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2010年6月中下旬南方暴雨过程变形场作用分析 总被引：3，自引：2，他引：1
利用常规原始报文资料,采用基于Lanczos窗口滤波器的合成分析方法,对2010年6月13-27日的形势场、物理量进行合成分析,计算并分析了低空合成风场的总变形.结果表明:500 hPa大陆中、高纬地区存在一“Ω”形类阻塞高压,西北冷空气从其东部源源不断向长江及以南地区输送,与副热带高压西北侧的西南暖湿气流在我国南方地区交汇.700、850 hPa大陆高压与西太平洋副热带高压之间形成的鞍型场,位于长江以南地区,鞍型场鞍点附近及其东部膨胀轴是暴雨发生的主要区域.在南方地区上空200 hPa西北气流辐散产生的抽吸作用,对这次长时间、高强度的降水起了重要作用.发生在鞍型场和切变线上的低空中尺度气旋,是造成暴雨的重要天气系统.鞍型场膨胀轴附近,总变形最大,其位置、走向均与雨带基本一致,有利于锋生和中尺度气旋形成.低空冷暖气流交汇区域形成低空强θse梯度,在垂直剖面图上,等θse线呈现十分倾斜状态,该区域强θse水平梯度与低空总变形、正涡度区一致,可能是特大暴雨发生的重要因素. 相似文献
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2012年7月中旬克拉玛依罕见强对流天气的数值模拟分析 总被引：1，自引：1，他引：0
本文利用NCEP—FNL分析资料、自动站观测资料、卫星云图、天气雷达探测资料以及WRF模式的模拟结果,对2012年7月14日新疆克拉玛依罕见的短时强降雨和冰雹强对流天气的机理进行了诊断分析,结果表明:在大尺度湿性不稳定层结的环境场中,冷空气的入侵在山区地形配合下,在背风坡侧造成强烈的水平温度梯度和地面辐合线,利于强对流的发生。WRF模拟结果显示,高低空风速大值区的配置,环境风场的垂直切变,垂直方向上假相当位温的鞍形配置给垂直上升运动的加强提供基础,使最大上升速度达到6.5 m·s~(-1),上升高度达9 krn,同时也看到,由于中层湿中性层结较薄,难以长时间维持上升运动的发展,上升运动区较为窄小,强降雨发生区域仅为二十几千米。山区地形对强对流发展的作用较为复杂但也很明显,地形阻挡加强了地面风场的切变辐合,同时气流过山引发正负位势涡度带的生成和传播,激发垂直环流的形成,为强对流发展提供动力条件。 相似文献
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利用2010年7月22日苏皖中尺度对流复合体（MCC）数值模拟输出结果,考察了模式对MCC的模拟能力,并对模拟结果做了动力和热力诊断分析,以揭示盛夏江淮下游MCC的特征。结果表明：1） 三重嵌套网格距为3.3 km的区域WRF模式的模拟效果较佳,结果与实况一致,并可利用模拟降水的范围及强度来确定MCC的位置及演变。2） 此MCC维持约10 h,其南北不对称,并随西太平洋副热带高压西伸北抬而随之北抬。MCC核心区对流层低层有水汽丰沛的入流,并有强辐合区,呈对流不稳定层结;中层有深厚的强上升运动,并因凝结潜热大量释放呈中性层结;高层则有出流;MCC核心区对流降水非常强。3） 在垂直剖面上,该核心区散度存在中低层辐合、高层辐散的柱状结构,此配置有利于强对流维持和加强,中低层以上有深厚的强上升气流柱,这些都是MCC核心区存在强对流的标志。该MCC的螺旋结构表明其中的强对流高度有组织。 相似文献
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本文在已有研究基础之上,利用2004年9月1～6日川东地区暴雨过程的观测资料,从大尺度环流、水汽输送和温度平流,并利用湿位涡的垂直和水平分量（Pm1和Pm2）以及相当位温诊断分析并验证川东暴雨发生的＂鞍＂型大尺度环流背景特征以及西南涡发展的物理过程,其结果表明如下：（1）在此次暴雨发生期间,仍存在显著＂鞍＂型大尺度环流配置;（2）在＂鞍＂型场大尺度环流背景下,强西南气流绕流高原东侧直接进入四川盆地,而弱西南气流则绕流云贵高原输送进入四川盆地东部,受地形的阻挡和西伸的西太平洋副高的作用在四川盆地东部形成向北的急流辐合带,同时,由于两支气流输送着大量的水汽,暖湿空气在川东地区形成高温高湿的辐合区;（3）在＂鞍＂型场作用下,盆地上空的低层不断聚集季风气流输送的大量暖湿空气,而在高层有两股冷干空气侵入,从而导致了盆地内低涡系统强烈发展,由湿位涡的诊断表明了在暴雨发生期间,在四川盆地北部上空的高层不断有干空气入侵,引起了垂直对流不稳定,即Pm1〈0,并向盆地东北部发展,从而使此区域气旋性涡度不断加强,即低涡强烈发展;并且,在盆地上空低层暖湿空气相当位温的水平梯度对于西南低涡的发展和暴雨的发生同样起了重要作用,正的Pm2中心与暴雨发生区域有很好的一致性,这表明暴雨往往发生在高温高湿的强垂直不稳定区域;（4）＂鞍＂型场大尺度环流背景、孟加拉湾及南海水汽输送辐合、川北冷空气侵入,西南低涡发展是川东暴雨发生的共同特征。 相似文献
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利用MICAPS资料、多普勒天气雷达资料和NCEP资料等,对2013年7月25日黄土高原一次引发短时致洪暴雨MCC的特点及成因进行了分析。结果表明:300hPa天气尺度反气旋和500hPa天气尺度西南气流是MCC在对流层中上层的直接影响系统,700hPa α-中尺度横切变和850hPa副热带高压西侧α-中尺度低涡是MCC在对流层低层的直接影响系统;地面湿焓场低值舌的活动是MCC触发机制之一;地面湿焓场≥40℃高值中心区和MCC生成区相对应;MCC生成区在径向速度场上出现西南低空急流的生成和维持、逆风辐合区的生成和维持,低层辐合和高层强辐散的配置,为MCC的生成及暴雨的形成提供了动力条件;冷暖平流的配置也为MCC生成和东移发展创造了有利条件;空间剖面图上看到的湿螺旋度高值带对MCC生成发展和东移具有指示意义。 相似文献
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“96·8”特大暴雨和中尺度系统发展结构的非静力数值模拟 总被引：11，自引：0，他引：11
