Classification of Hailstone Trajectories in a Hail Cloud over a Semi-Arid Region in China

The growth trajectory of hailstones in clouds determines the ground intensity and spatial distribution of hailfall.A systematic study of hail trajectories can help improve the current scientific understanding of the mechanisms by which hail forms in semi-arid regions of China and,in doing so,improve the quality of hail forecasts and warnings and help to prevent and mitigate disasters.In this study,the WRFv3.7.1 model was employed to provide the background field to drive the hailstone trajectory model.Cluster analysis was then used to classify hail trajectories to investigate the characteristics of different types of hail trajectories and the microphysical characteristics of hail formation.The differences in hail trajectories might be mainly due to differences in the background flow fields and microphysical fields of hail clouds in different regions.Comparative analysis revealed that as the maximum particle size of ground hailfall increased,the maximum supercooled cloud water content and the maximum updraft velocity for the formation and growth of hailstone increased.The larger the size when the hailstone reaches its maximum height,the larger the ground hailstone formed.Overall,the formation and growth of hailstone are caused by the joint action of the dynamical flow field and cloud microphysical processes.The physical processes of hailstone growth and main growth regions differ for different types of hail trajectories.Therefore,different catalytic schemes should be adopted in artificial hail prevention operations for different hail clouds and trajectories due to differences in hail formation processes and ground hailfall characteristics.

Analysis of Two Hailstorm Processes Accompanied with Weak Precipitation in the North of Shandong

Based on conventional observation data,wind profile radar data and data obtained by a microwave radiometer,the formation mechanisms of two hailstorm processes accompanied with weak precipitation in the north of Shandong Province on June 8 and July 1 in 2014 were analyzed. The results showed that energy accumulated before the occurrence of two hailstorm processes. That is,the height of 0 ℃ and-20 ℃ layer dropped rapidly in the period of hailing,and the height of 0 ℃ layer was around 2. 2 km. Echo clusters producing hail still belonged to meso-γ scale-meso-β scale,and the intensity of reflectivity factor exceeded 50 dBz; echo top was at 12-14 km,and vertically integrated liquid water content was over 30 kg/m^2; in the two processes,water accumulation zones were distributed at 0. 6-2. 0 km. In addition,the water vapor conditions of low-level environmental fields were poor,which resulted in small rainfall in the two processes. However,there were significant differences between the two processes in terms of influencing systems,motion path of hail,changes of ground meteorological elements and disasters. The influencing systems of the " 608" process were the cold vortex,transverse trough and cold front. Convective clouds moved from the northwest to the southeast,and ground temperature dropped,while dew point and ground pressure rose; wind direction changed suddenly with the movement of cold front,and there was no disaster. The influencing systems of the " 701" process were the upper trough,shear line and convergence line. Convective clouds moved from the south to the north. When convective clouds moved to the station,ground temperature dropped,and there was no obvious change in dew point; ground pressure declined sharply,and wind speed was small,but wind direction was changeable,so that the local direct economic loss was up to about 0. 2 billion yuan.

Satellite Retrieval of a Strong Hailstorm Process

A case of hailstorm process occurring on 24 June 2006 in northwestern China was studied using satellite retrieval methodology. The particle effective radius (re) in the cloud tops was calculated by the reflectance in the 3.7 μm channel, and cloud-top microphysical properties were vividly represented using the RGB visual multispectral classification scheme. The microphysical zones of clouds and the processes of hail formation and develop-ment are inferred using the relations of cloud-top temperature (T) versus re for the tops of convective clouds. The results show that particle effective radius was smaller near the cloud base of hailstorm. There was a deep zone of diffusional droplet growth at the low level where the particles grew slowly with height, and there existed an evident area of small ice particles in the cloud top, suggesting the existence of a strong updraft in the clouds. The low glaciated temperature indicated a great depth from the cloud base to the glaciation height, which provided a deep layer of supercooled water for hail growth.

Synoptic-Thermodynamic Analysis of Pervasive Hailstorm Case Study: Tehran, March 30, 2015

The objective here is to assess the atmospheric evaluations with respect to the perilous hailstorm phenomenon in Tehran. To accomplish this study, the available data regarding 9 (WW) present weather codes that reveal the hailstorm phenomenon with different intensities in 3 hrs observations for 6 meteorological stations of Tehran and vicinity for the period between 1985-2015 are applied. It is revealed that hail occurrence in Tehran is at its maximum in transition seasons of spring and fall between the hrs. 6 - 18 (UTC). It is found that the instability indexes intensify in the afternoon with a higher atmospheric flotation indicative of the possibility in occurrence of thunder hailstorm. Synoptic assessments point to the fact that the synoptic pattern created this thunder storm due to expansion of two: low-pressure cores over Arabia and North-Europe and the cold high-pressure over South Russia with a NS orientation have developed an intense pressure gradient over Tehran province. The study area being located at the left exit of sub-tropical jet stream has made a Baroclinic atmosphere condition on Tehran province. Access to great humidity resources of Mediterranean and Black seas and a drastic decrease of temperature at the upper level of the cloud verifies the hail occurrence on March 30th of 2015 in Tehran.

