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.

Will Online Car-Hailing Affect Consumers’ Decisions about Automobile Purchase?—An Empirical Study Based on Questionnaire Investigation

The online car-hailing industry, which provides the right of use, has a certain impact on the traditional automobile market, but there is no unified theory on whether it has a positive impact or a negative impact. Based on 362 consumer questionnaire data, this study builds a structural equation model to discuss the driving factors of residents’ choice of online car-hailing and whether the development of online car-hailing will have a certain substitution impact on the sales of private cars. From the perspective of consumers’ purchase intention, the research results show that consumers’ price consciousness, convenience consciousness, environmental protection consciousness and possession tendency will affect their choice of travel mode, and the use of online car-hailing is positively correlated with consumers’ willingness to replace private car ownership with online car-hailing.

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.

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.

网约车平台算法个性化定价、乘客履约率及其监管对策

网约车平台算法个性化定价产生了复杂的市场影响,相比传统出租车服务,网约车乘客违约率达30%左右,因此算法个性化定价对乘客违约率的影响机制以及乘客是否履约的关键特征值得探索。文中尝试运用矩形Hotelling模型建立算法个性化定价与乘客违约率的因果关联机制,以两个网约车平台之间的Stackelberg博弈模型揭示歧视性定价、乘客违约率与平台之间竞争强度的关系。进一步运用网约车平台订单大数据,以Bhattacharyya距离、提升决策树及改进拉斯维加斯方法(包裹法)等归纳学习工具对网约车平台百万量级订单进行数据挖掘,找出决定乘客是否履约的关键特征。分析结果表明,平台进行个性化定价时乘客的最终消费选择主要取决于价格因素;而改进车辆匹配、派单策略及减少乘客候车时间可显著提高订单履约率。研究结果对网约车平台完善定价及运营策略以维持双边市场用户数量、保证平台持续成功运营具有重要参考价值,也为反垄断部门干预平台个性化定价提供了理论依据。

一次冰雹云发展的雷达回波特征分析及其防雹作业效果物理检验

利用云南昭通CC雷达和威宁探空等资料,对贵州省威宁县2017年7月23日的一次冰雹云发展过程的雷达基本反射率因子和径向速度的变化特征进行分析,同时通过插值得到剖面变化特征,研究雹云垂直结构演变,并根据雷达回波顶高、强回波中心(45 dBZ)高度、组合反射率和垂直累积液态水含量(VIL)这4个雷达探测特征物理量,进行时间序列分析,得到防雹作业效果。结果表明:(1)降雹前对流单体的合并使回波强度和VIL分别跃增至60 dBZ和50 kg·m^(-2)以上,冰雹云的雷达回波出现旁瓣回波和“V”形缺口。(2)中低层气流的径向辐合及高层强辐散带来的强烈抽吸作用所产生的上升气流,使雹云能够稳定维持和发展。(3)防雹作业后,雹云开始由上至下分裂直至完全分裂成两个孤立弱单体,回波顶高明显降低,组合反射率较峰值下降近30 dBZ。(4)在作业单元和对比单元的生命史时间内,作业单元的4个雷达探测特征物理量下降速率均大于对比单元的,表明防雹作业有效抑制了雹云的发展。通过对比分析发现,防雹作业24 min后,4个雷达探测特征物理量的双比值均小于1,进一步证明防雹作业取得了明显的正效果,加速了对流单体的消亡。