1996年 8月 3～ 5日 (“96· 8”) ,中国河南、山西、河北等省发生了一次特大暴雨过程 ,造成了严重洪涝灾害。文中的天气分析指出 ,稳定的大型鞍形场和北移台风 (登陆后减弱为低压 )与其东侧副热带高压的相互作用是“96· 8”特大暴雨发生的大、中尺度环流条件 ;而中尺度低压及其特有的动力热力结构与该暴雨过程直接相关。对该过程采用非静力中尺度数值模式 (MM5)进行了数值模拟研究。模拟结果分析发现 ,非静力 (MM5)的全物理过程模拟基本上可再现大尺度和中 -α尺度天气系统的发生、发展和演变。采用二重网格双向嵌套技术的细网格模拟结果揭示 ,低压的动力场和热力场之间具有一种强耦合机制 ,即发展的低压具有气旋性涡柱的暖心高湿结构 ,在涡柱低空是湿对流不稳定和负湿位涡结构 ;强垂直上升运动与高空强辐散和低空强辐合以及对流云团的发展互耦 ;与低压相伴的强南风急流不仅是低压和对流云团发展与维持的互伴互耦条件 ,而且也是“96· 8”特大暴雨的水汽源和热能输送带。降水模拟结果分析表明 ,尽管某些降水中心对粗网格偏小 ,对细网格偏大 ,但雨带和雨强分布与观测结果基本一致。 相似文献
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黄河中游一次MCC致洪暴雨综合诊断分析 总被引：2，自引：0，他引：2
为了提高对MCC致洪暴雨的预报和预警能力,利用卫星云图、MICAPS系统提供的资料以及多普勒雷达资料,对2006年7月2日黄河中游发生的一次中尺度对流复合体(MCC)和黄河中游暴雨天气过程进行了大尺度环境场和物理量的诊断分析以及三维流场结构分析.结果表明:MCC是造成暴雨的直接影响系统;对流层中低层深厚暖湿切变辐合的形成,配合对流层高层急流分支出口处生成中-α尺度强辐散、对流层低层华北冷空气南下倒灌锋生产生的动力抬升作用,形成有利于MCC生成发展的环流背景;MCC发生在高能、弱对流不稳定区;700hPa西南低空急流、850hPa分支南风气流为MCC的生成发展提供了充足的水汽和能量;涡度场和散度场的耦合、强烈上升运动的形成,成为MCC发生发展和维持的动力机制;多普勒雷达径向速度场显示,东南低空急流、配合西南低空急流的生成和稳定,西南低空急流左侧有气旋性辐合的维持、配合对流层中高层径向强辐散,构成MCC致洪暴雨的三维流场结构. 相似文献
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中尺度天气的高空地面综合图分析 总被引：6，自引：4，他引：2
中尺度强天气的预报能力非常有限,一个重要原因是在业务预报中,缺乏对中尺度对流天气发生的环境场条件和发生发展特征进行及时有效的分析。本文介绍了国家气象中心正在试行的中尺度天气的天气图分析方法。中尺度天气的天气图分析主要利用探空资料和数值预报相关参量资料,分析中尺度对流天气发生发展的环境场条件,包括高空综合图分析和地面分析。在高空分析中重视风、温度、湿度、变温、变高的分析,并通过将不同等压面上最能反映水汽、抬升、不稳定和垂直风切变状况的特征系统和特征线绘制在一张图上形成综合图,以更直观的方式反映产生中尺度深厚对流系统发生发展潜势的高低空配置环境场条件。地面分析包括气压、风、温度、湿度、对流天气现象和各类边界线(锋)的分析。国家气象中心的强对流天气预报业务试验表明,中尺度天气的天气图分析已经成为强对流天气潜势预报的重要依据。 相似文献
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中尺度业务预报试验数值模式系统 总被引：8，自引：5，他引：8
以引进的美国Penn State/NCAR中尺度模式（MM2和MM4）为基础，按照实时业务预报需要和我国资料特点，在PC/386微机上研制了中尺度业务预报试验数值模式系统。在1989—1990年进行的实时业务预报试验中，该系统运行稳定，预报时效能满足实时业务预报要求，预报结果对12—24小时短期天气预报具有参考价值，适合于省（市）级气象台站等业务单位使用。 相似文献
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M. W. Moncrieff 《Atmospheric Research》1995,35(2-4)
This essay concerns precipitating convective cloud systems and convectively-driven mesoscale circulations (“mesoscale convection”) and their role in the large-scale structure of the atmosphere. Mesoscale convection is an important and ubiquitous process on scales of motion spanning a few kilometers to many hundreds of kilometers. It plays a role in the input of energy to the climate system through the radiative effect of upper-tropospheric cloud and water vapor, and enhanced surface fluxes. This is in addition to its important effect on energy, heat and momentum transport within the atmosphere. However, mesoscale convection is neither parameterized nor adequately resolved in atmospheric general circulation models. Its representation in mean-flow terms raises issues that are quite distinct from classical approaches to sub-grid scale convection parameterization.Cloud-resolving modeling and theoretical concepts pertinent to the transport properties and mean-flow effects of organized convection are summarized, as are the main convective parameterization techniques used in global models. Two principal themes that are relevant to the representation of organized mesoscale systems are discussed. First, mesoscale transports and their sub-grid scale approximation with emphasis on dynamical approaches. Second, long time-scale modeling of mesoscale cloud systems that involves the collective effect of convection, boundary and surface layers, radiation, microphysics acting under the influence of large-scale forcing.Finally, major research programs that address the role of precipitating convection and mesoscale processes in global models are summarized. 相似文献
