共查询到20条相似文献，搜索用时 62 毫秒
1.
利用常规观测、自动气象站、多普勒雷达等资料分析珠江三角洲台风龙卷的活动特征及其产生的环境条件。结果表明:台风龙卷发生在6—10月,时间多为10—20时,出现在台风登陆后1.3～21.3 h的时段内;多数龙卷位于台风中心的东北象限,台风中心在广东湛江一广西东南部或北部湾附近时是珠江三角洲龙卷发生的高风险期。高层辐散、低层辐合及中低空强东南急流在珠江口附近叠加是龙卷产生的有利环流背景。强或弱龙卷环境条件的共同特征为低抬升凝结高度、强深层和低层垂直风切变及较大风暴相对螺旋度(SRH),主要差异是强龙卷的深层和低层垂直风切变与SRH更大;相似台风路径下,有/无龙卷环境条件的明显差异在于0～1 km低层垂直风切变和SRH,两值越大出现超级单体或中气旋的可能性越大,龙卷发生概率也就越高。台风龙卷风暴母体属于低质心的微型超级单体风暴;低层有强或中等强度中气旋,有时强中气旋中心伴有龙卷涡旋特征(TVS);龙卷出现在钩状回波顶端或TVS附近。与西风带超级单体龙卷相比,台风龙卷中气旋的尺度更小、垂直伸展高度更低。 相似文献
2.
Alec H. Paul 《大气与海洋》2013,51(1):66-70
Abstract The frequency of tornadoes on the Canadian Prairies is a subject of much current debate. The author questions the traditional view that tornado frequency on the Prairies decreases westwards from southern Manitoba. A study of various sources of information on severe thunderstorm events on both sides of the 49th parallel leads to the conclusion that prairie tornadoes often are not isolated singular cases but rather are members of tornado outbreaks. Tornadoes in the northern Great Plains and Prairies are more frequent than has previously been thought, and are likely to be under‐reported compared with those of “tornado alley” in the United States. The Prairie Region can validly be regarded as an outlying section of the North American tornado belt. 相似文献
3.
闪电活动对于强龙卷天气的发生有一定的指示作用,基于闪电定位资料,结合多普勒天气雷达、探空和ECMWF再分析资料对两次典型强龙卷风暴中地闪的时空演变、雷电流强度及正地闪活动特征进行了统计分析,结果表明:地闪主要发生在组合反射率因子≥30 dBZ的区域内,龙卷发生期间,地闪活动减弱且较为分散。不同龙卷风暴的地闪频次差异较大,这与风暴中上升气流的强度有关;当地闪频次从峰值降至最小值期间,龙卷及地,两次过程中地闪频次峰值分别提前龙卷发生约33 min和28 min。同时,龙卷及地之前,地闪会出现连续多次闪电跃增;龙卷等级越强,正地闪表现越活跃,特征越明显,在江苏盐城阜宁龙卷发生期间,还出现了地闪极性从正地闪主导向负地闪主导的反转;两次龙卷风暴雷电流强度随时间的变化规律并不明显,但均小于历史平均值,地闪发生愈频繁的龙卷风暴,对应的雷电流强度值愈小。 相似文献
4.
After several decades of little work, a revised tornado climatology for Austria is presented. Tornadoes seldom form in the alpine areas, however, near the eastern flanks of the Alps, favourable conditions for tornado genesis are found. Whereas in the alpine regions less than 0.3 tornadoes per 10,000 km2 a year touch down (averaged for provinces or major parts of a province), we can count 0.9 in the greater Graz area, 1.0 in the greater Linz area and 1.2 tornadoes per 10,000 km2 a year in the greater Vienna area, suggesting the existence of so-called tornado alleys. As these regions are the most populated areas of Austria, there is a possible population bias in the dataset. The overall average for Austria is 0.3 tornadoes per 10,000 km2 a year.The database consists of 89 tornadoes, one landspout and six waterspouts, with a total of 96 events. The seasonal peak is in July with a maximum probability of tornadoes in the late afternoon and early evening hours. Every fifth tornado occurs in the hour after 5 p.m. The maximum intensity determined for a tornado in Austria was T7 on the TORRO-Scale (F3 on the Fujita-Scale), the most common intensity is T2 on the TORRO-Scale (F1 on the Fujita-Scale). 相似文献
5.
