Based on previously released data,this paper first presented the criteria for recognizing bow echoes and divided their life cycle into three stages:the development stage,the mature stage,and the attenuation stage.Base...Based on previously released data,this paper first presented the criteria for recognizing bow echoes and divided their life cycle into three stages:the development stage,the mature stage,and the attenuation stage.Based on Doppler weather radar data during 2011-2020,43 bow echo events(including 54 individual bow echoes)in western South China were identified.The spatial and temporal distributions,formation and dissipation modes of these bow echoes,and the severe weather they caused were statistically analyzed.The results show that:(1)The bow echo events were unevenly distributed year-to-year,but all occurred from March to July,with the highest in April and May and the lowest in July.The period from night to early morning was found to be the main period for bow echo generation and intensification.(2)A banded area from Hechi City on the southeastern edge of the Yunnan-Guizhou Plateau to Wuzhou City in southeast Guangxi was identified as a high-incidence area of bow echoes.The length of bow echoes was correlated with their life cycle.(3)The origins of the bow echoes could be divided into five locations,most of which were in the eastern Yunnan-Guizhou Plateau.After entering western South China,their moving paths were categorized into three types,among which most bow echoes moved southeastward,generally because of the effect of cold air.Specifically,bow echoes generally moved eastward when cold air was weak or in the warm zone.Meanwhile,the fewest bow echoes moved northeastward.(4)Four modes of bow echo formation were identified:linearly organized,broken areal,linearly merging,and broken line.Dissipation could also be classified into four types.(5)The probability of convective weather generated by a bow echo was largest in the mature stage.展开更多
A bow echo is a type of mesoscale convective phenomenon that often induces extreme weather and appears with strong reflectivity on radar images. A strong bow echo that developed from a supercell was observed over Fosh...A bow echo is a type of mesoscale convective phenomenon that often induces extreme weather and appears with strong reflectivity on radar images. A strong bow echo that developed from a supercell was observed over Foshan City in southern China on 17 April 2011. The intense gusty winds and showers caused huge losses of property and severely affected human lives. This paper presents an analysis of this strong meso- n-scale convective system based on Doppler radar observations. The isolated bow echo exhibited a horizontal scale of about 80 km in terms of reflectivity above 40 dBZ, and a life span of 8 hours. The system originated from the merging of a couple of weakly organized cells in a shear line, and developed into an arch shape as it moved through the shear zone. Sufficient surface moisture supply ensured the convective instability and development of the bow echo. The low-altitude winds retrieved from single Doppler radar observations showed an obvious rear-inflow jet along the notch area. Different from the conventional definition, no book- end anticyclone was observed throughout the life cycle. Very strong slantwise updrafts and downdrafts were recognizable from the retrieved winds, even though the spatial scale of the bow echo was small. Strong winds and induced damage on the surface are considered to have been caused by the mid-level rear-inflow jet and intense convective downdrafts.展开更多
Observational analyses and convection-permitting simulations are conducted to study an extreme event of damaging surface winds within a bow-shaped squall line over South China.Prevailing explanations for the formation...Observational analyses and convection-permitting simulations are conducted to study an extreme event of damaging surface winds within a bow-shaped squall line over South China.Prevailing explanations for the formation of damaging surface winds were applied to investigate the detailed processes at the mature stage of a squall line in a complicated real-world scenario.It is shown that environmental vertical wind shear was adequately strong to cause a shearing vorticity,and the shearing vorticity was comparable to the baroclinic vorticity by a cold pool.The balance led to strong upward motions at the leading edge of the squall line and brought plenty of rainfall.The descending rainfall cooled the surrounding air and entrained the upper-level cold air downward to the lower level,strengthening the cold pool by excessive evaporation and melting.The cold pool accelerated the propagation speed of the squall line and caused extensive wind damage at the surface.Meanwhile,the horizontal vortex lines at the leading edge of the cold pool were lifted by frontal updrafts and tilted to form the anti-cyclonic vortex at the middle level.This maintained and intensified the rearinflow jet behind the apex of bow echo in association with a notable midlevel pressure gradient.The rear-inflow jet was then transported downward to the surface by descending condensate,leading to damaging winds there.Other factors,such as environmental flows,however,contributed less to the damaging surface winds.展开更多