Evolution Characteristics of a Local Strong Hailstorm in Shandong Peninsula

On May 28,2018,a strong hailstorm accompanying gale(with speed of 17 m/s)and hail(with the maximum diameter of 42 mm)occurred in Yantai in Shandong Peninsula.Based on the conventional weather observation,Doppler weather radar,and automatic weather station data,the evolution characteristics of the strong hailstorm in Shandong Peninsula were analyzed.The results show that this multi-cell strong storm occurred under the background of high-altitude cold vortex.The strong cold advection at the middle and high altitudes and the weak warm advection at the low altitude formed a strong unstable stratification,and also led to cooling at the middle altitudes at the same time.The height of 0 and-20℃dropped significantly,which provided better environmental conditions for the growth of hail in the air.The lower temperature 0℃also ensured less melting of hail during falling,and the middle dry layer was conducive to the formation of thunderstorm gale.The vertical wind shear above medium intensity was the development and maintenance mechanism of thunderstorm cells gradually evolving into a strong hailstorm.From the analysis of radar echo characteristics,it is found that it was a strong hailstorm weather process caused by the linear multi-cell storm.The thunderstorm cells that could produce large hail occurred and developed,and the whole process lasted for 2 h under the triggering of the convergence line formed by the interaction of the sea breeze front and ground cold front.It had obvious characteristics of hail such as three-body scattering spikes,side-lobe echoes,high-hanging strong echoes,as well as the characteristics of thunderstorm gale such as arcuate echoes,middle-level radial convergence,and back side inflow.The storm development process was accompanied by backward propagation,but the long axis of the line storm was basically perpendicular to the movement direction of the storm,so there was no short-term heavy precipitation.The stratification instability conditions,water vapor conditions and ground convergence conditions in the eastern part of the peninsula were significantly worse than those in the western part.As a result,the thunderstorm cells first appeared in Laizhou,and then developed into the linear multi-cell storm in the process of eastward movement.Finally,it was rapidly weakened and disappeared after passing through Yantai.

Analysis on Echo Characteristics of Weather Radar of One Hailstorm Process in the First Division

Based on weather radar observation data,development and evolution characteristics of radar intensity echoes PPI and RHI of one ha shooting weather process in the Fifth Regiment of the First Division on May 24,2011 were analyzed. The results showed that local thermal forcin effect was obvious. The Fifth Regiment is close to mountain region,and the supplement of downward cold air from the mountain region was th most direct,and the supplement efficiency was the highest,which was main cause for the hail shooting generated by local severe convective weath er in west area of south Xinjiang. In the hail weather development process,vault( weak echo zone),front suspending echo and echo wall of supe cell on radar echo showed that airflow activity was strong in windstorm,which had an important indication significance for discrimination of ha cloud. The research could provide reference basis for conducting artificial hail suppression and proximity prediction of severe convective weather i reclamation area in the future,and had certain indication significance and better application value.

Multi-scale Analysis of a Hailstorm and Short-time Heavy Rainfall Process in Hohhot City

Based on the conventional observation data,satellite,radar,automatic observation and other refined monitoring data,the severe hail weather in Hohhot City on July 29,2015 was analyzed at multiple scales.The results showed that from the perspective of synoptic-scale system,high-altitude cold air invaded Mongol shortwave trough,and the North China small high pressure and the subtropical high formed a warm shear line;the surface convergence line triggered severe convection weather.Unstable vertical structure,continuous increase of low-level humidity,more drier of high altitudes and the wind direction shear at 180° triggered hailstorm and lightning weather in Hohhot.α-scale convective cloud clusters were maintained in Hohhot,and the ground "herringbone" shear line oscillated violently between the north and the south.Strong lightning and big hails appeared on the ground.The "herringbone" shear line lifted slowly to the north,and there was short-time heavy precipitation on the ground.Radar products showed "bow echo",and the echo had a hanging structure;a mesoscale cyclone was formed 3 km away from the ground.On the radar wind profile,it can be seen that low-layer warm advection and strong wind shear triggered strong hailstorm in Hohhot.The disappearance of low- level warm advection and the maintenance of strong vertical shear of wind produced short-time heavy precipitation.There was a small difference between short-time heavy precipitation and hail in echo top height,but the coverage was significantly reduced.In Hohhot City,vertically integrated liquid water content quickly increased during the hail,and decreased during the short-time heavy precipitation.

