Fires,including wildfires,harm air quality and essential public services like transportation,communication,and utilities.These fires can also influence atmospheric conditions,including temperature and aerosols,potenti...Fires,including wildfires,harm air quality and essential public services like transportation,communication,and utilities.These fires can also influence atmospheric conditions,including temperature and aerosols,potentially affecting severe convective storms.Here,we investigate the remote impacts of fires in the western United States(WUS)on the occurrence of large hail(size:≥2.54 cm)in the central US(CUS)over the 20-year period of 2001–20 using the machine learning(ML),Random Forest(RF),and Extreme Gradient Boosting(XGB)methods.The developed RF and XGB models demonstrate high accuracy(>90%)and F1 scores of up to 0.78 in predicting large hail occurrences when WUS fires and CUS hailstorms coincide,particularly in four states(Wyoming,South Dakota,Nebraska,and Kansas).The key contributing variables identified from both ML models include the meteorological variables in the fire region(temperature and moisture),the westerly wind over the plume transport path,and the fire features(i.e.,the maximum fire power and burned area).The results confirm a linkage between WUS fires and severe weather in the CUS,corroborating the findings of our previous modeling study conducted on case simulations with a detailed physics model.展开更多
[Objective] The Doppler radar data about a super monomer hailstorms in the northeastern Qinghai-Tibet Plateau in the Zhongchuan Airport in the Lanzhou City on September 6,2010 was studied.[Method] By dint of routine d...[Objective] The Doppler radar data about a super monomer hailstorms in the northeastern Qinghai-Tibet Plateau in the Zhongchuan Airport in the Lanzhou City on September 6,2010 was studied.[Method] By dint of routine data and radar data,the low vortex shear line type and the super monomer hailstorm around the Zhongchuan Airport in the Lanzhou City on September 6,2010 were expounded.Basic product and secondary product of Doppler radar were used in this process to reflect the characteristics of strong convection weather.Some characteristics of this process shall be explored.[Result] A small gush of cold air from the cold vortex of 500 hPa in the middle and high layer provided impacts.The warm shear line provided water vapor and energy in the 700 hPa.There was strong convective weather in the upper air.Such 10 minutes of hailstorm was rarely seen in the drought land in the northwest.The characteristics of the strong convection were distinct and typical.The front showed no echo form.However,it can not be reflected in 'strong wedge' in another form.In this process,characteristics of BWER and middle scale cyclone were distinct.And this was a typical hailstorm process caused by super monomer.[Conclusion] The study provided some helpful references for the forecast of strong convection weather in the Zhongchuan Airport in Lanzhou City.展开更多
By their definition, destructive hailstorms cause a great deal of damage to property and have been known to be fatal to humans. At present the long term changes in the frequency of these storms are unknown. Records of...By their definition, destructive hailstorms cause a great deal of damage to property and have been known to be fatal to humans. At present the long term changes in the frequency of these storms are unknown. Records of destructive hailstorms from many different sources in England and Wales go back for several centuries. Recently discovered records of over 30 destructive hailstorms have allowed a better description of hailstorm history since 1780. The data were grouped into 30, 40, and 50 year non-overlapping time periods in relation to time. Increases in their frequency in the 17th and 18th centuries were probably due to an increase in population and better recording. Since 1900 the frequency has significantly declined so that in the present 50 year time period only 22 have been recorded as compared with an average of 49 in both halves of the 19th century. The decline in frequency may be partly due to the big increase in particulate matter from aviation, which leads to a much higher concentration of ice and cloud condensation nuclei, resulting in fewer destructive hailstorms.展开更多
The growth trajectory of hailstones within clouds has remained elusive due to the inability to trace them directly,impeding the comprehension of their underlying growth mechanisms.This study investigated hailstone ver...The growth trajectory of hailstones within clouds has remained elusive due to the inability to trace them directly,impeding the comprehension of their underlying growth mechanisms.This study investigated hailstone vertical growth trajectories by detecting the stable isotope signatures(2H and 18O compositions)of different shells in 27 hailstones from 9hailstorms,which allowed us to capture the ambient temperature during hailstone growth.The vertical growth trajectories were obtained by comparing the isotopic compositions of water condensate in clouds,derived from the Adiabatic Model,with those measured in hailstones.Although hailstone growth was primarily observed in the–10°C to–30°C temperature layer,the embryo formation height and subsequent growth trajectories significantly varied among hailstones.Embryos formed over a wide range of temperatures(–8.7°C to–33.4°C);four originated at temperatures above–15°C and 16originated at temperatures below–20°C,suggesting ice nuclei composed of bioproteins and mineral dust,respectively.Among the 27 measured hailstones,3 exhibited minimal vertical movement,16 exhibited a monotonic rise or fall,and the remaining 8 exhibited alternating up-down trajectories;only one experienced“recycling”during up-down drifting.Trajectory analysis revealed that similar-sized hailstones from a single storm tended to form at similar heights,whereas those larger than 25 mm in diameter exhibited at least one period of upward growth.Vertical trajectories derived from isotopic analysis were corroborated by radar hydrometeor observations.展开更多
