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1.
Modes of Mesoscale Convective System Organization During Meiyu Season over the Yangtze River Basin 
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下载免费PDF全文 Mesoscale convective systems （MCSs） are classified and investigated through a statistical analysis of composite radar reflectivity data and station observations during June and July 2010-2012. The number of linear-mode MCSs is slightly larger than the number of nonlinear-mode MCSs. Eight types of linear-mode MCSs are identified： trailing stratiform MCSs （TS）, leading stratiform MCSs （LS）, training line/adjoining stratiform MCSs （TL/AS）, back-building/quasi-stationary MCSs （BB）, parallel stratiform MCSs （PS）, bro- ken line MCSs （BL）, embedded line MCSs （EL）, and long line MCSs （LL）. Six of these types have been identified in previous studies, but EL and LL MCSs are described for the first time by this study. TS, LS, PS, and BL MCSs are all moving systems, while TL/AS, BB, EL, and LL MCSs are quasi-stationary. The average duration of linear-mode MCSs is more than 7 h. TL/AS and TS MCSs typically have the longest durations. Linear-mode MCSs often develop close to the Yangtze River, especially over low-lying areas and river valleys. The diurnal cycle of MCS initiation over the Yangtze River valley contains multiple peaks. The vertical distribution of environmental wind is decomposed into storm-relative perpendicular and parallel wind components. The environmental wind field is a key factor in determining the organizational mode of a linear-mode MCS. 相似文献
2.
湖北三类组织形态强对流系统造成的地面强对流大风特征 总被引：1，自引：0，他引：1
利用湖北省2012~2017年区域自动站、天气雷达和周边探空站观测资料,对三类不同组织形态的中尺度对流系统(Mesoscale Convective System, MCS)(线性MCS、非线性MCS和孤立对流风暴)造成的地面强风(极大风速≥17 m/s)的时空分布、移动与传播、对流环境特征等方面进行了统计对比分析,并结合个例讨论了地面入流大风的成因及其对对流系统发展、组织的影响。结果表明:(1)大量的非线性MCS可能是由更早发生在山区和丘陵的孤立对流风暴向平原地区移动过程中组织形成的,孤立对流风暴造成的地面大风出现的峰值时间在17:00(北京时,下同)前后,非线性MCS地面大风的峰值时间在19:00左右;线性MCS造成的强对流大风主要出现在平原地区。(2)非线性MCS和孤立对流风暴是造成湖北省地面大风的主导系统,其中,非线性MCS造成的地面大风站次数占强对流大风站次总数的41.9%,而39.3%的地面强对流大风站次是由孤立对流风暴造成的。(3)虽然大于17 m/s的地面入流大风占所有强对流大风的比例很小,但存在地面入流大风的强对流系统的影响范围、持续时间均远大于同一类型对流系统的平均值。基于一次长生命史线性MCS(飑线)造成强对流大风事件的分析表明:雷暴系统前侧的地面入流大风是由对流强烈发展造成,这支暖湿入流又进一步增强了对流风暴的发展,同时地面入流大风的形成进一步加强了垂直风切变,因而强的地面入流更有利于对流系统的组织化发展。(4)虽然暖季强对流系统的平均引导气流均以西南风为主,但线性MCS主要自西向东移动、非线性MCS以自西南向东北移动为主、孤立对流风暴的移动方向则更具多样性,也更易出现后向传播现象。孤立对流风暴相对组织化的强对流系统而言,往往发生在更不稳定或更干的层结大气中,且环境垂直风切变更弱、风速更小。 相似文献
3.
在热带气旋的生成过程中,从热带扰动向热带低压增强的过程研究较少,而这一过程必定伴随着中尺度对流系统（MCS）的生成、合并和发展。本文利用FNL分析资料和高分辨率模式对1521号台风“杜鹃”生成前3天进行数值模拟,着重探讨了“杜鹃”生成过程中MCS的发展演变特征。在“杜鹃”生成过程中,对流层上部槽（TUTT）位置偏东,“杜鹃”主要从季风涡旋（MG）的东南侧边缘向西北方向移动,因此,减弱的大尺度垂直风切和MG东南侧的低层辐合都为“杜鹃”的生成提供了有利的动力条件。在“杜鹃”生成前期阶段,新生成更多的MCS有利于在热带扰动阶段“杜鹃”的增强;“杜鹃”生成的中后期阶段,对流爆发,MCS发生合并使得MCS个数减少,MCS结构变得更加紧凑,面积最大的MCS逐渐向热带扰动中心区域收缩,“杜鹃”生成速度加快。对比MCS中的层云降水和对流云降水的特征发现,MCS中层云降水覆盖面积更大;对流云降水的降雨率比层云的降雨率更大,同时变化幅度更明显。层云降水百分比的增加与“杜鹃”增强的过程关系密切,但对流云降水的降雨率增加有利于MCS增强,层云和对流云的共同作用促进了“杜鹃”生成。 相似文献
4.
