共查询到20条相似文献，搜索用时 15 毫秒
1.
2.
本文在十一层原始方程模式中引入Fritsch-Chappell一维云模式，对1982年5月12日江淮气旋上中尺度系统进行了模拟试验，分析表明:Fritsch-Chappell一维云模式对深厚积云的考虑细致合理，比郭晓岚积云参数化方案优越，它能模拟出中尺度系统的一些特征。通过数值计算发现:中尺度江淮气旋是对流层低层的天气系统，气压场上具有中尺度低压的某些特征；对流天气的出现，使得中尺度江淮气旋得到发展，但这种发展有一个变化过程，在对流发展加强时，对流引起的动量变化以及下沉气流造成的低层冷却作用，使其有一个暂时的减弱过程，当对流运动趋于减弱时，气旋才得以发展。 相似文献
3.
采用中尺度WRF模式（WRF3．4）和WRF-3DVAR系统,同化GTS常规观测资料和GPS反演的探空廓线资料,对2012年8月10日发生在江苏东北部地区的一次突发性特大暴雨进行数值模拟,并利用高分辨率的模式输出数据对此次暴雨过程进行多尺度分析和对流不稳定性研究。结果表明：模拟结果较好地再现了此次过程;台风低压和中纬度槽脊系统相互作用,中低层弱冷空气扩散和高、低空急流耦合为此次暴雨过程提供了有利的大尺度背景;地面中尺度辐合线和迅速发展的β中尺度对流系统（M8CS）是直接导致此次局地突发性暴雨的中尺度系统,地面中尺度辐合线的位置和暴雨的落区基本一致,M8CS的强烈发展对应于暴雨的最强阶段;暴雨发生前和暴雨发生时,对流系统中等日。线密集而陡峭,不稳定能量的突然性释放造成αθ／Oz迅速减小,口。垂直剖面呈伸向低空的“漏斗状”分布,有利于垂直涡度和对流不稳定发展。 相似文献
4.
局地强对流系统发展多样性的个例研究 总被引：2，自引：1，他引：1
在北京"7.18"强降水天气过程中,中尺度对流系统的启动、发展方式较为复杂,造成对流系统发展多样性特征的机制也存在差别。天气尺度动力条件和局地层结不稳定结构都表明,此次局地强天气的发生有良好的环境条件。通过高分辨率中尺度观测的分析表明,怀柔—密云地区存在孤立发展的对流系统,最终发展为多单体雷暴群;而在北京西南部线状对流的不连续传播发展特征十分显著。数值模拟结果表明,地面中尺度切变线的活动对北京东北部怀柔—密云地区对流系统的启动起了关键作用;在环境场与对流的相互作用机制下,北京西南部的中尺度对流系统的发展传播与重力波活动有密切关系。对流系统的表现形式和发展演变的多样性特征,体现了起支配作用的物理机制的差异。 相似文献
5.
登陆台风内中尺度强对流系统演变机制的湿位涡分析 总被引：1，自引：0，他引：1
2005年05号台风"海棠"登陆福建后,在外围云系里有个明显发展的中尺度对流云团经过温州东部及北部地区,引起了强降水,从而造成比热带风暴环流本身更具破坏力的强烈天气,因此研究台风内中尺度对流系统(M(2S)的发展机制能够为预报台风灾害提供依据.文中使用中尺度静力模式WRF对台风"海棠"登陆过程进行了模拟,模式很好地模拟了台风登陆过程的路径、强度变化趋势和降水分布,尤其是模拟出了台风环流内的一次中尺度对流系统的发展过程,并利用模拟结果对台风环流内的这次中尺度对流系统进行了与之相关联的湿位涡分析,从而揭示了台风环流内中尺度对流系统发展演变的湿位涡特征.结果表明,在对流形成阶段,MPV1即对流不稳定为MCS的形成提供背景不稳定条件,由MPV2即湿等熵面的倾斜和水平风的垂直切变而引起的涡旋发展作为强迫机制:MCS形成的区域及东南区域中低层是强对流不稳定层,蕴含丰富的不稳定能量,倾斜上升运动把对流不稳定区具有强不稳定能量的暖湿卒气向西北中层的中性层结区输送.由于θep的减小,气旋性涡度增强,有利于形成对流,另一方面,由于湿等熵面倾斜和低空急流加强而引起的涡旋发展作为一种强迫机制激发对流不稳定能晕得到释放,从而形成对流;在对流系统的发展阶段,由于低层的对流不稳定性进一步减弱,θep一步减小,气旋性涡度进一步增强,有利于MCS的增强,中层等θe线的倾斜度比绝对动量M等值线的倾斜度大,对应有条件对称不稳定区域,满足条件对称不稳定(CSI)条件,在湿等熵面倾斜和台风低空急流作用下引起的涡旋发展强迫对称不稳定能量释放,从而使得对流得以维持和加强.通过以上的分析给出了台风环流内中尺度对流系统发生发展的概念模型. 相似文献
6.