By using the cloud-to-ground (CG) lightning location data from the lightning detection network of He- nan Province, surface Doppler radar data and standard orbit data of PR, TMI and LIS on TRMM satellite, the spatial ...By using the cloud-to-ground (CG) lightning location data from the lightning detection network of He- nan Province, surface Doppler radar data and standard orbit data of PR, TMI and LIS on TRMM satellite, the spatial and temporal characteristics of CG lightning flashes in 10 severe hailstorms are analyzed. The results show that the percentage of +CG lightning in these hailstorms is high with an average value of 45.5%. There is a distinct increase in CG flash rate during the rapid development stage of hailstorms. The hailstone falling corresponds to an active positive flash period, and the increase of +CG flash rate is generally accompanied with a decrease of –CG flash rate. The flash rate declines rapidly during the dissipating stage of hailstorms. The precipitation structure and lightning activity in two typical hail- storms are studied in detail. It is found that strong convective cells with reflectivity greater than 30dBZ mainly are situated in the front region of hailstorms, whereas the trailing stratiform region is in the rear part of the hailstorms. The maximum heights of echo top are higher than 14 km. Convective rain con- tributes much more rainfall to the total than stratiform rain, and the convective rain takes about 85% and 97% of the total in the two cases, respectively. Total lightning in the hailstorms is very active with the flash rate up to 183 fl/min and 55 fl/min, respectively. The results also indicate that most lightning flashes occurred in the echo region greater than 30 dBZ and its immediate periphery. The probability of lightning occurrence is 20 times higher in the convective region than in the stratiform region. The result suggests that the lightning information is helpful to the identification of convective rain region. The linear relationship between flash rate and ice water content is disclosed primarily.展开更多
Two hailstorms that occurred in Beijing and Tianjin,respectively,are investigated,based mainly on the total lightning data observed by the System d＇Alerte Fondre par Interferometric Radioelecctrique（SAFIR3000）,the ...Two hailstorms that occurred in Beijing and Tianjin,respectively,are investigated,based mainly on the total lightning data observed by the System d＇Alerte Fondre par Interferometric Radioelecctrique（SAFIR3000）,the cloud-to-ground（CG） lightning data of a CG lightning location system,and the echo data of a Doppler radar.Both hailstorms exhibited two lightning frequency peaks：the first was before the hailfall and the second was after the hailfall,with the second peak greater than the first.The dominant polarity of the CG lightning was positive in the stage around the first frequency peak,but changed to negative in the stage around the second frequency peak.The evolution of radar echoes and the height distribution of lightning radiation sources are explored,revealing that both hailstorms had stronger convection and the main positive charge occurred at mid levels during the stage around the first frequency peak.However,whilst the Beijing hailstorm experienced the enhancement of convection,with the main positive charge at upper levels around the second frequency peak,the Tianjin hailstorm generated its second frequency peak during the period when the convection kept weakening and the main positive charge dropped to mid-lower levels.Through evaluation of the radar parameters,we investigate the mechanisms responsible for the second stage of active lightning discharge.Furthermore,the lightning activity exhibited a close relationship with radar echo parameters and hailfall.Lightning jump signals were found before the hailfall and were associated with the change ratio of the 40-dBZ echo volume above the-15℃ level,which demonstrates the application value of lightning data in severe weather warning.展开更多
A shower cloud observed in Jiangxi,a hailstorm observed in Hebei and“75.8”torrential rain in Henan are simulated with our microphysical model in a one-dimensional framework.The model,using the radio- sonde data as i...A shower cloud observed in Jiangxi,a hailstorm observed in Hebei and“75.8”torrential rain in Henan are simulated with our microphysical model in a one-dimensional framework.The model,using the radio- sonde data as input,gets its output which shows agreement in many aspects as compared with observations in each case.The glaciation of small cumulus cloud,low precipitation efficiency of hailstorm and the per- sistence of torrential rain are demonstrated.It is also shown that the Bergeron process has little influence, but the warm-rain process plays an important role in the formation of precipitation in cumulonimbus with a warm cloud base.展开更多
