Synergistic Effect of the Planetary-scale Disturbance, Typhoon and Meso-β-scale Convective Vortex on the Extremely Intense Rainstorm on 20 July 2021 in Zhengzhou

On 20 July 2021,northern Henan Province in China experienced catastrophic flooding as a result of an extremely intense rainstorm,with a record-breaking hourly rainfall of 201.9 mm during 0800–0900 UTC and daily accumulated rainfall in Zhengzhou City exceeding 600 mm(“Zhengzhou 7.20 rainstorm”for short).The multi-scale dynamical and thermodynamical mechanisms for this rainstorm are investigated based on station-observed and ERA-5 reanalysis datasets.The backward trajectory tracking shows that the warm,moist air from the northwestern Pacific was mainly transported toward Henan Province by confluent southeasterlies on the northern side of a strong typhoon In-Fa(2021),with the convergent southerlies associated with a weaker typhoon Cempaka(2021)concurrently transporting moisture northward from South China Sea,supporting the rainstorm.In the upper troposphere,two equatorward-intruding potential vorticity(PV)streamers within the planetary-scale wave train were located over northern Henan Province,forming significant divergent flow aloft to induce stronger ascending motion locally.Moreover,the converged moist air was also blocked by the mountains in western Henan Province and forced to rise so that a deep meso-β-scale convective vortex(MβCV)was induced over the west of Zhengzhou City.The PV budget analyses demonstrate that the MβCV development was attributed to the positive feedback between the rainfall-related diabatic heating and high-PV under the strong upward PV advection during the Zhengzhou 7.20 rainstorm.Importantly,the MβCV was forced by upper-level larger-scale westerlies becoming eastward-sloping,which allowed the mixtures of abundant raindrops and hydrometeors to ascend slantwise and accumulate just over Zhengzhou City,resulting in the record-breaking hourly rainfall locally.

Forecast Error and Predictability for the Warm-sector and the Frontal Rainstorm in South China

In south China, warm-sector rainstorms are significantly different from the traditional frontal rainstorms due to complex mechanism, which brings great challenges to their forecast. In this study, based on ensemble forecasting, the high-resolution mesoscale numerical forecast model WRF was used to investigate the effect of initial errors on a warmsector rainstorm and a frontal rainstorm under the same circulation in south China, respectively. We analyzed the sensitivity of forecast errors to the initial errors and their evolution characteristics for the warm-sector and the frontal rainstorm. Additionally, the difference of the predictability was compared via adjusting the initial values of the GOOD member and the BAD member. Compared with the frontal rainstorm, the warm-sector rainstorm was more sensitive to initial error, which increased faster in the warm-sector. Furthermore, the magnitude of error in the warm-sector rainstorm was obviously larger than that of the frontal rainstorm, while the spatial scale of the error was smaller. Similarly, both types of the rainstorm were limited by practical predictability and inherent predictability, while the nonlinear increase characteristics occurred to be more distinct in the warm-sector rainstorm, resulting in the lower inherent predictability.The comparison between the warm-sector rainstorm and the frontal rainstorm revealed that the forecast field was closer to the real situation derived from more accurate initial errors, but only the increase rate in the frontal rainstorm was restrained evidently.

Pore Characteristic Design Method of High-strength Pervious Concrete Based on the Mechanical Properties and Rainstorm Waterlogging Resistance

High-strength pervious concrete(HSPC) with porosity ranging from 0.08% to 2.011% was prepared. The mechanical properties and rainstorm waterlogging resistance of HSPC were evaluated,and a design method of HSPC pore characteristics(porosity and pore diameter) based on the mechanical properties and rainstorm waterlogging resistance was proposed. The results showed that the reduction of effective cross-sectional area caused by artificial channels was the main factor affecting flexural strength but had limited influence on compressive strength. Compared with the concrete matrix without artificial channels,the compressive strength of HSPC with porosity of 2.011% decreased by 7.4%, while the flexural strength decreased by 48.3%. The permeability coefficient of HSPC can reach 16.35 mm/s even at low porosity(2.011%).HSPC can meet the requirements of no rainstorm waterlogging, even if exposed to 100-year rainstorms. When the mechanical properties and rainstorm waterlogging resistance are compromised, the recommended porosity ranges from 1.1% to 3.5%, and the recommended pore diameter ranges from 0.8 to 2.7 mm.