0808号台风凤凰前部龙卷的环境场和雷达回波分析 总被引：5，自引：0，他引：5
用多普勒天气雷达、常规观测和地面加密观测资料对2008年7月29-30日发生在江苏的台风凤凰前部系列龙卷过程进行了详细分析.结果如下:该龙卷发生在台风前部风切变区里,低空较强的垂直风切变、极不稳定的大气层结和深厚的正涡度区,为龙卷的发生提供了热力和动力条件.龙卷回波的反射率因子特征表现为最大反射率因子梯度位于回波的后侧,一般都有弱回波区和后侧入流缺口相伴随.东台龙卷产生于飑线型弓形回波的顶点,具有相对较大的反气旋性切变.高邮龙卷中低层具有弱的气旋性涡旋,宝应龙卷回波的内部环流特征明显,有明显的中气旋结构.在业务工作中,强回波质心高度和垂直累积液态含水量的骤降、径向速度风场中气旋性涡旋的迅速发展是对龙卷的提前警戒很好的参考指标. 相似文献
6.
利用1976—2005年江苏省龙卷信息化资料和高分辨率再分析资料,对江苏省龙卷的发生特征以及ENSO事件对江苏省龙卷发生数的影响进行了分析。结果表明:(1)1976—2005年,江苏省龙卷发生数年际和年代际变化明显,空间分布不均匀:1990s龙卷发生数较多;盐城南部和南通沿海地区是龙卷较为多发的区域。(2)ENSO事件对江苏省龙卷的发生频率有重要影响:ENSO冷事件月份平均龙卷发生数多于暖事件月份;非ENSO事件月份平均龙卷发生数居中。(3)ENSO冷事件时西南低空急流发生频率明显增加,由于低空急流增强而引起的江苏省地区水汽供应、动力条件和不稳定能量的分布均有利于龙卷的发生,导致在ENSO冷事件情况下江苏省龙卷发生数偏多。 相似文献
7.
8.
Tornadoes have occurred in the territory of the Czech Republic throughout history. Although their frequency and intensity are not as high as in the USA, they can cause severe damage as well. That is why a systematic effort to document individual occurrences of this dangerous meteorological phenomenon as far as possible back into the past began in the 1990s. The aim of this investigation is to extend the first European catalogue of tornadoes originally published by Wegener [Wegener A., 1917. Wind-und Wasserhosen in Europe], by the addition of these cases from the Czech Republic.This paper adds further to Setvák, Šálek and Munzar [Setvák M., Šálek M., Munzar J., 2003. Tornadoes within the Czech Republic—from medieval chronicles to the internet society. Atmos. Res. 67–68, 589–605], who reported the earliest documented tornado in the land of the Czech Republic which occurred in AD 1119 in Prague. In so doing, it presents recently discovered tornado cases from the 16th to the early 20th centuries, found in a variety of historical sources since the last ECSS conference held in Prague in 2002. In particular we will focus on the case from Jablonec nad Nisou (northern Bohemia) in 1925, which was probably the first case in the Czech Republic with accompanying photographic documentation of damage caused by a tornado. 相似文献
9.
根据中国气象灾害大典、年鉴、全国与河南省气候影响评价等文献,对豫东南区域1949-2011年30次龙卷风的历史记录逐个进行了时空分析和富士达分级：63 a来发生于6、7月的龙卷风占总次数的2/3;20世纪80年代集中发生在1984年和1986年,90年代仅1990、1993年没有发生,21世纪前10 a主要是2005年的3次（均为F1级）。有24个县（市）曾有龙卷风光顾过,发生最多的汝南和潢川曾遭遇过5次龙卷风袭击,其他县（市）分别出现1～4次不等。灾害特征是较低级别的F0和F1等级较多,F2等级较少,但发生的概率和强度等级均高于豫西。 相似文献
10.