一次强冰雹超级单体风暴双偏振参量特征分析

利用济南S波段双偏振多普勒天气雷达资料、章丘探空和地面常规气象观测资料及灾情调查,对2021年7月9日发生在济南章丘的一次特大冰雹超级单体风暴双偏振和微物理结构特征进行了分析。结果表明:冷涡天气背景下,强的垂直风切变和强的对流有效位能,利于超级单体的形成与维持。阵风锋是风暴触发机制,也是风暴长时间维持机制。初始风暴由阵风锋触发,经过合并发展产生超级单体。成熟阶段,风暴西侧与阵风锋交汇区域不断激发新生单体,并与主体合并,风暴长时间维持。风暴顶强辐散是中气旋长时间维持和风暴顶高度较高的关键因子之一。特大冰雹阶段风暴底层右后有明显的入流缺口,其前侧有差分反射率(Z_(DR))弧,表现为少量大的液态粒子或小的湿冰粒子,入流缺口左侧强反射率因子区对应小的Z_(DR)和小的相关系数,为冰雹降落区。垂直结构上,强上升气流区一侧存在深厚的有界弱回波区,0℃层高度之下分布有Z_(DR)环,有界弱回波区内及上方存在Z_(DR)柱,且高度较高,含有少许偏大的液态或融化的小的冰相粒子。较高的Z_(DR)柱表明风暴内上升气流强盛且高度较高,利于风暴的发展与维持以及冰雹粒子的湿增长。

隐私保护的网约出行的研究综述

为高效利用交通资源,在线网约出行(ORH)服务整合车辆供给和乘客请求信息,派遣符合条件的车辆提供非巡游的出行服务。人们在享受ORH服务带来的便利时,也面临着严重的隐私泄露风险。为此,许多研究利用密码学技术设计隐私保护的ORH服务。首先,本文介绍了隐私保护的ORH服务主要面临的城市动态场景下高效计算密态行程开销、实时动态规划密态行程、安全共享不同ORH服务的运力资源等挑战。然后,回顾了欧式距离、路网距离和行驶时间三类行程开销的安全计算方法,其中,欧式距离计算效率高,但误差大,现有路网距离和行驶时长的安全计算方法多数面向静态路网场景,针对城市动态路网场景的安全计算方法有待进一步研究。分析了面向司机、乘客、ORH平台的行程规划问题的求解方法,现有研究往往仅针对司机、乘客或ORH平台的单一目标进行行程规划,事实上行程规划不但要考虑ORH平台自身收益,更要同时兼顾乘客和司机的用户体验。综述了隐私感知的行程预处理方法,单车单客模式、单车多客模式的行程安全共享方法,并总结了其不足与启示。多车单客、多车多客动态模式的行程安全共享有待进一步研究。最后,从城市动态路网下高效的密态行程开销的安全计算与比较、多方隐私保护的大规模密态行程动态规划与安全保障、跨服务域的去中心化密态行程协作共享、ORH服务的法律法规合规保证四方面展望了隐私保护的ORH服务的未来研究方向。本文旨在保护多方隐私的前提下,提高ORH服务质量、促进多ORH服务合作,使得网约出行更加智慧、更加安全。

天气雷达三体散射长钉回波特征分析

利用2016—2020年中国中东部地区47个强对流个例中50部S波段多普勒天气雷达的基本反射率因子产品资料,在筛选出2626个样本的基础上,分析三体散射长钉(TBSS)特征。结果表明:TBSS在1.5 km和5 km高度附近出现频次最高;在2.4°仰角出现频次最高。TBSS主要出现在雷达静锥区边缘至雷达径向距离210 km范围,在距离雷达115 km附近达到峰值;TBSS在雷达极坐标系中呈现南多北少、西多东少的形势;当对流风暴移动方向与雷达径向方向的夹角大于30°时有利于观测到TBSS。TBSS回波强度在起始端径向向外0~15 km范围内迅速降低至5 dBz,15 km之后在-5~10 dBz波动,TBSS区域中70%以上为低于25 dBz的弱回波;99%的TBSS长度小于40 km,不同长度的TBSS形态符合正态分布。TBSS出现频次和长度与强回波的中心最高值和区域面积没有显著相关关系。

贵州威宁对流单体雷达回波分层结构特征分析

本文选取了2017—2020年威宁县111个对流单体(35个冰雹云单体和76个雷雨云单体),着重分析了对流单体雷达回波在垂直指向上的分层结构特征,并结合双偏振雷达观测分析了对流云单体偏振参量和水凝物相态分布特征。研究分析结果表明:①威宁对流单体雷达回波典型特征量基本一致,对流单体生命史周期约为100 min,最大反射率因子主要位于与0℃层高度差±2.0 km的范围内;②当对流单体雷达回波强度从45 dBz发展到55 dBz以上时,冰雹云具有发展迅速且持续时间长的特点,冰雹大小则与强回波在融化层高度以上的扩展高度存在一定的对应关系,高度越高、冰雹越大;③X波段双偏振天气雷达能够较好地反映降水粒子类型,基本符合粒子形状、大小和相态分布的特点,但应考虑降水相态粒子处于临界过渡区域的转化特点;④威宁多小冰雹主要与垂直风切变较弱、对流有效位能CAPE值不稳定能量偏低,且中小冰雹在下落过程中逐渐融化变小有关。

