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Tubular limiting stream surface: “tornado” in three-dimensional vortical flow

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Applied Mathematics and Mechanics(English Edition) 2018年第11期39卷 1631-1642页

作者： Shuhai ZHANG State Key Laboratory of Aerodynamics China Aerodynamics Research and Development Center

A new physical structure of vortical flow, i.e., tubular limiting stream surface(TLSS), is reported. It is defined as a general mathematical structure for the physical flow field in the neighborhood of a singularity, and has a close relationship with limit *** TLSS is a tornado-like structure, which separates a vortex into two regions, i.e., the inner region near the vortex axis and the outer region further away from the vortex *** flow particles in these two regions can approach to(or leave) the TLSS, but never could reach it.

关键词： tubular limiting stream surface tornado three-dimensional(3D) vortical flow

Investigation into the Formation, Structure, and Evolution of an EF4 tornado in East China Using a High-Resolution Numerical Simulation

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Journal of Meteorological Research 2018年第2期32卷 157-171页

作者： Dan YAO Haile XUE Jinfang YIN Jisong SUN Xudong LIANG Jianping GUO State Key Laboratory of Severe Weather Chinese Academy of Meteorological Sciences

Devastating tornadoes in China have received growing attention in recent years, but little is known about their formation, structure, and evolution on the tornadic scale. Most of these tornadoes develop within the East Asian monsoon regime, in an environment quite different from tornadoes in the U.S. In this study, we used an idealized, highresolution（25-m grid spacing） numerical simulation to investigate the deadly EF4（Enhanced Fujita scale category 4）tornado that occurred on 23 June 2016 and claimed 99 lives in Yancheng, Jiangsu Province. A tornadic supercell developed in the simulation that had striking similarities to radar observations. The violent tornado in Funing County was reproduced, exceeding EF4（74 ms–1）, consistent with the on-site damage survey. It was accompanied by a funnel cloud that extended to the surface, and exhibited a double-helix vorticity structure. The signal of tornado genesis was found first at the cloud base in the pressure perturbation field, and then developed both upward and downward in terms of maximum vertical velocity overlapping with the intense vertical vorticity centers. The tornado＇s demise was found to accompany strong downdrafts overlapping with the intense vorticity centers. One of the interesting findings of this work is that a violent surface vortex was able to be generated and maintained, even though the simulation employed a free-slip lower boundary condition. The success of this simulation, despite using an idealized numerical approach, provides a means to investigate more historical tornadoes in China.

关键词： tornado Cloud Model version 1(CM1) vertical vorticity updraft helicity double-helix structure hazardous wind

Rapid-Scan and Polarimetric Phased-Array Radar Observations of a tornado in the Pearl River Estuary

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Journal of Tropical Meteorology 2021年第1期27卷 81-86页

作者： ZHANG Yu BAI Lan-qiang MENG Zhi-yong CHEN Bing-hong TIAN Cong-cong FU Pei-ling Guangzhou Meteorological Observatory China Meteorological AdministrationGuangzhou 511430 China School of Atmospheric Sciences/Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies Sun Yat-sen UniversityZhuhaiGuangdong 519082 China Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai) ZhuhaiGuangdong 519082 China Department of Atmospheric and Oceanic Sciences School of PhysicsPeking UniversityBeijing 100871 China

The strong destructive winds during tornadoes can greatly threaten human life and destroy *** increasing availability of visual and remote observations,especially by Doppler weather radars,is of great value in understanding tornado formation and issuing warnings to the *** this study,we present the first documented tornado over water detected by a state-of-the-art dual-polarization phased-array radar(dual-PAR)in *** contrast to new-generation weather radars,the dual-PAR shows great advantages in tornado detection for its high spatial resolution,reliable polarimetric variables,and rapid-scan *** polarimetric signature of copolar cross-correlation coefficient with anomalously low magnitude appears to be effective for verifying a tornado and thus is helpful for issuing tornado *** Guangdong Meteorological Service has been developing an experimental X-band dual-PAR network in the Pearl River Delta with the goal of deploying at least 40 advanced dual-PARs and other dual-polarization weather radars before *** network is the first quasi-operational X-band dual-PAR network with unprecedented high coverage in the *** such high-performance close-range PARs,efficient operational nowcasting and warning services for small-scale,rapidly evolving,and damaging weather(e.g.,tornadoes,localized heavy rainfall,microbursts,and hail)can be expected.