Analysis of Rainstorm Process over Henan Province of China in July 2021

Based on the data from the China National Meteorological Station and the fifth-generation reanalysis data of the European Center for Medium-Range Weather Forecasts, we investigated and examined the precipitation, circulation, and dynamic conditions of the rainstorm in Henan in July 2021. The results show that: 1) This precipitation is of very heavy rainfall level, beginning on the 19th and lasting until the 21st, with a 3-hour cumulative precipitation of more than 200 mm at Zhengzhou station at 19:00 on the 20th. The major focus of this precipitation is in Zhengzhou, Henan Province, and it also radiates to Jiaozuo, Xinxiang, Kaifeng, Xuchang, Pingdingshan, Luoyang, Luohe, and other places. 2) The Western Pacific Subtropical High (WPSH), typhoons “In-Fa” and “Cempaka”, as well as the less dynamic strengthening of the Eurasian trough ridge structure, all contributed to the short-term maintenance of the favorable large-scale circulation background and water vapor conditions for this rainstorm in Henan. 3) The vertical structure of low-level convergence and high-level dispersion near Zhengzhou, together with the topographic blocking and lifting impact, produced favorable dynamic lifting conditions for this rainstorm.

Effect of Fatigue Loading on the Mechanical Properties and Resistance of High-strength Straight-hole Recycled Pervious Concrete to Rainstorm-based Waterlogging

A novel high-strength straight-hole recycled pervious concrete(HSRPC)for the secondary highway pavement was prepared in this paper.This study aimed to investigate the effect of porosity(0.126%,0.502%,and 1.13%),vehicle loading stress level(0.5 and 0.8)and service life on the resistance to rainstormbased waterlogging of HSRPC under fatigue loading.The mechanical properties of HSRPC in terms of flexural strength and dynamic elastic modulus were studied.The waterlogging resistance of HSRPC was described by surface water depth and drainage time.The microstructure of HSRPC were observed with scanning electron microscopy(SEM).Results showed that although the dynamic elastic modulus and flexural strength of HSRPC decreased with the increasing number of fatigue loading,the flexural strength of HSRPC was still greater than5 MPa after design service life of 20 years.After 2.5×10^(5)times of fatigue loading,the permeability coefficient of HSRPC with a porosity of 0.502%and 1.13%increased by 18.4%and 22.9%,respectively;while the permeability coefficient of HSRPC with 0.126%porosity dropped to 0.35 mm/s.The maximum surface water depth of HSRPC with a porosity of 0.126%,0.502%,and 1.13%were 8,5 and 4 mm,respectively.SEM results showed that fatigue loading expanded the number and width of cracks around the tiny pores in HSRPC.

Analysis on the Cause and Forecast Deviation of an Extreme Rainstorm in Changsha Urban Area

Using NCEP reanalysis data,high-altitude and ground observation data,numerical model data,satellite and radar data,formation cause and forecast deviation of an extreme rainstorm process in Changsha urban area at night on June 9,2020 were analyzed.The results showed that(1)the extreme rainstorm process developed near the surface convergence line,with strong localization,short duration and large hourly rainfall intensity.(2)Under the high temperature and high humidity environment,the low-level cold advection and the hot low-pressure system interacted,and the potential con-vective unstable energy was released,and a strong convective weather was formed.(3)The convergence of water vapor in the lower layer and the strong upward movement provided sufficient water vapor for the rainstorm.The low-centroid thunderstorm was the main reason for the extreme rainstorm.(4)The forecast deviation of the numerical model to the low-level shear line and the mesoscale convergence line was an important reason for the forecast deviation of the heavy rainfall area.