Multi-Source Data Analyses of Processes of a Squall Line and the Gale Weather with Heavy Hails before the Squall Line

Through multi-source data analyses of regional automatic station data, wind profiling radar, lightning information, new-generation weather-radar echo data and conventional observations in Fujian Province, and others, this paper finds out aspects to focus on for potential forecasts and the nowcasting of wide-range gale weathers with thunderstorms and hail weathers in west Fujian Province on April 26th, 2016. Thus providing a basis for future forecasting of such catastrophic meteorological activities. Results of analyses showed that being affected by the eastward moving of upper troughs and the eastward and southward moving of low-level vortex shears, cold air and warm air strongly intersected in west Fujian Province;noticeable cold and warm advection formed the temperature frontal-zone;and under the triggering of the ground convergence line, impetuses formed by the strong convergent uplift before the south troughs forcibly produced wide-range squall lines, hails and other strong convective weathers. The squall line was caused by baroclinic frontogenesis. Hails with a diameter of up to 3 cm happened in the prefrontal warm zone. Supercells were generated and developed in the 80 km hot low-pressure convergence zone before the squall line moved along the direction at about 25° to the right of the mean wind field of the environment, belonged to right-shifting hailstorms, were of characteristics representing the hook echo and were of characteristics that the strength of the echo was high. On the afternoon of 26th, on the ground, temperature and humidity strongly increased. Fujian was located in the warm zone in the south side of the inverted trough. The specific humidity at 850 hPa was higher than 12 g/kg. The positive temperature change lasted for 24 hours. In the inland, the ridge was warm, while the trough was cold. Strong vertical wind shears that reached 20 m/s at 925 - 500 hPa and others were beneficial environmental conditions for forming the process of strong convective weather of baroclinic frontogenesis for this time.

Harm of Hail to Crops and Countermeasures of Artificial Hail Suppression in Ulanqab City

Hail is one of meteorological disasters affecting crop growth in Ulanqab City.It happens frequently from May to September,and this period is also the main growing season of crops.In this period,hail will cause damage to crops,make farmland soil harden,and bring varying degrees of harm to agricultural production.Artificial hail suppression is an important scientific and technological means for disaster prevention and mitigation.It is necessary to strengthen the monitoring,analysis and forecast of severe convection weather,intensify the release of early warning information of hail weather,provide accurate and reliable real-time information for the implementation of artificial hail suppression operations,strengthen the implementation of artificial weather modification,effectively carry out artificial hail suppression operations,and avoid and reduce the impact of hail disaster.

Analysis of a Large-scale Hail Process in Ulanqab City

Based on the weather monitoring data,NCEP/NCAR reanalysis data and Doppler weather radar data,the circulation background,atmospheric stability and changing characteristics of radar echoes of a large-scale hail weather process in Ulanqab City on July 5,2021 were analyzed.The results show that this hail weather process occurred in the summer afternoon of the hail-prone period in Ulanqab City,and was formed under the influence of upper trough and the circulation background of"two troughs and one ridge",which was conducive to the occurrence of strong convection weather.The low-level shear line provided the dynamic and water vapor conditions for the occurrence of the hail.In strong convection weather,water vapor was transported mainly from the Bay of Bengal,India and Nepal over the Himalayas.Before the occurrence of strong convection weather,water vapor transport increased significantly,and the low-level water vapor concentrated below 400 hPa,with obvious convergence and vertical transport.The characteristic parameters of radar echoes,such as combined reflectivity,vertically integrated liquid,and echo top height,increased significantly before and during the occurrence of hail,which had good indicative significance for the prediction and early warning of hail.

Numerical Simulations of the Physical Process for Hailstone Growth

Theoretical and experimental studies show that during hail growth the heatand mass transfers play a determinant role in growth rates and different structures. However, manynumerical model researchers made extrapolation of the key heat transfer coefficient of the thermalbalance expression from measurements of evaporating water droplets obtained under small Renoldsnumbers (Re ≤ 200) introduced by Ranz and Marshall, leading to great difference from reality. Thispaper is devoted to the parameterization of measured heat transfer coefficients under Renoldsnumbers related to actual hail scales proposed by Zheng, which are then applied, to Hu-He 1D and 3Dmodels for hail growth respectively, indicating that the melting rate of a hailstone is 12%-50%bigger, the evaporation rate is 10%-200% higher and the dry-wet growth rate is 10%-40% larger fromthe present simulations than from the prototype models.