Convective and stratiform precipitation characteristics in an ensemble of regional climate model simulations 总被引：1，自引：0，他引：1
We apply a recently proposed algorithm for disaggregating observed precipitation data into predominantly convective and stratiform, and evaluate biases in characteristics of parameterized convective (subgrid) and stratiform (large-scale) precipitation in an ensemble of 11 RCM simulations for recent climate in Central Europe. All RCMs have a resolution of 25 km and are driven by the ERA-40 reanalysis. We focus on mean annual cycle, proportion of convective precipitation, dependence on altitude, and extremes. The results show that characteristics of total precipitation are often better simulated than are those of convective and stratiform precipitation evaluated separately. While annual cycles of convective and stratiform precipitation are reproduced reasonably well in most RCMs, some of them consistently and substantially overestimate or underestimate the proportion of convective precipitation throughout the year. Intensity of convective precipitation is underestimated in all RCMs. Dependence on altitude is also simulated better for stratiform and total precipitation than for convective precipitation, for which several RCMs produce unrealistic slopes. Extremes are underestimated for convective precipitation while they tend to be slightly overestimated for stratiform precipitation, thus resulting in a relatively good reproduction of extremes in total precipitation amounts. The results suggest that the examined ensemble of RCMs suffers from substantial deficiencies in reproducing precipitation processes and support previous findings that climate models’ errors in precipitation characteristics are mainly related to deficiencies in the representation of convection. 相似文献
5.
层状云和对流云的雷达识别及在估测雨量中的应用 总被引：10，自引：1，他引：10
参考“峰值法”建立了利用新一代多普勒天气雷达回波强度识别混合型降水过程中层状云和对流云的方法,分析了反射率阈值和影响半径的变化对识别效果的影响,检验了识别效果,并分析该方法在雷达估测降水中的应用。表明本文所建立的暴雨中层状云和对流云识别方法基本合理,配合云的垂直结构分析大部分地区识别的效果较好,同时通过该识别方法对合肥2002年6月19日一次强降水天气过程的估测降水的应用,表明只按层状云的Z-I关系估测的雨强,相对于识别对流云和层状云后分别按各自的Z-I关系估测的单点雨强,其最大差别约达37%,相应的面雨量也有一定的差别;对流云的多少对发展的中尺度对流系统的雨强有很大影响,这次混合型降水过程以对流云降水为主。对流云和层状云是形成暴雨的重要因素,准确地识别两者,对估测降水的精度会有积极作用。 相似文献
6.
利用NCEP FNL分析资料及南京多普勒雷达观测,借助WRF模式,对2017年8月19日发生在长江中下游地区的一次中尺度对流系统(MCS)进行模拟和诊断分析。此次MCS组织模态PS(Parallel Stratiform)型和TS(Trailing Stratiform)型共存,开始为带状结构,最后演变为强弓状飑线。气旋切变和低空急流是此次过程的重要影响系统,而午后强烈发展的地面锋触发了此次强对流。在垂直风切变和冷池共同作用下,西侧初始对流发展为PS型模态,东侧发展为TS型模态。由于PS型模态的中低层垂直风切变发生转向,导致其消散。TS型模态附近冷池和垂直风切变相配合,且在后向入流(Rear Inflow Jets,RIJ)作用下发展成为强弓状飑线;RIJ受中低层涡旋对影响而发展增强,其中气旋式涡旋主要由涡度方程中拉伸项决定,而反气旋式涡旋则主要由倾侧项决定。 相似文献
7.