There were three hailstorms in Shandong Province, caused by a same northeast cold eddy situation on 1 June 2002. Cloud-to-ground （CG） flashes occurring in the weather event were observed by Shandong Lightning Detect...There were three hailstorms in Shandong Province, caused by a same northeast cold eddy situation on 1 June 2002. Cloud-to-ground （CG） flashes occurring in the weather event were observed by Shandong Lightning Detection Network （SLDN）, which consists of 10 sensors covering all over Shandong Province. The temporal and spatial distributions of CG lightning are investigated for the three hailstorms by using the data from SLDN, Doppler radar and satellite. The results show that different thunderstorms present different lightning features even if under the same synoptic situation. The percentage of positive CG lightning is very high during the period of hail falling. CG flashes mainly occurred in the region with a cloud top brightness temperature lower than -50℃. Negative CG flashes usually clustered in the lower temperature region and tended to occur in the region with maximum temperature gradient, while the positive ones usually spread discretely. Negative CG flashes usually occurred in intense echo regions with reflectivity greater than 50 dBz, while the positive CG flashes often occurred in weak and stable echo regions （10-30 dBz） or cloud anvils, although they can be observed in strong convective regions sometimes. Almost all haft falling took place in the stage with active positive flashes, and the peak positive flash rate is a little prior to the hail events. The thunderstorm could lead to disastrous weather when positive CG lightning activities occur in cluster. Severe thunderstorms sometimes present a low flash rate at its vigorous stage, which is probably caused by the ＂mechanism of chargeregion lift＂ through investigating the reflectivity evolution. Combined with the total lightning （intracloud and CG） data obtained by LIS onboard TRMM, the phenomenon of high ratio of intracloud flash to CG flash in severe hailstorm has been discussed. The competition of the same charge sources between different lightning types can also be helpful for explaining the cause of low CG lightning activities in severe storms.展开更多
In this paper, a hailstorm occurring on 9 May 1999 in Huanghuai region was studied by using the combined data from the precipitation radar （PR）, microwave image （TMI）, and visible infrared scanner （VIRS） on the ...In this paper, a hailstorm occurring on 9 May 1999 in Huanghuai region was studied by using the combined data from the precipitation radar （PR）, microwave image （TMI）, and visible infrared scanner （VIRS） on the Tropical Rainfall Measuring Mission （TRMM） satellite. According to the 3-orbit observations of 5- h duration from the TRMM satellite, the variation characteristics of the precipitation structures as well as cloud top temperature and microwave signals of the precipitating cloud were comprehensively analyzed during the evolution of hailstorm. The results show that the precipitation is obviously converted from early hail cloud with strong convection into the later storm cloud with weak convection. For hail cloud, there exists some strong convective cells, and the heavy solid precipitation is shown at the middle-top levels so that the contribution of rainfall amount above the freezing-layer to the column precipitation amount is rather larger than that within the melting-layer. However, for storm cloud, the convective cells are surrounded by the large area of stratiform precipitation, and the precipitation thickness gradually decreases, and the rainfall above the freezing-layer obviously reduces and the contribution of rainfall amount within the melting-layer rapidly increases. Therefore, the larger ratio of rainfall amount above the freezing layer to column precipitation amount is, the more convective the cloud is; reversely, the larger proportion of rainfall below the melting layer is, the more stable the stratiform cloud is. The different changing trends of microwave signals at different precipitation stages show that it is better to consider the structures and stages of precipitating cloud to choose the optimal microwave channels to retrieve surface rainfall.展开更多
The Regional Atmospheric Modeling System (RAMS) has been used to investigate the effects of varied giant cloud condensation nuclei (GCCN) concentrations on precipitation characteristics of the spring hailstorms in a s...The Regional Atmospheric Modeling System (RAMS) has been used to investigate the effects of varied giant cloud condensation nuclei (GCCN) concentrations on precipitation characteristics of the spring hailstorms in a semi-arid region. The simulation result shows that this variation has significant effects on the storm microphysical processes as well as on the surface precipitation. The coverage of hail and hail mixing ratio maxima in cloud increases with greater GCCN concentrations. The accumulation zone structure benefits the growth of hail particles. Higher GCCN concentrations lead to more supercooled rain water and cloud water available for freezing. This simulation also shows that increasing GCCN concentrations may produce more rainfall on the surface but less hail precipitation, and the total accumulated precipitation increases while the ice phase precipitation decreases. This effect is stronger in polluted air than in clean air. The surface flow field changes with different GCCN concentrations. The identification index of spring hailstorm is different from that of summer hailstorm with a different aerosol background.展开更多