关键词： tornado waterspout phased-array radar dual-polarization China

A Brief Discussion on the High-impact Cold-season tornado Outbreak During 10-11 December 2021 in the United States

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Journal of Tropical Meteorology 2022年第2期28卷 252-260页

作者： LI Cai-ling BAI Lan-qiang YU Xiao-ding TAN Hao-bo HUANG Xian-xiang YAN Li-jun LI Zhao-ming ZHANG Ze-yu Foshan tornado Research Center Foshan Meteorological ServiceFoshanGuangdong 528000 China Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai) ZhuhaiGuangdong 519082 China China Meteorological Administration Training Center Beijing 100081 China Guangdong Meteorological Service Guangzhou 510062 China

An outbreak of powerful tornadoes tore through multiple states in the central and southern United States from 10 to 11 December *** is claimed the deadliest tornado outbreak that has taken place on December *** National Oceanic and Atmospheric Administration had confirmed 66 tornadoes as of 21 December,producing at least 90 *** tornadoes occurred at night and thus they were difficult to be visually located,which directly increases the risk for local *** violent nighttime tornadoes were rated category 4 on the enhanced Fujita scale(EF4).Although a high death toll was caused during this event,the operational service actually presented an excellent *** tornado outbreak has aroused extensive discussion from both the public and the research community in *** paper presents a brief discussion on the formation environment and warning services of the tornado *** the deadliest violent tornado in the past 45 years in China,the radar-based tornadic vortex signatures at the locations with EF4 damages show a comparable strength with those in the current *** views on the tornado warning issuance and receiving and damage surveys in China are also presented.

关键词： tornado tornado outbreak severe weather cold season warning service

Investigation of effects of hazard geometry and mitigation strategies on community resilience under tornado hazards using an Agent-based modeling approach

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Resilient Cities and Structures 2024年第2期3卷 1-19页

作者： Xu Han Maria Koliou Postdoctoral Research Associate Zachry Department of Civil and Environmental EngineeringTexas A&M UniversityCollege StationTXUSA Associate Professor Zachry Department of Civil and Environmental EngineeringTexas A&M UniversityCollege StationTXUSA

A large number of communities are impacted annually by the increasing frequency of tornado hazards resulting in damage to the infrastructure as well as disruption of community *** effect of the hazard geometry(center and angle of tornado path as well as the tornado width)is studied herein on how it influences the recovery of physical and social systems within the *** that pre-disaster preparedness including mitigation strategies(e.g.,retrofits)and policies(e.g.,insurance)is crucial for increasing the resilience of the community and facilitating a faster recovery process,in this study,the impact of various mitigation strategies and policies on the recovery trajectory and resilience of a typical US community subjected to a tornado is investigated considering different sources of *** virtual testbed of Centerville is selected in this paper and is modeled by adopting the Agent-based modeling(ABM)approach which is a powerful tool for conducting community resilience analysis that simulates the behavior of different types of agents and their interactions to capture their *** results are presented in the form of recovery time series as well as calculated resilience indices for various community systems(lifeline networks,schools,healthcare,businesses,and households).The results of this study can help deepen our understanding of how to efficiently expedite the recovery process of a community.