An outbreak of powerful tornadoes tore through multiple states in the central and southern United States from 10 to 11 December 2021. It is claimed the deadliest tornado outbreak that has taken place on December days. The National Oceanic and Atmospheric Administration had confirmed 66 tornadoes as of 21 December, producing at least 90 fatalities. Most tornadoes occurred at night and thus they were difficult to be visually located, which directly increases the risk for local residents. Two 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 performance. This tornado outbreak has aroused extensive discussion from both the public and the research community in China. This paper presents a brief discussion on the formation environment and warning services of the tornado outbreak. Recall 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 cases. Some views on the tornado warning issuance and receiving and damage surveys in China are also presented. 相似文献
11.
Franois Paul 《Atmospheric Research》2001,56(1-4)
The analysis of 304 French tornadoes shows that the most struck areas are the northwestern part of the country, the south and the east. Tornadoes occur mainly in spring and in summer; August is the month when the frequency is maximum. Tornadoes move mainly from southwest to northeast, except in the south where the direction is sometimes south to north. Thirty-six killer tornadoes were listed (12% of the cases); most of them with an intensity greater or equal to F3. The occurrence is approximately 15–20 tornadoes each year in France, and the annual risk probability of significant tornadoes in France is 0.66×10−5. This value is probably underestimated because all the tornadoes are not listed. 相似文献
12.
Dan Yao Haile Xue Jinfang Yin Jisong Sun Xudong Liang Jianping Guo 《Acta Meteorologica Sinica》2018,32(2):157-171
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 m s–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. 相似文献
13.
中国龙卷时空分布及其环境物理量特征 总被引：6，自引：2，他引：6
利用2004—2012年《中国气象灾害年鉴》和CFSR再分析资料,研究中国龙卷的时空分布以及三个龙卷频发区的环流背景场和环境物理量特征,并比较他们之间的区域差异。结果表明:中国龙卷多发生于春夏季,午后傍晚较多,江苏和广东等平原地区出现龙卷概率最高。龙卷临近时,“江苏及其邻近地区”位于500 hPa槽前,850 hPa上有西南急流,造成了较强的低层垂直风切变;“广东及其邻近地区”在龙卷发生前地面对流有效位能均值达997.3 J/kg,0~1 km螺旋度均值达91 m2/s2,层结不稳定,动力抬升强;“东北地区”受深厚东北冷涡控制,整层水汽含量低,中低层比湿均值小于10 g/kg。通过比较环境物理量平均场的分布特征发现:螺旋度、垂直风切变、能量螺旋度指数和强龙卷参数对分析龙卷发生有很好的指示意义。“东北地区”对流有效位能和比湿均值远低于“江苏及其邻近地区”和“广东及其邻近地区”,但高低空的温度直减率大、中低层的垂直风切变强,该地区也会产生龙卷。 相似文献
14.
京津冀区域龙卷风灾害特征分析 总被引：1，自引：0，他引：1
基于气象报表、中国气象灾害大典、气象灾情数据库以及档案馆地方志等历史资料,查阅1956—2016年京津冀区域的龙卷风个例,按照"增强藤田级别"龙卷风强度等级分类标准,采用专家评定法对龙卷风个例进行定级,并运用时间序列、趋势分析和空间分析方法,对龙卷风的时空分布、灾害特征进行了统计分析。主要结论如下:①1956—2016年,京津冀区域共确认龙卷风个例188个,空间分布上,龙卷风发生最多的区域有2个,一是张家口坝上4县:张北、尚义、沽源、康保,二是京津冀东部地区,特别是沧州、天津、唐山、秦皇岛沿海地区是龙卷风高发区;②时间分布上,1985—1993年龙卷风发生次数最多,90年代以后呈下降趋势;③龙卷风在夏季发生次数占总数的81.9%,龙卷风主要发生时段为11:00—20:00;④对有灾情记录的122个龙卷风个例,经专家评定,EF4和EF3级各1例,EF2级14例,EF1级52例,EF0级54例。 相似文献
15.