During a hailstorm event,near-surface meso-γvortices along a convergence line interact with hail cells.Herein we investigate this interaction by using observational data and a high-resolution simulation of a hailstor...During a hailstorm event,near-surface meso-γvortices along a convergence line interact with hail cells.Herein we investigate this interaction by using observational data and a high-resolution simulation of a hailstorm that occurred over Taizhou(Zhejiang,China)on 19 March 2014.The 10-m surface wind data from automatic weather stations show that several meso-γvortices or vortex-like disturbances existed over the convergence zone and played a vital role in the evolution of the hailstorm and the location of the hail.The model results agree with the observations and present a closer correlation between the hail and the low-level meso-γvortices than those observed.The model simulation indicates that such low-level meso-γvortices can be used to predict the next 10-min hail fallout zone.The lowlevel meso-γvortices originated over the convergence zone and then fed back into the convergence field and provoked a stronger updraft.Vorticity was initiated primarily by stretching and was extended by tilting.A three-dimensional(3-D)flow analysis shows that the existence of low-level meso-γvortices could help enhance a local updraft.Furthermore,the simulation reveals that the low-level meso-γvortices formed in the bounded weak echo region(WER)at the front of the hail cell,enhancing convergence and strengthening updrafts.Graupel was broadly located between the 0°C isothermal line and the top of the clouds,roughly between the 0 and-20°C isothermal lines.Accordingly,the hailstones grew rapidly.The suitable environment and the positive effect of the meso-γvortices on the updrafts enabled hailstorm formation.展开更多
基金supported by the U.S.Department of Energy,Office of Science,Office of Biological and Environmental Research program as part of the Regional and Global Model Analysis and Multi-Sector Dynamics program areas(Award Number DE-SC0016605)Argonne National Laboratory is operated for the DOE by UChicago Argonne,LLC,under contract DE-AC02-06CH11357+1 种基金the National Energy Research Scientific Computing Center(NERSC)NERSC is a U.S.DOE Office of Science User Facility operated under Contract DE-AC02-05CH11231.
文摘Fires,including wildfires,harm air quality and essential public services like transportation,communication,and utilities.These fires can also influence atmospheric conditions,including temperature and aerosols,potentially affecting severe convective storms.Here,we investigate the remote impacts of fires in the western United States(WUS)on the occurrence of large hail(size:≥2.54 cm)in the central US(CUS)over the 20-year period of 2001–20 using the machine learning(ML),Random Forest(RF),and Extreme Gradient Boosting(XGB)methods.The developed RF and XGB models demonstrate high accuracy(>90%)and F1 scores of up to 0.78 in predicting large hail occurrences when WUS fires and CUS hailstorms coincide,particularly in four states(Wyoming,South Dakota,Nebraska,and Kansas).The key contributing variables identified from both ML models include the meteorological variables in the fire region(temperature and moisture),the westerly wind over the plume transport path,and the fire features(i.e.,the maximum fire power and burned area).The results confirm a linkage between WUS fires and severe weather in the CUS,corroborating the findings of our previous modeling study conducted on case simulations with a detailed physics model.
文摘[Objective] The Doppler radar data about a super monomer hailstorms in the northeastern Qinghai-Tibet Plateau in the Zhongchuan Airport in the Lanzhou City on September 6,2010 was studied.[Method] By dint of routine data and radar data,the low vortex shear line type and the super monomer hailstorm around the Zhongchuan Airport in the Lanzhou City on September 6,2010 were expounded.Basic product and secondary product of Doppler radar were used in this process to reflect the characteristics of strong convection weather.Some characteristics of this process shall be explored.[Result] A small gush of cold air from the cold vortex of 500 hPa in the middle and high layer provided impacts.The warm shear line provided water vapor and energy in the 700 hPa.There was strong convective weather in the upper air.Such 10 minutes of hailstorm was rarely seen in the drought land in the northwest.The characteristics of the strong convection were distinct and typical.The front showed no echo form.However,it can not be reflected in 'strong wedge' in another form.In this process,characteristics of BWER and middle scale cyclone were distinct.And this was a typical hailstorm process caused by super monomer.[Conclusion] The study provided some helpful references for the forecast of strong convection weather in the Zhongchuan Airport in Lanzhou City.