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This work analyzes some physical and microphysical properties of Mesoscale Convective Systems (MCSs) and cloud-to-ground lightning. Satellite data from the GOES-10 infrared and NOAA-18 and TRMM microwave channels and lightning information from the Brazilian lightning detection network (BrasilDAT) were utilized for the period from 2007 to 2009. Based on an automatic MCSs detection method, 720 MCSs life cycles were identified during the period and in the region of study, with a lightning detection efficiency of over 90%. During the diurnal cycle, maximum electrical activity occurred close to the time of maximum convective cloud fraction (18 UTC), and 3 h after the maximum normalized area expansion rate. Diurnal cycles of both properties were modulated by diurnal heating, and thus could be used to monitor diurnal variability of lightning occurrence. The electrical activity was more intense for the widest (Pearson’s correlation of 0.96) and deeper (Pearson’s correlation of 0.84) clouds, which reached 390 km size and 17 km maximum cloud top height. Area growth during the initial phase of MCSs exerted a strong influence on their size and duration, and thus also showed a potential for defining the possibility of electrical activity during their life cycle. The average lightning life cycle exhibited a maximum close to MCSs maturation, while the maximum average lightning density occurred in the MCSs initial life cycle stage. The growth rate of electrical activity during the early stages can indicate the strength of convection and the possible duration of systems with lightning occurrence. Strong condensation processes and mass flux during the growth phase of the systems can provide favorable conditions for cloud electrification and lightning occurrence. A comparison of high microwave frequencies with lightning data showed a strong relationship of vertically integrated ice content and particle size with lightning occurrence, with Pearson's correlation of 0.86 and 0.96, respectively. The polarization difference in the 85 GHz channel showed that electrical activity increases linearly with polarization reduction, associated with a high value of Pearson's correlation coefficient (above 0.90). This suggests that regions with more intense electrical activity are predominantly located in areas with a high concentration of larger ice particles that are vertically oriented, due to the existence of intense updrafts and the electric field. These results demonstrate the potential use of thermodynamic, dynamic and microphysical characteristics for analyzing thunderstorms severity, and as additional information for nowcasting and monitoring electrical activity over large regions that lack ground-based lightning sensors. 相似文献