中国东部暖季对流云与层状云的比例及与降水的对应关系 总被引：2，自引：1，他引：1
基于1985~2011年逐时地面台站观测云资料,分析了对流云和层状云及其比例关系的时空演变特征,结合逐日融合降水资料研究了对流云、层状云与季风雨带的对应关系。结果表明,中国东部暖季（5~9月）对流云发生频率平均为15.4%,层状云为30.0%。对流云与层状云发生频率的比例在广东、广西、海南省东部和贵州省大部分地区大于1,其它地区均小于1。伴随季风雨带的北进南退,层状云发生频率和云量中心均与降水中心对应,且层状云云带与季风雨带位置吻合,随时间的演变趋势也相同,说明季风雨带主要由层状降水构成,对流云发生频率和云量大值中心则位于季风雨带南侧。对流云和层状云发生频率/云量的变化在华南地区和江淮流域呈显著负相关,云的类型主要由大气稳定度决定。对流云和层状云发生频率在华北地区呈显著正相关,水汽是形成云的决定因素。就降水频率而言,华南地区层状云降水和对流云降水各占一定的比例,而江淮流域和华北地区层状云降水频率更大。 相似文献
8.
Cloud is essential in the atmosphere, condensing water vapor and generating strong convective or large-scale persistent precipitation. In this work, the relationships between cloud vertical macro- or microphysical properties, radiative heating rate, and precipitation for convective and stratiform clouds in boreal summer over the Tibetan Plateau (TP) are analyzed and compared with its neighboring land and tropical oceans based on CloudSat/CALIPSO satellite measurements and TRMM precipitation data. The precipitation intensity caused by convective clouds is twofold stronger than that by stratiform clouds. The vertical macrophysics of both cloud types show similar features over the TP, with the region weakening the precipitation intensity and compressing the cloud vertical expansion and variation in cloud top height, but having an uplift effect on the average cloud top height. The vertical microphysics of both cloud types under conditions of no rain over the TP are characterized by lower-level ice water, ice particles with a relatively larger range of sizes, and a relatively lower occurrence of denser ice particles. The features are similar to other regions when precipitation enhances, but convective clouds gather denser and larger ice particles than stratiform clouds over the TP. The atmospheric shortwave (longwave) heating (cooling) rate strengthens with increased precipitation for both cloud types. The longwave cooling layer is thicker when the rainfall rate is less than 100 mm d?1, but the net heating layer is typically compressed for the profiles of both cloud types over the TP. This study provides insights into the associations between clouds and precipitation, and an observational basis for improving the simulation of convective and stratiform clouds over the TP in climate models. 相似文献
9.
运用三维弹性套网格中尺度（b-g）大气模式，对3个强雹暴过程作不同模拟试验，初步探讨了强对流风暴数值模拟及其未来预报的几个基本问题。结果表明:采用单点探空的二维暖云计算能定性预报出某些风暴过程，为强天气警报提供一定的参考信息；对风速风向垂直切变较小的风暴，二维模拟结果与三维模拟较接近；而对具有典型三维结构的超级单体，则用二维模拟或只用单向风分量的三维模拟不能模拟出其基本特征；为对不同风暴的生命、演变和降水发展等进行模式预报，不仅要求采用细致的雹云微物理参数化的三维模式，还要求用能较准确代表风暴发生处的背景 相似文献
10.
基于地面雨滴谱资料分析层状云和对流云降水的特征 总被引：25，自引：7，他引：25
根据由声雨滴谱仪器测量得到的雨滴谱资料,结合降水云的结构来将降水云系划分成为对流云降水云系和层状云降水云系.分析这两种降水云系中的稳定雨滴谱特征,包括雨滴谱的各种特征直径(平均直径Dm、众数直径Dd、平均体积直径Dv、优势直径Dp、中数直径Dna和中数体积直径Dn)、峰值结构和Z-R关系等.通过对这些量的分析,进一步分析划分降水云系的判据. 相似文献
11.