文摘By their definition, destructive hailstorms cause a great deal of damage to property and have been known to be fatal to humans. At present the long term changes in the frequency of these storms are unknown. Records of destructive hailstorms from many different sources in England and Wales go back for several centuries. Recently discovered records of over 30 destructive hailstorms have allowed a better description of hailstorm history since 1780. The data were grouped into 30, 40, and 50 year non-overlapping time periods in relation to time. Increases in their frequency in the 17th and 18th centuries were probably due to an increase in population and better recording. Since 1900 the frequency has significantly declined so that in the present 50 year time period only 22 have been recorded as compared with an average of 49 in both halves of the 19th century. The decline in frequency may be partly due to the big increase in particulate matter from aviation, which leads to a much higher concentration of ice and cloud condensation nuclei, resulting in fewer destructive hailstorms.
基金supported by the National Natural Science Foundation of China(Grant No.42030607)the Beijing Municipal Science and Technology Commission(Grant No.Z251100004525005)the National Science Foundation/National Center for Atmospheric Research,and NASA(Grant No.80NSSC22M0129)。
文摘The growth trajectory of hailstones within clouds has remained elusive due to the inability to trace them directly,impeding the comprehension of their underlying growth mechanisms.This study investigated hailstone vertical growth trajectories by detecting the stable isotope signatures(2H and 18O compositions)of different shells in 27 hailstones from 9hailstorms,which allowed us to capture the ambient temperature during hailstone growth.The vertical growth trajectories were obtained by comparing the isotopic compositions of water condensate in clouds,derived from the Adiabatic Model,with those measured in hailstones.Although hailstone growth was primarily observed in the–10°C to–30°C temperature layer,the embryo formation height and subsequent growth trajectories significantly varied among hailstones.Embryos formed over a wide range of temperatures(–8.7°C to–33.4°C);four originated at temperatures above–15°C and 16originated at temperatures below–20°C,suggesting ice nuclei composed of bioproteins and mineral dust,respectively.Among the 27 measured hailstones,3 exhibited minimal vertical movement,16 exhibited a monotonic rise or fall,and the remaining 8 exhibited alternating up-down trajectories;only one experienced“recycling”during up-down drifting.Trajectory analysis revealed that similar-sized hailstones from a single storm tended to form at similar heights,whereas those larger than 25 mm in diameter exhibited at least one period of upward growth.Vertical trajectories derived from isotopic analysis were corroborated by radar hydrometeor observations.
基金Supported by the National Natural Science Foundation of China (Grant Nos. 40325013, 40505001 and 40135010)
文摘By using the cloud-to-ground (CG) lightning location data from the lightning detection network of He- nan Province, surface Doppler radar data and standard orbit data of PR, TMI and LIS on TRMM satellite, the spatial and temporal characteristics of CG lightning flashes in 10 severe hailstorms are analyzed. The results show that the percentage of +CG lightning in these hailstorms is high with an average value of 45.5%. There is a distinct increase in CG flash rate during the rapid development stage of hailstorms. The hailstone falling corresponds to an active positive flash period, and the increase of +CG flash rate is generally accompanied with a decrease of –CG flash rate. The flash rate declines rapidly during the dissipating stage of hailstorms. The precipitation structure and lightning activity in two typical hail- storms are studied in detail. It is found that strong convective cells with reflectivity greater than 30dBZ mainly are situated in the front region of hailstorms, whereas the trailing stratiform region is in the rear part of the hailstorms. The maximum heights of echo top are higher than 14 km. Convective rain con- tributes much more rainfall to the total than stratiform rain, and the convective rain takes about 85% and 97% of the total in the two cases, respectively. Total lightning in the hailstorms is very active with the flash rate up to 183 fl/min and 55 fl/min, respectively. The results also indicate that most lightning flashes occurred in the echo region greater than 30 dBZ and its immediate periphery. The probability of lightning occurrence is 20 times higher in the convective region than in the stratiform region. The result suggests that the lightning information is helpful to the identification of convective rain region. The linear relationship between flash rate and ice water content is disclosed primarily.