Reflection on China's Disaster Prevention and Mitigation Construction after Rainstorm and Snowstorm

On July 10,2004,Beijing was hit by the rainstorm that has not been seen for many years,which caused water accumulation in many places of the urban area,power supply interruption in many places,and traffic paralysis for nearly 5 h. On July 12,2004,the rainstorm in Shanghai lasted less than 1 h,but it caused 7 deaths,more than 20 injuries,extensive power outages and traffic paralysis. At the end of 2005,the continuous snowfall in Weihai City of Shandong Province for half a month caused direct economic losses of over 200 million yuan,and the continuous heavy snowfall had a serious impact on people’s lives. From July 17 to 23,2021,Henan Province suffered a rare extremely heavy rainstorm in history,with a direct economic loss of 120.6 billion yuan. Faced with such urban meteorological disasters and other types of urban disasters,combined with the current situation of disaster prevention and reduction in China,what will managers,decision-makers,and experts and scholars think about from them.

城市新区极端雨洪汇流淹没特性与致灾机理调查研究——以郑州“7.20”特大暴雨(郑东新区)为例

近年来全球极端暴雨发生的可能性与不确定性提高,增加了城市遭遇特大洪涝灾害的风险。城市雨洪与河道洪水有显著差异,灾后雨洪信息快速采集与调研对认清雨洪特性与致灾机理尤显重要。本文以郑州2021年“7.20”特大暴雨为例,结合郑东新区地理与社会环境特点,采用野外调查测量、口述记录、多源数据分析、数值模拟对比相结合的方法开展了城市雨洪汇流淹没特性及致灾机理的调查研究。针对城市雨洪洪痕特征,拟定调查基本方法与适宜工作程序,根据调查区93处洪痕数据绘制了区域雨洪淹没分布图,分析了城市雨洪峰值水位分布特征及调查区汇流特性,探索了道路雨洪汇流流速及行洪道路阻力参数的确定方法。研究表明,城市雨洪地表主要泄流通道是街区道路,汇流方向受连续阻水、导水建筑与路网布局影响,雨洪淹没深度分布与下垫面条件和雨洪汇流特性有关。致灾机理研究分析表明,极端暴雨汇流远超城市排水管网泄流能力,雨洪选择阻力小的街道快速行洪,街道交汇处壅阻引起局部积水严重,这是极端暴雨致灾的直接诱因;而城市新区水系泄洪排涝关系不协调以及清障不力,导致城区河流行洪不畅,干支流异常高水位的顶托,严重降低了管网排涝功能,则是城市雨洪严重积涝致灾的深层原因。研究成果可为城市雨洪调查标准方法的建立与城市新区防洪排涝体系规划提供技术参考。

Analysis of a Local Rainstorm in Central Inner Mongolia

Based on conventional observation data,satellite cloud image data and new generation Doppler radar data,the local rainstorm weather situation and physical quantities in Ulanqab City from 08:00 to 20:00 on June 24,2019 were analyzed by means of synoptic methods.The results show that the local rainstorm was caused by the forward trough system and the convergence of warm and cold air,and triggered by the low-level jet and the surface convergence line.The splitting and merging of cloud clusters in satellite cloud images and strong radar echoes had a good guiding effect on short-term heavy precipitation.

诱发台风暴雨型滑坡的降雨阈值研究——以泰顺县为例

在我国东南沿海地区,台风暴雨诱发了大量山体滑坡。建立诱发台风暴雨型滑坡的降雨阈值模型,可为该地区的滑坡预警提供参考依据。基于浙江省泰顺县2007—2022年以来发生的滑坡信息和日降雨量数据,进行了诱发滑坡的台风暴雨事件编目,初步揭示了台风暴雨型滑坡的发育规律和触发降雨特征,通过降雨强度(I)、降雨历时(D)的幂律关系构建了滑坡临界降雨阈值模型,并开展了不同台风降雨雨型的阈值模型对比。结果表明:台风暴雨型滑坡大量发生在与台风登陆方向接近的迎风坡,坡表植被多为乔木和竹林;诱发滑坡的台风降雨一般持续2~3 d,且降雨过程集中,降雨雨型以单峰型为主,总降雨量一般在200 mm以上;台风暴雨诱发滑坡的降雨阈值显著高于一般性的降雨,这种差异与台风降雨模式及大尺度气候环境有关;雨型也会显著影响降雨阈值,随着降雨峰值的后移,阈值逐渐降低,表明台风暴雨型滑坡对长时间降雨后出现的强降雨事件更加敏感。通过降雨阈值模型对9次台风降雨事件是否诱发滑坡进行了预测,预测结果与实际情况比较吻合,证明该模型及研究思路对台汛期东南沿海的滑坡监测预警有较强的参考价值。