网约车实时订单在线选择策略设计与竞争分析

针对现实中网约车司机追求自身利益最大化而产生的频繁“拒单”现象,为优化乘客满意度、网约车平台调度效率和司机个人收益,提出派单模式下网约车司机实时订单决策问题,并采用在线策略设计与竞争分析展开研究。本文讨论了订单行驶距离小于返空距离的情形,即订单不收取车辆返空费。研究了一般网络上网约车实时在线调度的竞争比下界,并设计了最优调度策略——阈值策略(PT策略),分析了策略的竞争性能。最后,通过算例分析证明,PT策略能有效帮助网约车司机提高工作期间实时订单的总收益,从而降低司机“拒单”行为,在实际生活中具有很强的实用性,对网约车司机、网约车平台和政府具有一定管理启示。

基于结构方程的网约车平台用户价值共创行为影响因素研究

随着各种数字技术的迅速发展,我们已经进入数字经济时代。人们生活也因此发生了巨大变化,其中对人们影响较大的便是出行方式的改变。移动互联网技术的发展带来了网约车平台的诞生,也改变了顾客在企业价值创造过程中的地位。用户价值共创行为对于网约车平台和用户自身是一个双赢的过程,然而在现实中却只有少数用户有意愿参与价值共创活动,所以了解网约车平台用户价值共创行为的关键影响因素具有重要的实践价值。因此,文章选取绩效期望、努力期望、社会影响、服务体验和价值共创意愿五个变量,通过构建结构方程模型探究了网约车平台用户价值共创行为的影响因素。研究发现,社会影响和服务体验正向影响价值共创意愿,价值共创意愿进一步正向影响价值共创行为。

播撒碘化银人工消雹对冰雹云微物理过程和起放电过程影响的数值模拟研究

为了全面了解人工消雹对云中冰相粒子的浓度和时空变化以及冰雹云微物理过程和起放电的影响,本文利用包含了AgI催化方案的三维强风暴动力电耦合数值模式,以AgI播撒量为唯一变化量进行了多组模拟实验。结果表明,催化过后,整体上,-40~0℃范围内的冰晶、雪花和霰粒子数浓度和比含水量增多。播撒AgI使霰的平均尺度减小,向雹的转化比例大为降低,因此冰雹的比含水量和浓度都减小。随着AgI播撒剂量的增加,冰晶、雪花和霰粒子的数浓度和比含量整体变化趋势不变,增大与减小区域相对应,但变化更明显;消雹效果会更好,但降雨量呈先增加后减小。播撒AgI会使冰雹云前期正的非感应起电率区出现时间提前,中心增强,上界高度抬升,后期负的非感应起电率区中心增强。所以,播撒后前期主要使底部次正电荷区增强,后期主要使上方主正电荷区和中部负电荷区增强。随着催化剂量增多,这些变化越明显。播撒AgI对地闪有一定的抑制作用,而使云闪和总闪少量增多,首次放电和云闪的峰值时间提前,放电持续性更强,闪电频发时段的闪电频率略有降低。

云南春季典型冰雹天气的云微物理特征

冰雹形成的天气和云微物理机制是人工防雹的基础。采用观测和数值模拟相结合的方法,研究2023年3月28日云南南部红河州典型冰雹过程的天气和微物理特征。结果表明:此次天气过程与青藏高原南支西风槽波动和南亚副热带高压外围西南暖湿气流输送的协同作用密切相关;地面降雹以小于10 mm的小冰雹粒子为主,最大冰雹尺度达到20 mm;冰雹云微物理结构显示为暖底云,暖雨过程活跃;双偏振雷达差分反射率、差分相移率和相关系数显示,冰雹初始形成区存在接近球形的冰雹和过冷雨滴,说明冰雹胚胎的形成与过冷雨滴冻结有关;冰雹在下落过程中雷达回波增强,偏振雷达参数显示冰雹的水平取向显著增加,形状由球状向盘状转变,冰雹在下落过程得到进一步增长,形状也发生变化。这些观测宏微观特征与数值模拟的冰雹形成机制有较好的一致性。