基金Supported by the National(Key)Basic Research and Development(973)Program of China(2014CB441402)Basic Research Project of the Chinese Academy of Meteorological Sciences(2014R017 and 2013Z006)+1 种基金Key Laboratory Open Project of Disasters Research(2014LASW-B08)Natural Science Research for Jiangsu Provincial Higher Education Colleges(14KJA170005)
文摘Two hailstorms that occurred in Beijing and Tianjin,respectively,are investigated,based mainly on the total lightning data observed by the System d＇Alerte Fondre par Interferometric Radioelecctrique（SAFIR3000）,the cloud-to-ground（CG） lightning data of a CG lightning location system,and the echo data of a Doppler radar.Both hailstorms exhibited two lightning frequency peaks：the first was before the hailfall and the second was after the hailfall,with the second peak greater than the first.The dominant polarity of the CG lightning was positive in the stage around the first frequency peak,but changed to negative in the stage around the second frequency peak.The evolution of radar echoes and the height distribution of lightning radiation sources are explored,revealing that both hailstorms had stronger convection and the main positive charge occurred at mid levels during the stage around the first frequency peak.However,whilst the Beijing hailstorm experienced the enhancement of convection,with the main positive charge at upper levels around the second frequency peak,the Tianjin hailstorm generated its second frequency peak during the period when the convection kept weakening and the main positive charge dropped to mid-lower levels.Through evaluation of the radar parameters,we investigate the mechanisms responsible for the second stage of active lightning discharge.Furthermore,the lightning activity exhibited a close relationship with radar echo parameters and hailfall.Lightning jump signals were found before the hailfall and were associated with the change ratio of the 40-dBZ echo volume above the-15℃ level,which demonstrates the application value of lightning data in severe weather warning.
文摘A shower cloud observed in Jiangxi,a hailstorm observed in Hebei and“75.8”torrential rain in Henan are simulated with our microphysical model in a one-dimensional framework.The model,using the radio- sonde data as input,gets its output which shows agreement in many aspects as compared with observations in each case.The glaciation of small cumulus cloud,low precipitation efficiency of hailstorm and the per- sistence of torrential rain are demonstrated.It is also shown that the Bergeron process has little influence, but the warm-rain process plays an important role in the formation of precipitation in cumulonimbus with a warm cloud base.
基金Supported by the National Natural Science Foundation of China under Grant Nos.40505001 and 40325013,and Meteorological Foundation of Shandong Province (2005sdqxj01).
文摘There were three hailstorms in Shandong Province, caused by a same northeast cold eddy situation on 1 June 2002. Cloud-to-ground （CG） flashes occurring in the weather event were observed by Shandong Lightning Detection Network （SLDN）, which consists of 10 sensors covering all over Shandong Province. The temporal and spatial distributions of CG lightning are investigated for the three hailstorms by using the data from SLDN, Doppler radar and satellite. The results show that different thunderstorms present different lightning features even if under the same synoptic situation. The percentage of positive CG lightning is very high during the period of hail falling. CG flashes mainly occurred in the region with a cloud top brightness temperature lower than -50℃. Negative CG flashes usually clustered in the lower temperature region and tended to occur in the region with maximum temperature gradient, while the positive ones usually spread discretely. Negative CG flashes usually occurred in intense echo regions with reflectivity greater than 50 dBz, while the positive CG flashes often occurred in weak and stable echo regions （10-30 dBz） or cloud anvils, although they can be observed in strong convective regions sometimes. Almost all haft falling took place in the stage with active positive flashes, and the peak positive flash rate is a little prior to the hail events. The thunderstorm could lead to disastrous weather when positive CG lightning activities occur in cluster. Severe thunderstorms sometimes present a low flash rate at its vigorous stage, which is probably caused by the ＂mechanism of chargeregion lift＂ through investigating the reflectivity evolution. Combined with the total lightning （intracloud and CG） data obtained by LIS onboard TRMM, the phenomenon of high ratio of intracloud flash to CG flash in severe hailstorm has been discussed. The competition of the same charge sources between different lightning types can also be helpful for explaining the cause of low CG lightning activities in severe storms.