甘肃陇南两次暴雨天气过程对比分析

2017年8月甘肃陇南出现暴雨天气,礼县、武都气象站24 h降水量突破历史极值,极端性和局地性突出。应用欧洲中期天气预报中心(European Centre for Medium-Range Weather Forecasts,ECMWF)第5代全球大气再分析产品ERA5、雷达资料及地面加密观测资料,对2017年8月6—7日、19—20日发生在甘肃省陇南地区的2次暴雨过程进行对比分析,重点讨论2次过程的环流背景以及强降水时段雷达反射率因子、径向速度、物理量特征。结果表明,2次暴雨过程均发生在西风槽偏北气流与中低层偏南暖湿气流交汇处,但是2次过程的主要影响系统及触发条件不同;雷达回波显示8月6—7日由冷式切变线引起的暴雨系统对流性较强,反射率因子值较高、中心高度较低,降水率较大,持续时间短;19—20日暖区降水的反射率因子值较低、中心高度较高,降水率较小,持续时间较长。

水土保持生态建设下的黄土高原典型流域水沙响应

为探讨黄土高原多沙粗沙区流域水沙关系演变特征及其对水土流失治理的响应,以黄河中游无定河流域为研究对象,综合采用水沙关系曲线、数理统计等多种方法,系统分析1956—2019年间无定河流域水沙关系多时间尺度演变特征及其与水土流失治理的协同响应。研究结果表明:1)研究时段内,无定河流域年径流及年输沙量呈锐减趋势(P<0.05),且均在1970年左右发生减少突变;2)流域水沙关系在年际和场次洪水尺度上均发生深刻变化。2010年以后,暴雨频发导致流域内侵蚀物源头供应明显增加,流域河道泥沙输送能力小幅提高;3)水土保持措施实施对流域水沙锐减影响较大。2000年前后在相似降雨条件下,单位降雨量径流量和单位降雨量输沙量较20世纪70年代减少47%和62%。水土保持措施面积增加与流域径流输沙减少呈现较好的一致性,流域水土流失治理在提高黄河多沙粗沙区流域下垫面抗侵蚀能力等方面发挥重要作用。研究结果可为科学认知区域水土流失治理成效及入黄泥沙锐减成因提供参考。

江淮梅雨期持续性暴雨和极端强降水事件的位涡比较分析

基于我国气象台站观测降水数据和欧洲中期天气预报中心(ECMWF)第五代大气再分析资料(ERA5),从位势涡度(位涡)强迫垂直运动的角度,揭示了江淮梅雨期持续性暴雨和极端强降水事件的动力学机制及差异。基于改进的两种事件定义方法,识别出1979—2020年梅雨区共发生了24次持续性暴雨事件及24次极端强降水事件。事件合成分析表明,持续性暴雨事件最强雨带主要位于长江及其以南地区,而极端强降水事件最强雨带则位于长江及其以北地区。持续性暴雨事件与热带大气低频振荡密切相关,其中南亚高压偏东、西北太平洋副热带高压偏西,因而高空偏南的西风急流附近具有高值位涡的干冷空气向南和向低空入侵,在中低层与西南暖湿气流辐合并形成梅雨锋区。极端强降水事件更大程度地取决于偏北的西风急流南侧的高空辐散及位涡强迫的强冷空气。对于极端强降水事件位涡收支的定量诊断表明,在强降水达到峰值及之前,高层负的位涡倾向主要由负的垂直位涡平流所导致,而中低层正的位涡倾向则主要取决于垂直非绝热加热的位涡制造和垂直位涡平流。结合典型个例的垂直速度分解,进一步证实梅雨区上空水平位涡平流随高度增加的垂直分布激发的上升运动分量在极端强降水事件起着重要作用。