利用星载测雨雷达探测结果对夏季中国南方对流和层云降水气候特征的分析 总被引：10，自引：5，他引：5
本文利用热带测雨卫星(TRMM)上搭载的测雨雷达(PR)十年的探测结果, 对夏季中国南方对流降水和层云降水的气候特征进行了分析。研究结果表明:夏季中国南方层云降水频次较对流降水频次高出两倍以上, 而对流降水强度至少是层云降水强度的4倍; 就整个中国南方而言, 这两种类型的降水对总降水量贡献相当。日变化分析表明夏季中国南方大部分地区的对流降水主要出现在午后, 层云降水出现时间并不集中, 但这两类降水的频次日变化均显示了明显的地域性特征; 对降水廓线日变化的分析结果表明, 对流降水和层云降水廓线的日变化主要表现在“雨顶”高度的日变化, 即对流降水云的厚度有明显的日变化变化特征, 不同地区的降水廓线存在明显的差异。降水率剖面分析结果显示了对流降水的“雨顶” 高度日变化较层云降水剧烈, 降水率的日变化则相反, 且层云降水率的地域性特征更强。 相似文献
12.
山地对流云并合形成积层混合云的过程分析 总被引：6，自引：2，他引：4
本文利用贵阳市气象台2005和2006年5-9月的地面、高空观测和雷达资料等,分析了41次山地对流云并合形成积层混合云的降水过程.研究发现如果分散的多单体对流云若距离较近,则很可能出现大范围地跨接、合并,则有可能形成范围宽广的片状或带状云系,即积层混合云系.云系形成以后在移动的过程中,会将前方不断新生的对流单体合并,从而云系前缘强度增强,云系不断维持.整个系统的生命期往往较分散云团更长,并有可能会形成间歇性或连续性降水.本文分析了山地对流云并合形成积层混合云的一些具体特征. 相似文献
13.
Differences in rainfall budgets between convective and stratiform regions of a torrential rainfall event were investigated using high-resolution simulation data produced by the Weather Research and Forecasting(WRF) model. The convective and stratiform regions were reasonably separated by the radar-based convective–stratiform partitioning method, and the threedimensional WRF-based precipitation equation combining water vapor and hydrometeor budgets was further used to analyze the rainfall budgets. The results showed that the magnitude of precipitation budget processes in the convective region was one order larger than that in the stratiform region. In convective/stratiform updraft regions, precipitation was mainly from the contribution of moisture-related processes, with a small negative contribution from cloud-related processes. In convective/stratiform downdraft regions, cloud-related processes played positive roles in precipitation, while moisture-related processes made a negative contribution. Moisture flux convergence played a dominant role in the moisture-related processes in convective or stratiform updraft regions, which was closely related to large-scale dynamics. Differences in cloud-related processes between convective and stratiform regions were more complex compared with those in moisture-related processes.Both liquid-and ice-phase microphysical processes were strong in convective/stratiform updraft regions, and ice-phase processes were dominant in convective/stratiform downdraft regions. There was strong net latent heating within almost the whole troposphere in updraft regions, especially in the convective updraft region, while the net latent heating(cooling) mainly existed above(below) the zero-layer in convective/stratiform downdraft regions. 相似文献
14.
Convective and Stratiform Cloud Rainfall Estimation from Geostationary Satellite Data 总被引：6，自引：0，他引：6
The Bayes Decision (BD) method was used to distinguish the corrective and stratiform components of cloud sys-tems from GMS-4 satellite data. A technique originally developed by Adler and Negri (1988, hereafter abbreviated AN) was improved for estimating the convective and stratiform cloud precipitation areas and rates of cloud systems from GMS satellite imagery. It has been applied to a tropical cyclonic cloud cluster observed over east coast area of China on September 23, 1992, which brought about flood disaster in that region. Overlaid 6-hour surface rainfall ob-servations show that the rainfall areas and amounts match with results from improved AN technique. The successful application of the Adler and Negri’s technique to convective and stratiform clouds provides encouragement for the use of this method over large region of mid-latitude China where radar data are not fully covered. 相似文献
15.
16.
用多种加密观测资料和NCEP日再分析资料分析了2010年7月14日强降水期间咸宁地区一次非线状MCS活动造成短时强降水的发生发展机制.结果表明,14日13-18时非线状MCS回波结构组织性差,强对流单体散乱地分布在大片层状回波中,准静止地维持在湖北咸宁地区大约5h,造成了短时强降水.该MCS发生在梅雨锋锋面附近的地面涡旋环流中,高空冷空气侵入和锋前抬升运动是对流的主要触发机制,切变线南侧不稳定的暖湿气流在长江中游地区辐合集中、局地的地面气流辐合和边界层有利的风切变是该非线状MCS发展维持在成宁地区的有利条件.高时空分辨率探测资料对MCS演变过程有较好的分析能力. 相似文献
17.