Damage in hybrid corrugated core sandwich structures under high velocity hail ice impact:A numerical study

Potential damage in composite structures caused by hail ice impact is an essential safety threat to the aircraft in flight.In this study,a nonlinear finite element(FE)model is developed to investigate the dynamic response and damage behavior of hybrid corrugated sandwich structures subjected to high velocity hail ice impact.The impact and breaking behavior of hail are described using the FE-smoothed particle hydrodynamics(FE-SPH)method.A rate-dependent progressive damage model is employed to capture the intra-laminar damage response;cohesive element and surface-based cohesive contact are implemented to predict the inter-laminar delamination and sheet/core debonding phenomena respectively.The transient processes of sandwich structure under different hail ice impact conditions are analyzed.Comparative analysis is conducted to address the influences of core shape and impact position on the impact performance of sandwich structures and the corresponding energy absorption characteristics are also revealed.

Analysis of a Rare Large-scale Hail Process in Yantai and Weihai

A rare large-scale hail process in Yantai and Weihai City in the autumn of 2021 was analyzed based on the surface meteorology,high-altitude observation and S-band radar detection data.The results showed that this process was influenced by shallow trough,and strong upper-level jet stream in the middle and upper levels guided the intrusion of mid-level cold air into the warm and humid environment at the lower level.The shear lines and trunk lines in the lower level also provided certain triggering conditions for uplift,brewing conditions suitable for the occurrence and development of strong convection.The vertical wind shear was unusually large,and vertical wind shear was up to 10 m/s at 0-1 km,20 m/s at 0-3 km,and 32 m/s at 0-6 km,which was conducive to the growth of the storm.In this process,isolated multi-cell thunderstorm was generated at the beginning,and then it developed and strengthened continuously,moving to the southeast.In the later stage,a convection cell was born at the boundary between Yantai and Weihai,and developed into supercell storm.The storm lasted for a long time,and continued to develop and strengthen as it moved eastward,affecting most areas of Weihai from northwest to southeast.In the development stage of the storm,the radar reflectivity factor had obvious characteristics of hook echo and three-body scatter spike,and there was echo overhang and other hail echo features in the middle layer.Weak mesocyclone appeared at a low elevation,and there was the potential for the occurrence of tornado.

Analysis of Characteristics of Hail Disaster and a Typical Hail Suppression Process in Qujing City

Based on the data of hail disaster in Qujing City and the detection data of the new generation of Doppler weather radar, the spatial and temporal distribution characteristics of hail disaster and hail suppression operations in Qujing City were analyzed statistically, and the hail suppression operations of a typical cell case was analyzed. The results showed that the number of hail days and hail frequency showed an increasing trend in Qujing City from 2017 to 2022, and the number of artificial hail suppression operations increased accordingly. Hail disaster occurred most frequently in Xuanwei City. Through the analysis of hail suppression operations of a typical cell case, it is found that the operations were timely, and the location was reasonable. The ammunition used was sufficient, and the overall effect of the hail suppression operations was good.

Risk Assessment of Hail Disaster on Cotton——A Case Study in Anhui Province

[Objective] The aim was to reveal the pattern of hail disaster risk for cotton in Anhui Province. [Method] Based on database of risk evaluation on hail disaster for cotton in Anhui Province, statistical inference and comprehensive indices measurement were made use of for extraction of disastrous index of hail （H） and loss rate of cotton （L）. Hail vulnerability curves in four stages （seedling, bud, boll and boll opening stages） of cotton were fitted by Matlab and SPSS software. Risk evaluation on hail disaster of cotton in Anhui Province was conducted and the related map was drawn on basis of yearly model of loss rate （by hail disaster）, as follows： Sa=n∑i=1Si-a∏i=1Si=1-（1-Si） [Result] In Anhui Province, high risk area by hail concentrates in northeast regions and mountainous regions in west of Anhui, and lower risk area is distributed in middle and down streams of Yangtze River and mountainous area in south of Anhui. [Conclusion] The research explored evaluation methods on hail risks based on the limited information, and could provide references for risk evaluation on hail disaster in other regions.

Analysis of Supercell Storm Structure and Mesocyclone Parameters

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.