基于Logistic回归模型的风云二号(G星)降雹识别技术研究

以风云二号(G星)的7项卫星反演产品(云顶温度、云顶高度、液水路径、过冷层厚度、光学厚度、有效粒子半径以及黑体亮温)作为模型的输入参数建立Logistic回归冰雹识别模型,开展贵州降雹识别技术研究。收集了2020年3—5月期间11个降雹日共计136组风云二号(G星)卫星反演产品数据,其中包括了68个降雹点以及68个未降雹点数据,将每个降雹点降雹时刻前后15 min内的反演产品作为该点的数据。同时选取相应的未降雹点作为对比。将所建立的冰雹数据集分为训练集与检验集。其中,训练集为随机选取的116组数据,用于训练模型(分别包括58组降雹点与未降雹点数据),模型检验集为剩余20组数据(分别包括10组降雹点与未降雹点数据)。利用训练集完成Logistic回归冰雹识别模型建立,利用检验集验证模型识别效果。结果表明,Logistic回归冰雹识别模型对降雹的识别准确率为85%,其中对检验集中的10个降雹点识别准确率为90%,漏报率为10%;对10个未降雹点识别准确率为80%,空报率为20%。

陕西商洛“6·30”强冰雹过程环境条件及雷达特征分析

利用地面加密资料、多普勒雷达观测资料、ERA5(0.25°×0.25°)逐小时再分析资料,对2022年6月30日陕南东部一次极端强冰雹天气过程的环境条件及雷达特征进行分析。结果表明:高空冷涡后部偏北气流带动高层干冷空气南下,叠加在低层西南暖湿气流之上,造成强的位势不稳定层结,为强对流天气发生提供了有利的背景条件。较强的低层水汽输送及辐合、强的对流有效位能、适宜的0℃和-20℃等温线高度、0-6 km中等强度的垂直风切变为冰雹天气发生提供了有利的环境条件,中高层冷空气及地面冷池触发了强对流天气。适宜的冷暖云厚度有利于雹粒的增大;强的上升气流有利于小雹粒在丰富的过冷水中循环增长。基本反射率因子图上有三体散射,最强反射率因子达65 dBZ以上,剖面图上有低层弱回波区、中高层回波悬垂,50 dBZ以上的强回波核心位置有超过-20℃等温线高度。基本速度图上有中气旋特征,回波顶高对对流发展和减弱有一定指示意义。垂直液态水含量跃增20 kg·m^(-2)以上对冰雹天气预警有一定的指示意义。

非营利性网约车平台定价策略:静态定价vs.峰值定价

本文以社会福利最大化为目标,分别构建了静态定价和峰值定价两种定价策略下非营利性网约车平台的决策模型,对比分析不同定价策略对平台的最优定价、社会福利、消费者剩余和司机剩余的影响。在此基础上,进一步分析了社会福利最大化与利润最大化下网约车平台采用峰值定价时的差异表现。研究发现:(1)当存在服务需求不确定性时,利润最大化的网约车平台选择峰值定价不劣于静态定价;(2)与利润最大化为目标的网约车平台不同,社会福利最大化的非营利网约车平台除了在需求波动非常大情形下考虑使用峰值定价外,应使用静态定价;(3)利润最大化的网约车平台采用峰值定价可能造成供应短缺,而社会福利最大化的网约车平台使用峰值定价总能使得供需匹配,并带来消费者剩余的增长;(4)当出现低需求的概率适中或平台总是处于高需求时,使用静态定价的社会福利最大化的平台可以比利润最大化的平台更好地匹配供需或者使单个消费者获得更高的效用,从而具有更高的消费者福利。上述结论可为各级政府制定网约车平台服务政策方案提供重要的理论支撑和决策参考。