基金National Natural Science Foundation of China(52239006,41975001,41930972)Natural Science Foundation of Guangxi Zhuang Autonomous Region(2022GXNSFBA035565)。
文摘Based on previously released data,this paper first presented the criteria for recognizing bow echoes and divided their life cycle into three stages:the development stage,the mature stage,and the attenuation stage.Based on Doppler weather radar data during 2011-2020,43 bow echo events(including 54 individual bow echoes)in western South China were identified.The spatial and temporal distributions,formation and dissipation modes of these bow echoes,and the severe weather they caused were statistically analyzed.The results show that:(1)The bow echo events were unevenly distributed year-to-year,but all occurred from March to July,with the highest in April and May and the lowest in July.The period from night to early morning was found to be the main period for bow echo generation and intensification.(2)A banded area from Hechi City on the southeastern edge of the Yunnan-Guizhou Plateau to Wuzhou City in southeast Guangxi was identified as a high-incidence area of bow echoes.The length of bow echoes was correlated with their life cycle.(3)The origins of the bow echoes could be divided into five locations,most of which were in the eastern Yunnan-Guizhou Plateau.After entering western South China,their moving paths were categorized into three types,among which most bow echoes moved southeastward,generally because of the effect of cold air.Specifically,bow echoes generally moved eastward when cold air was weak or in the warm zone.Meanwhile,the fewest bow echoes moved northeastward.(4)Four modes of bow echo formation were identified:linearly organized,broken areal,linearly merging,and broken line.Dissipation could also be classified into four types.(5)The probability of convective weather generated by a bow echo was largest in the mature stage.
基金supported by the National Basic Research Program of China(Grant No.2012CB417204)National Natural Science Foundation of China projects(Grant Nos.41175095 and 40875065)partly by the National Key Technology R&D Program(Grant No.2012BAC22B01)
文摘A bow echo is a type of mesoscale convective phenomenon that often induces extreme weather and appears with strong reflectivity on radar images. A strong bow echo that developed from a supercell was observed over Foshan City in southern China on 17 April 2011. The intense gusty winds and showers caused huge losses of property and severely affected human lives. This paper presents an analysis of this strong meso- n-scale convective system based on Doppler radar observations. The isolated bow echo exhibited a horizontal scale of about 80 km in terms of reflectivity above 40 dBZ, and a life span of 8 hours. The system originated from the merging of a couple of weakly organized cells in a shear line, and developed into an arch shape as it moved through the shear zone. Sufficient surface moisture supply ensured the convective instability and development of the bow echo. The low-altitude winds retrieved from single Doppler radar observations showed an obvious rear-inflow jet along the notch area. Different from the conventional definition, no book- end anticyclone was observed throughout the life cycle. Very strong slantwise updrafts and downdrafts were recognizable from the retrieved winds, even though the spatial scale of the bow echo was small. Strong winds and induced damage on the surface are considered to have been caused by the mid-level rear-inflow jet and intense convective downdrafts.
基金Research(2020B0301030004)National Natural Science Foundation of China(42275002)+3 种基金Natural Science Foundation of Chongqing(CSTB2022NSCQ-MSX0890)Scientific and Technological Project of Chongqing Meteorological Service(YWJSGG-202124)Key Innovation Team of China Meteorological Administration(CMA2022ZD09)Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)(SML2023SP209)。
文摘Observational analyses and convection-permitting simulations are conducted to study an extreme event of damaging surface winds within a bow-shaped squall line over South China.Prevailing explanations for the formation of damaging surface winds were applied to investigate the detailed processes at the mature stage of a squall line in a complicated real-world scenario.It is shown that environmental vertical wind shear was adequately strong to cause a shearing vorticity,and the shearing vorticity was comparable to the baroclinic vorticity by a cold pool.The balance led to strong upward motions at the leading edge of the squall line and brought plenty of rainfall.The descending rainfall cooled the surrounding air and entrained the upper-level cold air downward to the lower level,strengthening the cold pool by excessive evaporation and melting.The cold pool accelerated the propagation speed of the squall line and caused extensive wind damage at the surface.Meanwhile,the horizontal vortex lines at the leading edge of the cold pool were lifted by frontal updrafts and tilted to form the anti-cyclonic vortex at the middle level.This maintained and intensified the rearinflow jet behind the apex of bow echo in association with a notable midlevel pressure gradient.The rear-inflow jet was then transported downward to the surface by descending condensate,leading to damaging winds there.Other factors,such as environmental flows,however,contributed less to the damaging surface winds.
