximum reflectivity beyond 70 dBZ.Above the hook echo,an elevated maximum reflectivity core accompanied by a bounded weak-echo region（BWER） and a down-shear echo overhanging aloft were clearly identified.The elevated BWER,marked by 40-50-dBZ reflectivity values,was surrounded by values of 60-70 dBZ.A well-defined mesocyclone lasted about 1 h and was collocated with the low-level WER and middle-level BWER.The radar-estimated time-height profiles of mesocyclone rotational velocity and diameter indicated that this mesocyclone formed initially at middle level,then deepened and strengthened rapidly with the vertical depth deeper than 8 km and rotational velocity stronger than 24 m s^（-1） at the mature stage,and later decayed rapidly.The GBVTD（ground-based velocity track display）-derived primary circulation showed that the maximum tangential wind of the mesocyclone appeared at middle level （3-5 km） with a value of about 20 m s^（-1）.The mean radial wind field was characterized with a low-level inflow below 4 km,and accompanied by stronger updraft near the mesocyclone center.Between 4 and 7 km.the tangential wind profile resembled a Rankine combined vortex with the radius of maximum wind （RMW） at 3 km.and there was outflow/inflow inside/outside of the RMW.Correspondingly,the vertical velocity indicated a stronger updraft at the RMW and a weak downdraft inside the RMW.Above 7 km,the outflow strengthened and extended outside the RMW. In summary,the reflectivity structures of the storm and the accompanying mesocyclone were similar to those midlatitude HP supercells proposed in Miller＇s paper in 1994.However,the evolution of the HP supercell,including its three stages：ordinary storm,bow echo,and storm splitting,was quite different from those documented before.
基金Supported by the National Natural Science Foundation of China under Grant No. 40575012Department of Science and Technology of Shandong Province under Grant No. 2007GG20008001
文摘Three supercell storms on 24 June 2004（0624）,28 June 2003（0628）,and 27 September 2002（0927） induced different damages in Shandong Province.Storm 0927 was inferior in size and intensity to storms 0628 and 0624.The structure and evolvement of the three storms were analyzed in detail based on the WSR98D radar data in combination with weather charts.The results show that mesoscale surface convergence triggered release of instable energy,which resulted in severe convection.During the development stage,storms 0927,0628,and 0624 displayed multi-cell propagation,single-cell evolution,and multi-cell mergence,respectively.The storm tracks were similar：they were all right-moving supercell storms,i.e.,moving at an angle of 30°-70° to the right of the mean wind and at a speed of about 45%-70% of the mean wind speed.In the mature stage,the maximum reflectivity appeared at the low level in storm 0927,mid level in storm 0628,and mid-upper level in storm 0624.These storms possessed almost all typical features of supercell storms：weak echo region（WER）,bounded weak echo region（BWER）,and mesocyclone.An organized mesocyclone formed at the middle height of an updraft,deepened gradually downward and upward,and became a typical mid-level mesocyclone with strong updrafts.The vertical structures of airflows in the three storms were similar,i.e.,significant convergence at low level,nearly pure rotation at mid level,and divergent rotation at upper level.However,signatures of mid-level horizontal airflows in the three storms were different：at mid level,there was a single vortex in storm 0628,but a double-vortex flow pattern was seen in storms 0927 and 0624.The horizontal structure of the double-vortex flow was hard to be blown away by the environmental airflow,and thus the storms could persist for a longer period of time than the single vortex storm.
基金Supported by the National Natural Science Foundation of China(42275006 and 42305002)Guangdong Basic and Applied Basic Research Foundation(2024A1515510006)+2 种基金China Meteorological Administration Tornado Key Laboratory(TKL202302)Guangdong-Hong Kong-Macao Greater Bay Area(GBA)Meteorological Science and Technology Collaborative Research Project(GHMA2024Z03)Guangdong Meteorological Administration Research Project(GRMC2023M47)。
文摘The understanding of unusual supercell outbreaks remains limited.This study examines the development and environmental conditions of a supercell outbreak event that occurred on 26 March 2022,when 19 supercells formed within just 6 h in the coastal region of southern China.The focus is on analyzing radar characteristics and highlighting the role of a surface cold front in driving the development of rotating storms.The cold front created significant variations in low-level vertical wind shear and conditional instability on its warm and cool sides.Most of the 19 supercells formed along the front or on its adjacent cool side.Both observations and simulations reveal that favorable dynamic conditions for supercell development appeared and concentrated in a relatively narrow area on the cool side of the front,influenced by directional wind shear near the surface,which drove the formation and positioning of supercells.Numerical simulations demonstrate that the supercells developed their rotating updrafts upon encountering the 2-4-km scale misocyclones located at the convergent boundary of the cold front.The rotating storms were enhanced when they traversed the intersection zone created by the cold front and convergent boundaries under the influence of the unique land-sea contrast of the Pearl River Delta.In sum,appropriate dynamic allocation of wind shear,cold front,and landform has facilitated development of the clustered supercell outbreak.These findings may offer valuable insights on improving severe weather forecasts in this tornado-prone area.