沿江城市降雨特性及雨洪关系分析——以四川泸州市为例

沿江城市气候多变,外洪和内涝之间关系复杂,相互影响、相互制约,洪涝统筹是沿江城市面临的最主要问题。分析掌握沿江城市的暴雨、洪水特征,可提前预测不同降雨条件下河道洪水的特性及其对城区排涝的影响,对于城市防洪系统和排涝系统统筹兼顾、合理规划、洪涝预报预警,都具有重要意义。以四川泸州市为例,对暴雨时空分布特征、洪水特征规律等进行了分析探讨,以期为新形势下沿江城市防洪减灾体系建设提供参考。

近62 a华南“龙舟水”气候特征及变化

每年端午节前后龙舟竞渡之时,是华南前汛期降水最多、最为集中的时段,容易引发严重洪涝灾害,并对早稻生产造成严重影响,称之为“龙舟水”。对华南“龙舟水”期间暴雨过程的频次和强度进行研究是当前防灾减灾的迫切需求。利用1961—2022年华南192个国家气象观测站逐日降水资料,采用EOF、线性趋势、M-K突变等方法,分析了华南“龙舟水”期间降水量的时空特征及变化;构建了一个表征华南“龙舟水”暴雨过程的综合强度指数,由此分析华南近62 a“龙舟水”期间暴雨过程频次、强度以及“龙舟水”强度年景指数的特征和变化。结果表明,华南“龙舟水”一致性变化是其最主要的特点。1961—2022年“龙舟水”期间,华南共出现229次暴雨过程,平均每年3.7次。近62 a来华南区域平均“龙舟水”降水量和暴雨过程频次变化趋势不显著,但“龙舟水”强度年景指数以1.2·(10 a)^(-1)的速率显著上升。评估得到近62 a华南“龙舟水”最强暴雨过程出现在2022年6月4—21日,华南“龙舟水”强年有4 a,分别出现在2022年、2020年、2008年和2006年。

近62 a三峡地区区域性暴雨过程气候特征及长期变化规律

【目的】充分认识三峡地区区域暴雨过程的气候特征及长期变化规律对于科学防汛以及合理利用水资源具有重要意义。【方法】基于三峡地区33个国家级气象观测站1961—2022年逐日降水量资料和目前重庆市气候中心业务采用的区域性暴雨过程监测指标,对三峡地区区域性暴雨过程进行客观识别,并利用多种数理统计方法分析区域性暴雨过程的气候特征和长期变化规律。【结果】结果表明:(1)三峡地区近三分之二的暴雨以区域性过程形式出现,平均每年区域性暴雨过程有8.4次,主要出现在5—9月,尤以6—7月为集中发生时段。区域性暴雨过程首次开始日期多年平均为5月8日,末次结束日期为9月17日。平均每次过程的暴雨覆盖范围为8.6站,持续时间1.3 d,平均暴雨强度为74.7 mm/d。(2)三峡地区区域性暴雨过程年频次存在2~3 a和8 a左右的变化周期,年平均区域性暴雨过程覆盖范围存在4~6 a和8~11 a周期变化。(3)近62 a三峡地区区域性暴雨过程的首次开始日期显著提前,末次结束日期无明显变化,发生期显著变长;发生频次没有明显变化趋势、平均持续时间、平均覆盖范围、平均综合强度也均没有明显变化趋势,但平均暴雨强度呈增强趋势。(4)近62 a,三峡地区区域性暴雨过程的各项指标均未发生突变现象。【结论】研究成果为三峡地区防汛减灾、水资源管理以及回应三峡工程对局地气候影响的社会关切等提供科学支撑。