The Tornado and Storm Research Organisation (TORRO) was formed in the UK in 1974 in order to determine realistic spatial, temporal and intensity distributions of tornadoes in the UK and, eventually, throughout Europe. Currently, TORRO's databases contain nearly 2000 tornadoes and over 550 waterspouts for the UK alone. In 1972, TORRO's founder, Terence Meaden, devised the Tornado Intensity Scale. This scale enables the wind speeds of tornadoes to be rated on a scale from T0 to T10, or more (since it is an open-ended scale). Using this scale, estimates have been made of the statistical return periods of differing intensities of UK tornadoes. TORRO's research into understanding the conditions of tornado development is ultimately intended to lead to issuing forecasts of tornadoes. In 1991, TORRO issued the first tornado watch in the UK for 12 November and this proved to be accurate—not only did three property-damaging tornadoes strike East Anglia but the forecast maximum intensity of T5 was attained. In 1975, TORRO expanded its activities to include conventional thunderstorm reporting and investigations. In 1982, TORRO incorporated the British and Irish thunderstorm data-collection organisation, the Thunderstorm Census Organisation (TCO), which was established in 1924. By the early 1980s, TORRO's network of voluntary thunderstorm observers, located throughout the UK and Ireland and increasingly in other European countries, numbered around 350 and the network continues to grow. In addition to TORRO's early focus on tornadoes and thunderstorms, its data collection and research has expanded to consider other whirlwinds (such as waterspouts and land devils), hailstorms, lightning (including ball lightning) and blizzards/heavy snowfalls. In 1996, TORRO began providing easy access to its databases (e.g. post-1995 UK and European severe weather events, especially tornadoes and hailstorms) and other information via its internet site at http://www.torro.org.uk/. Building on over 25 years of experience—and of the half a century of the TCO before it—TORRO continues to expand its European role in severe weather data collection and research, helped by the on-going appointment of European representatives and its increasing European membership. 相似文献
16.
利用欧洲中期天气预报中心ERA5再分析数据, 统计1979—2020年辽宁省42个温带气旋龙卷环境背景和物理量参数特征, 结果表明:辽宁省温带气旋龙卷多发于温带气旋中心的西南、东南象限, 与冷锋前暖区相对应, 主要分布在辽河平原中西部及渤海湾沿岸, 强龙卷(EF2及以上级别)占比为28.6%。风暴相对螺旋度和对流有效位能的大值区出现在气旋西南—东南象限, 呈带状分布, 龙卷风暴主要分布于风暴相对螺旋度大值区西北侧、对流有效位能大值区的顶端的强梯度区附近。强龙卷参数最大值达0.7, 其大值区与EF2及以上级别龙卷相对应。地面冷锋和干线是温带气旋龙卷的关键触发系统, 对比近气旋中心和冷锋尾部湿度垂直分布, 后者所表现的高层强干侵入导致风暴产生更强的冷池, 过强的下沉气流可能是龙卷产生的不利因素。温带气旋龙卷多分布于高空急流左侧气流的分流区内, 对应高空强辐散区。0~3 km垂直温度递减率大值区与气旋中心附近的弱龙卷高发区有较好对应关系。 相似文献
17.
近年来我国极端灾害性天气频发,造成了重大人员伤亡和财产损失,随着防灾减灾工作的推进,龙卷等中小尺度强对流灾害性天气的预警预报工作的关注度正逐步提升。现有龙卷检测算法基于对新一代天气雷达基数据在多个仰角和体积扫描中进行阈值判断得到龙卷涡旋特征TVS,在自适应协同观测背景下表现为自适应策略同步较慢,预警预报准确率不高,提前预警时间短。使用机器学习算法结合龙卷在雷达反射率、径向速度和速度谱宽的多重特征能有效提高龙卷识别的准确率和预警时间,能提高组网雷达的协同观测能力。基于随机森林的龙卷检测算法（TDA-RF）,使用CINRAD雷达历史龙卷数据作为训练集,通过随机森林算法对训练集进行分类学习得到龙卷预测模型,使用预测模型对实时雷达数据进行龙卷检测。试验结果表明,TDARF算法能有效识别不同强度的龙卷,较TVS龙卷检测算法能给出龙卷区域的分类概率值,无需对龙卷特征时空连续性进行判断;TDA-RF算法对多个特征进行综合判断具有较好的抗干扰能力,使基于组网雷达的龙卷预警时间最高可达18分钟。 相似文献
18.