关键词： Community resilience Agent-based modeling(ABM) tornado Mitigation strategy

tornado’s Compressibility

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Natural Science 2020年第4期12卷 218-220页

作者： Kern E. Kenyon 4632 North Lane Del Mar USA

An earlier fluid mechanical model of a tornado [1], that assumed constant air density, forecast a horizontal rotary wind speed that decreased inversely as the distance increased from the tornado’s central axis. Such a velocity function implies that the force of friction is zero. However, if compressibility of the air is included in the model, and everything else is kept the same, dynamics changes the velocity structure to being constant and independent of the radius. Friction is also zero in this case. Observations are needed to find out what the wind structure is doing.

关键词： tornado Compressibility

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基于tornado的嵌入式软件单元测试

计算机工程与设计 2012年第7期33卷 2683-2689页

作者：王泉中国航空西安软件测评中心陕西西安710068

根据嵌入式软件特点,提出一种基于tornado开发环境的嵌入式软件单元测试方法。该测试方法使用Testbed/Tbrun自动测试工具,借助Tbconfig辅助工具完成tornado环境下的测试配置,保持测试环境和开发环境的一致性;使用黑/白盒结合的隔离单元... 详细信息

根据嵌入式软件特点,提出一种基于tornado开发环境的嵌入式软件单元测试方法。该测试方法使用Testbed/Tbrun自动测试工具,借助Tbconfig辅助工具完成tornado环境下的测试配置,保持测试环境和开发环境的一致性;使用黑/白盒结合的隔离单元测试技术提高测试用例设计质量,快速达到结构覆盖率要求;定制测试报告模板,使用TbrunRe-porter完成测试报告自动生成。该测试方法使测试工作的重心转移到测试用例的设计和执行上,减少代码移植和手动测试报告生成等冗余工作量,极大提高测试效率和测试规范性,已作为一种通用的嵌入式软件单元测试方法在所在测评机构加以推广使用。

关键词： tornado 嵌入式软件单元测试 Testbed/Tbrun 结构覆盖率

Associations of Jet Streams with tornado Outbreaks in the North America

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Atmospheric and Climate Sciences 2015年第3期5卷 336-344页

作者： Igor G. Zurbenko Mingzeng Sun Department of Epidemiology and Biostatistics State University of New York at Albany New York USA

Jet streams, a current of fast winds located about seven miles up near the tropopause, are major weather driving factors in the mid-latitudes. Using the Modern-Era Retrospective Analysis for Research and Applications (MERRA) reanalysis data resources for the period 1979 to 1988, we defined the latitudinal distribution of daily wind maxima by month, and analyzed latitudinal distribution of the highest daily wind speed at the selected longitude in the 19th week of the year. We showed the typical diving pattern of jet stream over Central America in spring. We found that latitudinal distribution of daily wind maxima was concurrently oscillated with latitudinal distribution of tornado outbreaks in April, May and June. KZ filter smoothed latitudinal distribution of highest daily wind speed on tornado days showed a substantial increase in number of daily wind maxima over tornado alley region, compared to that on non-tornado-days.

关键词： Jet Stream tornado KZ Filter Specific Humidity

ON　ENVIRONMENTAL　CONDITIONS　OF　THE　GENESIS　OF　tornado　IN　THE　ZHUJIANG　RIVER　DELTA　IN　SPRING

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Journal of Tropical Meteorology 1996年第1期2卷 98-103页

作者：王沛霖

Using observational data and the data of disastrous investigation of tornado in Zhujiang River Delta and Guangzhou's sounding from March to May of 1976-1983, the environmental conditions of genesis of tornado are analysed and compared with those of nontornadic local storm. It is found that the favorable conditions of genesis of tornado are lower pressure, unstable stratification and stronger wind in the deep layer of troposphere and higher temperature and humidity in low level, among which, lower pressure, more unstable stratification and layer wind are primary conditions for a severe local storm to possibly develop into a storm with accompanying tornado. The tornado mechanism is not related to vertical wind shear.

关键词： Zhujiang River Delta spring tornado environmental condition