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A review of the understanding and progress in the study of mesoscale cellular convection (MCC) in cloud-topped marine boundary layers is provided. A comparison is made between MCC and the classical study of Benard-Rayleigh convection, with noted similarities and differences. External physical forcing mechanisms in the atmosphere are identified and discussed, in view of their effect on convection development and structure. Onset, horizontal planform, circulation direction, aspect radio and scaling phenomena are explained in terms of atmospheric processes. The global climatology of MCC is also updated and briefly discussed in terms of GCM model development. 相似文献
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Considered are the results of the numerical analysis of two mesoscale cyclonic vortices generated over the Black Sea near the Caucasian coast on August 3, 2007 and August 7, 2010. It is demonstrated for the axially symmetric and more long-lived vortex occurred in 2007 that the Caucasian vortices are two-dimensional structures dying out rapidly due to the turbulent friction in the near-water boundary layer, and the deviation from the strictly two-dimensional motion is associated with the presence of the secondary circulation. The difference is demonstrated in the mechanisms of the origin of vortices in 2007 and 2010. In the first case, this is the formation of cyclonic circulation over the eastern part of the Black Sea limited by the Anatolian and high Caucasian Mountains, at the intrusion of the airflow of northwestern direction. In the second case, these are the processes of the generation of cyclonic vorticity at the baroclinic airflow running around the northwestern edge of the mountain range over the land. 相似文献
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Mesoscale predictability of mei-yu heavy rainfall 总被引：1，自引：0，他引：1
Recently reported results indicate that small amplitude and small scale initial errors grow rapidly and subsequently contaminate short-term deterministic mesoscale forecasts. This rapid error growth is dependent on not only moist convection but also the flow regime. In this study, the mesoscale predictability and error growth of mei-yu heavy rainfall is investigated by simulating a particular precipitation event along the mei-yu front on 4-6 July 2003 in eastern China. Due to the multi-scale character of th... 相似文献
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从数学上分析了Doppler速度（径向速度分量）和水平风场之间的基本关系，利用模拟的Doppler图像讨论了切变线、涡旋和低空急流等各种典型中尺度系统的Doppler速度图像的主要特征。所得结果在短时预报中可用于对实时观测到的Doppler图像作定性解释。 相似文献