基金the National Natural Science Foundation of China under Grant No. 40605011the Chinese Ministry of Science and Technology under Grant No. 2001CB309402.
文摘In this paper, a hailstorm occurring on 9 May 1999 in Huanghuai region was studied by using the combined data from the precipitation radar （PR）, microwave image （TMI）, and visible infrared scanner （VIRS） on the Tropical Rainfall Measuring Mission （TRMM） satellite. According to the 3-orbit observations of 5- h duration from the TRMM satellite, the variation characteristics of the precipitation structures as well as cloud top temperature and microwave signals of the precipitating cloud were comprehensively analyzed during the evolution of hailstorm. The results show that the precipitation is obviously converted from early hail cloud with strong convection into the later storm cloud with weak convection. For hail cloud, there exists some strong convective cells, and the heavy solid precipitation is shown at the middle-top levels so that the contribution of rainfall amount above the freezing-layer to the column precipitation amount is rather larger than that within the melting-layer. However, for storm cloud, the convective cells are surrounded by the large area of stratiform precipitation, and the precipitation thickness gradually decreases, and the rainfall above the freezing-layer obviously reduces and the contribution of rainfall amount within the melting-layer rapidly increases. Therefore, the larger ratio of rainfall amount above the freezing layer to column precipitation amount is, the more convective the cloud is; reversely, the larger proportion of rainfall below the melting layer is, the more stable the stratiform cloud is. The different changing trends of microwave signals at different precipitation stages show that it is better to consider the structures and stages of precipitating cloud to choose the optimal microwave channels to retrieve surface rainfall.
基金supported by National Natural Science Foundation of China (Grant Nos. 40875080 and 40875002)Ministry of Science and Technology of China (Grant No. 2006BAC12B01-01)
文摘The Regional Atmospheric Modeling System (RAMS) has been used to investigate the effects of varied giant cloud condensation nuclei (GCCN) concentrations on precipitation characteristics of the spring hailstorms in a semi-arid region. The simulation result shows that this variation has significant effects on the storm microphysical processes as well as on the surface precipitation. The coverage of hail and hail mixing ratio maxima in cloud increases with greater GCCN concentrations. The accumulation zone structure benefits the growth of hail particles. Higher GCCN concentrations lead to more supercooled rain water and cloud water available for freezing. This simulation also shows that increasing GCCN concentrations may produce more rainfall on the surface but less hail precipitation, and the total accumulated precipitation increases while the ice phase precipitation decreases. This effect is stronger in polluted air than in clean air. The surface flow field changes with different GCCN concentrations. The identification index of spring hailstorm is different from that of summer hailstorm with a different aerosol background.
基金Supported by the National Natural Science Foundation of China(41175047)National Key Basic Research and Development Program of China(2013CB430104)+3 种基金Forecaster Special Project of China Meteorological Administration Forecaster(CMAYBY2019-47)Zhejiang Science and Technology Plan Project(2016QN02)Major Project of Zhejiang Provincial Department of Science and Technology(2017C03035)Hangzhou Weather Bureau(ZJZBC-19-9103)。
文摘During a hailstorm event,near-surface meso-γvortices along a convergence line interact with hail cells.Herein we investigate this interaction by using observational data and a high-resolution simulation of a hailstorm that occurred over Taizhou(Zhejiang,China)on 19 March 2014.The 10-m surface wind data from automatic weather stations show that several meso-γvortices or vortex-like disturbances existed over the convergence zone and played a vital role in the evolution of the hailstorm and the location of the hail.The model results agree with the observations and present a closer correlation between the hail and the low-level meso-γvortices than those observed.The model simulation indicates that such low-level meso-γvortices can be used to predict the next 10-min hail fallout zone.The lowlevel meso-γvortices originated over the convergence zone and then fed back into the convergence field and provoked a stronger updraft.Vorticity was initiated primarily by stretching and was extended by tilting.A three-dimensional(3-D)flow analysis shows that the existence of low-level meso-γvortices could help enhance a local updraft.Furthermore,the simulation reveals that the low-level meso-γvortices formed in the bounded weak echo region(WER)at the front of the hail cell,enhancing convergence and strengthening updrafts.Graupel was broadly located between the 0°C isothermal line and the top of the clouds,roughly between the 0 and-20°C isothermal lines.Accordingly,the hailstones grew rapidly.The suitable environment and the positive effect of the meso-γvortices on the updrafts enabled hailstorm formation.