In the Balearic Islands, located in the Western Mediterranean, 27 tornadoes and 54 waterspouts have been recorded during the period 1989–1999. A climatology focusing, which focuses on path length, F-scale velocity, season and time of occurrence, is presented. September and October appear to be the months with the highest frequency of appearance. The environment in which thunderstorm producing tornadoes and waterspouts developed has been analysed. Main thermodynamic stability indices reveal that no specific conditions are required for the tornado and waterspout genesis. It is also found that these events form in air masses colder than that indicated by the climatology of the region. Analyses of helicity and CAPE demonstrate that, in most of the cases, the environments were not favourable for mesocyclone formation and supercell development. 相似文献
19.
Stanley A. Changnon 《Climatic change》2011,106(2):129-140
The temporal distributions of the nation’s four major storm types during 1950–2005 were assessed, including those for thunderstorms,
hurricanes, tornadoes, and winter storms. Storms are labeled as catastrophes, defined as events causing $1 million or more
in property losses, based on time-adjusted data provided by the insurance industry. Most catastrophic storms occurred in the
eastern half of the nation. Analysis of the regional and national storm frequencies revealed there was little time-related
relationship between storm types, reflecting how storm types were reported. That is, when tornadoes occurred with thunderstorms,
the type producing the greatest losses was the one identified by the insurance industry, not both. Temporal agreement was
found in the timing of relatively high incidences of thunderstorms, hurricanes, and winter storms during 2002–2005. This resulted
in upward time trends in the national losses of hurricane and thunderstorm catastrophes, The temporal increase in hurricanes
is in agreement with upward trends in population density, wealth, and insurance coverage in Gulf and East coastal areas. The
upward trends in thunderstorm catastrophes and losses result from increases in heavy rain days, floods, high winds, and hail
days, revealing that atmospheric conditions conducive to strong convective activity have been increasing since the 1960s.
Tornado catastrophes and their losses peaked in 1966–1973 and had no upward time trend. Temporal variability in tornado catastrophes
was large, whereas the variability in hurricane and thunderstorm catastrophes was only moderate, and that for winter storms
was low. 相似文献
20.
对2009—2016年江苏北部龙卷事件的环境场进行统计与诊断,并对两次典型龙卷过程环境场进行数值模拟,重点探讨近海岸平原地区的江苏北部在春夏季节成为中国强龙卷最高频发生地的特殊性以及环境双锋面系统相遇对龙卷环境场的增强机制。分析结果显示：苏北龙卷发生率占全省58.6%。其中盐城和徐州又是苏北龙卷最高发地区。春夏季节,冷暖干湿气团势力相近,中尺度锋面系统多,易发生双锋面汇集造成局地龙卷强对流。对徐州（2009年）和盐城（2016年）的两次典型龙卷强对流环境场分析显示,徐州龙卷为变形场锋生和海风锋汇合,盐城龙卷为气旋锋面和岸滨锋相遇。WRF模拟结果显示,双锋面系统汇聚以及锋面二级环流相遇,可造成局地水平风速垂直扭转及垂直速度的水平切变,有利于驱动和增强区域正涡度;双锋面二级环流垂直上升支的叠加,可在平坦地区产生强烈的系统性抬升。这将形成有利龙卷类强对流天气发生发展的环境场。而各种常用的强对流指标均具有较强局地性,需要依据局地统计特征进行参考使用。 相似文献