为认知降水云内的大气温湿结构特点,本文利用1998至2012年热带测雨卫星的测雨雷达(TRMM PR)和全球探空数据集(IGRA)的探测结果,融合计算获得了一套大气温湿廓线和降水廓线的准时空同步资料,并利用该融合资料研究了雨季东亚和南亚降水云内的温湿结构和不稳定能量特点。个例研究结果表明深厚对流降水表现出整层大气湿润、高空风速小的特点,层云降水则表现出850 hPa以下大气湿润、水汽随高度升高显著减少、高空风速大的特点。统计结果表明东亚季风区降水强度更大,对流和层云降水的回波顶高度分别可达17 km和12 km;南亚季风区降水强度较弱,回波顶高度比东亚约低1 km;统计结果还表明南亚季风区对流活动受季风推进的影响显著。两个季风区降水云团内的温度结构差异主要出现在近地面,南亚的近地面温度比东亚约高4℃,南亚对流降水云内的大气较东亚更干燥;整个雨季南亚降水的对流有效位能(CAPE)要大于东亚。本研究结果为模式模拟降水云温湿结构提供了观测依据。 相似文献
18.
Abstract Triangulation from paired sferics (100 ± 50 kHz) received at stations 57 km apart gave 42 map locations of lightning flashes belonging to a thunderstorm well‐defined on weather radar. This storm was one of many in a long line along the leading edge of a band of light stratiform precipitation (snow above 3 km). The band was 9 km high and 60 km wide, and the storms were embedded in it. The convective region of the storm studied had a north‐south extent of 20 km, the east‐west extent averaging two‐thirds as much. Cumulus heights progressed from 3 km on the west to 7 ± 1 km on the east. Two‐thirds of the lightning flashes were in the convective region. The remaining third were in 160 km2 of the light stratiform precipitation immediately west of it. 相似文献
19.
Severe weather reports and composite radar reflectivity data from 2010–14 over North China were used to analyze the distribution of severe convective wind(SCW) events and their organizational modes of radar reflectivity. The six organizational modes for SCW events(and their proportions) were cluster cells(35.4%), squall lines(18.4%), nonlinear-shaped systems(17.8%), broken lines(11.6%), individual cells(1.2%), and bow echoes(0.5%). The peak month for both squall lines and broken lines was June, whereas it was July for the other four modes. The highest numbers of SCW events were over the mountains, which were generally associated with disorganized systems of cluster cells. In contrast, SCW associated with linear systems occurred mainly over the plains, where stations recorded an average of less than one SCW event per year. Regions with a high frequency of SCW associated with nonlinear-shaped systems also experienced many SCW events associated with squall lines. Values of convective available potential energy, precipitable water, 0–3-km shear, and 0–6-km shear, were demonstrably larger over the plains than over the mountains, which had an evident effect on the organizational modes of SCW events. Therefore, topography may be an important factor in the organizational modes for SCW events over North China. 相似文献
20.
2014年5月22日华南地区出现了一次大范围强对流天气过程,该过程中出现了两个中尺度对流系统(Mesoscale Convective System,MCS)MCS-A和MCS-B,两个MCS表现出迥异的形态特征,产生了不同的强对流天气。利用多源观测资料以及高分辨率数值模式分析了环境条件对于MCS形态特征的影响,结果表明:(1)广西夜间到凌晨边界层顶附近强盛的低空急流,使得MCS-A在北部山区出现后向建立(BB, back building)的形态特征,有利于大量级的短时强降水的出现;(2) MCS-A进入广西平原地区以后,强盛的边界层以上的低空急流使得能量垂直廓线的极大值在边界层高度以上,且风垂直切变特征不利于冷池前方的垂直运动发展,冷池前方无法连续触发对流,MCS-A逐渐演化成线状对流/层云伴随(TL/AS, Training Line/Adjoining stratiform)的形态特征,而后消亡;(3)在广东,能量极大值出现在大气底层,环境风廓线有利于冷池前方垂直运动发展,进而触发新的对流,新生成的MCS-B呈现典型的层云拖曳型(TS,trailing stratiform)形态,最终形成飑线,造成雷暴大风天气。 相似文献