基于知识图谱的暴雨灾害链挖掘与预测研究

暴雨灾害不仅会引发崩滑流、内涝等次生灾害,更会造成交通中断、供电中断、市政设施损毁等一系列衍生后果,这种现象被称为暴雨灾害链。为了把握暴雨灾害链演化发展的客观规律,有效防范暴雨灾害链的风险,本文提出了一种基于知识图谱的暴雨灾害链挖掘与预测方法。首先,将承灾体影响纳入暴雨灾害链本体模型,构建了暴雨灾害链知识图谱;其次,提出了基于链路耦合的暴雨灾害链挖掘方法,构建了基于贝叶斯网络的暴雨灾害链预测模型;再次,以珠三角地区为例,挖掘暴雨灾害链,并预测某次暴雨事件的灾害链。结果表明:①构建的暴雨灾害链知识图谱能够全面展示出暴雨次生灾害链及其衍生的承灾体后果;②基于知识图谱链路耦合的暴雨灾害链挖掘方法完整地挖掘出了暴雨灾害链,主要类型包括自然灾害类、城市生命线影响类、人员伤亡类、设备和建筑事故类、生产生活潜在影响类;③提出的基于贝叶斯网络的暴雨灾害链预测模型,在暴雨灾害发生初期就能准确预测出暴雨灾害链的发生概率。

陕西三次强致灾性初夏区域性暴雨动力诊断对比分析

利用常规气象观测资料和0.25°×0.25°逐小时ERA5再分析资料,对综合评价强度指数300以上的三次陕西初夏区域性暴雨过程从水汽、动力垂直结构上进行对比分析。结果表明:①强致灾性初夏区域性暴雨发生前,中高层水汽输送来自西南气流,低层来自偏东气流,低层水汽辐合发展加强,动力强迫主要表现为700 hPa以下正涡度区发展加强并向高层延伸,对应200 hPa附近出现强负涡度中心;②暴雨开始后,低层偏东水汽输送在暴雨过程中会发生变化,水汽辐合持续加强并向高层持续输送,散度场出现低层强辐合、高层辐散的结构,而关中有双重辐合-辐散特殊结构,且正涡度区继续向高层延伸、动力抬升促使上升运动延伸至400 hPa及以上;③初夏暴雨陕南动力强迫相比关中较弱,但水汽输送、水汽含量比关中好,降水效率更高、降水总量更大。

面向气候韧性社区建设的北京东四社区暴雨内涝灾害风险研究

利用气候数据和社会经济数据,分析了北京市东四社区降水特征,评估了社区尺度的暴雨内涝灾害风险。研究表明,20世纪80年代以来,东四社区年降水量、极端日降水量、连续5日最大降水量和大雨日数均呈增加趋势,进一步分析暴雨内涝灾害风险空间分布情况,高风险区主要集中在东四社区西北区域,包括东四北大街沿线,东四九条、八条和七条的西段、月牙胡同的部分区域。研究方法和结果可为社区层面的气候韧性城市适应目标、具体规划建设的提出和实施提供参考。

不同天气尺度强迫下陕西暴雨的成因对比

选取常规高空观测资料、地面加密观测资料和ERA5(0.25°×0.25°)再分析资料,对2020年8月4—7日陕西持续性暴雨过程进行诊断分析,并探讨了暴雨发生发展的物理机制。结果表明:暴雨过程分为两个阶段,分别是5日陕北区域暴雨和7日陕西中南部暴雨,二者的环流背景差异显著;5日暴雨的主要影响天气系统是高空槽、低空急流和低涡,中低层急流强且维持时间长,系统涡度大、辐合强,天气尺度强迫强;7日暴雨的主要影响天气系统是短波槽和低层切变,中低层大气风速小,系统涡度小,辐合相对弱,天气尺度强迫较弱。4—5日中低层大气水汽输送强,水汽输送较气候态偏大3~4σ;700 hPa西南急流和850 hPa东南急流给陕北带来充沛的水汽,中低层大气存在明显低涡,大气湿斜压性强,同时低涡南侧有明显锋生,次级环流增强上升运动,水汽在低涡中心及右侧强烈辐合抬升,强降水得以维持;800~700 hPa存在条件对称不稳定,进一步增强上升运动,异常充沛的水汽供应和偏强的低涡造成持续的上升运动是本阶段产生极端大暴雨的主要原因。6—7日陕西中南部水汽输送较弱,水汽辐合强度较小,但本地可降水量大;暴雨区为暖湿大气控制,对流不稳定较强,对流有效位能大,切变线辐合抬升触发对流,降水对流性更强;本阶段强降水较为分散,但雨强大且持续时间短,与地形关系密切。