Analysis of Physical Quantities and Radar Parameters about Hail Shooting and Heavy Convective Rainfall

[Objective] The paper is to analyze physical quantities and radar parameter of hail shooting and heavy convective rainfall weather. [Method] Using radar data of Jinan station during 2002 and 2008, combined with sounding data, the physical quantities and radar parameter of hail shooting and heavy convective rainfall weather are compared and analyzed. [Result] The smaller Sl is conducive to the generation of hail weather. When K〉 35 ~C, the probability for occurrence of heavy rainfall weather is significantly increased; when K〈20 ^（3, the probability for occurrence of heavy rainfall weather is significantly decreased. When CAPE value is greater than 1 500 J/KG, the probability for occurrence of hail weather is significantly decreased, while the probability for occurrence of heavy rainfall weather is significantly in- creased. The possibility for occurrence of hail monomer is small when the wind shear is less than 5 m/s; and it is large while wind shear is greater than 20 m/s. The radar forecasting indexes of hail monomer is as follows： VIL value reaches 35 kg/m2 （May）, 43 kg/m2 （June and July）, the monomer height is greater than 9 km, the maximum reflectivity factor is larger than 60 dBz, strong center height reaches 3.3 km （May）, 4.3 km （June） and 5.5 km （July）; VlL value of heavy rainfall monomer generally is below 25 kg/m2. [Conclusion] The paper provides basis form prediction of hail and heavy rainfall.

Hail Sensing Probes: Feasibility Analysis for Probes to Monitor and Study Hail

This work presents the feasibility study regarding the realization of hail sensing probes for remote sensing and study of hail. The probes are designed as artificial hailstones in order to study both the physical properties of the portion of atmosphere where the formation of hail occurs and the modification of atmospheric conditions while the hailstones are falling to the ground. The basic idea is to realize sensors with a similar fluid-dynamic behavior with respect to hailstones;the density, the weight and the size of the probes are determined. Consequently, the specification of the electronic boards, sensors, and material to realize the probes are studied and presented. The hail sensing probes can be dropped by a plane, or potentially a UAV (Unmanned Aircraft Vehicle), which fly above and through the clouds where the hail formation occurs. During their falling to the ground, the sensors installed on the probe measure directly different parameters such as humidity, temperature, pressure, acceleration. All data are sent to a receiver located on the ground. The study of the sampling frequency of each sensor is presented, together with the analysis of the propagation channel, in order to assure a robust communication link between probes and the ground receiver. The energy balance is also computed. The work demonstrates that a set of this kind of disposable sensors can be realized. They can be used for efficient monitoring operations and studies of hail formation dynamics and conditions, thus increasing the set of instruments for the monitoring and remote sensing of hail.

Diagnostic Analysis on A Hail Storm Occurred in Dalian Area

By using regular meteorological data and Doppler radar data,causes for a hail storm over northern area of Dalian on Oct.13,2009 were analyzed from several aspects,including synoptic background,T-LnP charts and the characteristics of radar reflectivity factor evolution.The results showed that the hail storm occurred in downstream of 500 hPa trough.The 500 hPa cold trough turned zonally and triggered the formation of shear line on lower level.Before the hail event,instability energy and moisture supply were observed.The shear line on lower level intensified the atmospheric instability,promoted the release of potential energy,caused the hail event.The cooperation of upper and lower level jet streams provided favorable dynamic condition for strong convection development.The Doppler radar analysis showed that strong convection was comprised of multiple convection cells,which demonstrated 'L' and 'V' shapes during mature stage,with peak intensity of 50-60 dBz.

Distribution Characteristics of Heavy Metals and Grain Size of Sediments from Hailing Bay, China

The geochemical properties of sediment in the nearby seawater areas of Hailing Bay of the western Guangdong province were first time investigated in the dry period of 2001 and the flood period of 2002, respectively. The temporal and spatial characteristics of Cu, Pb, Zn, Cd and Hg concentrations, organic carbon and total sulfides contents, and granulometric distribution in the surface sediment from the Hailing Bay were analyzed. Results demonstrated that there were no remarkable changes in the composition of sediment between the dry period and the flood period; the average concentrations of Cu, Pb, Zn, Cd and Hg were 32.1 ± 17.5, 36.1 ± 10.0, 107.0 ± 37.4, 0.26± 0.15 and 0.109 ± 0.073 mg·kg-1, respectively; the organic carbon and total sulfides contents were 1.33 ± 0.53 % and 140.13 ± 136.42 mg·kg-1, respectively; surface sediments were dominated by clayey silt and sand, and their mean grain size was 4.62 ± 2.36 φ and in the range 0.52-7.55 φ; there existed obvious correlation between the concentrations of Cu, Pb, Zn and Hg, and among Cu, Pb, Zn and Hg concentrations, organic carbon contents and grain size of sediments.