The role of the convective “trigger function” in numerical forecasts of mesoscale convective systems 总被引：1，自引：0，他引：1
Summary Three-dimensional numerical model simulations of a mesoscale convective system are performed to evaluate the sensitivity of the simulations to differences in the convective trigger function. The Penn State/NCAR mesoscale model with the Kain-Fritsch convective parameterization scheme is used as the modeling system for the study. All simulations are performed on the June 10–11, 1985 squall line from the OK PRE-STORM field experiment. Individual simulations differ only in their specification of the trigger function within the Kain-Fritsch scheme. Comparison of results from 12 hour simulations indicates that the position, timing, and intensity of convective activity and mesoscale features vary substantially as a function of the trigger function formulation. The results suggest that the convective trigger function is an integral part of the overall convective parameterization problem, and that great care must be exercised is designing realistic trigger function formulations, especially as model resolutions approach the scale of individual convective clouds.With 7 Figures 相似文献
7.
Simulations of a mesoscale convective system (MCS), which propagated across Northern India on 2nd May 2018 - leading to many fatalities when the gust front knocked down homes and tore apart building roofs - have been performed using the National Centre for Medium Range Weather Forecasting (NCMRWF) Unified Model – Regional (4 km horizontal grid spacing), to evaluate the model’s convective treatments. Though the model captures many of the qualitative and quantitative features, it slightly lags behind the observed MCS organisation and movement, produces lesser precipitation, and lacks the spatial separation between two adjacent organised convective systems in the satellite observations – leading to a faintly offset MCS track. Sensitivity simulations are then performed, for this non-equilibrium MCS case, with different partitioning between parametrized and explicit convection to assess the reliance of the convective treatments on the large-scale environment, as well as to test the notion of a breakdown of convective parametrization at the mesoscale model resolution. Fully parametrized (FP) convection produces even lesser rainfall and are dominated by orographic precipitations along the foot hills of Himalayas with no any trace of the MCS. Fully explicit (FE) convection realistically simulates most of the prominent convective cells and enhance precipitation along the MCS track that agree better with the observations, though the ‘two lobes’ of intense precipitation are not resolved; instead it produces a squall line of precipitation. The FE configuration generates the most vigorous convective updraft, along with a vertical shear that is tilted westward. The simulation with partially parametrized and partially explicit convection resembles the fashion in the FP and FE scenarios, with a transition over the duration of the run from parametrized to explicit precipitation. The results are in line with the notion from previous studies; that the majority of successful explicit simulations of mesoscale organisation are those associated with strong large-scale forcing for convection, wherein resolved vertical motions are sufficient to minimise delays in onset. 相似文献
8.
Numerical Simulation of Torrential Rainfall and Vortical Hot Towers in a Midlatitude Mesoscale Convective System 
下载免费PDF全文
下载免费PDF全文 A cloud-resolving model simulation of a mesoscale convective system （MCS） producing torrential rainfall is performed with the finest horizontal resolution of 444 m. It is shown that the model reproduces the observed MCS, including its rainfall distribution and amounts, as well as the timing and location of leading rainbands and trailing stratiform clouds. Results show that discrete convective hot towers, shown in Vis5D at a scale of 2-5 kin, are triggered by evaporatively driven cold outflows converging with the high-θe air ahead. Then, they move rearward, with respect to the leading rainbands, to form stratiform clouds. These convective towers generate vortical tubes of opposite signs, with more intense cyclonic vorticity occurring in the leading convergence zone. The results appear to have important implications for the improvement of summertime quantitative precipitation forecasts and the understanding of vortical hot towers, as well midlevel mesoscale convective vortices. 相似文献
9.
The Advanced Research WRF（Weather Research and Forecasting） model is used to simulate the evolution of a mesoscale convective vortex（MCV） that formed on the Meiyu front and lasted for more than two days. The simulation is used to investigate the underlying reasons for the genesis, intensification, and vertical expansion of the MCV. This MCV is of a type of mid-level MCV that often develops in the stratiform regions of mesoscale convective systems. The vortex strengthened and reached its maximum intensity and vertical extent（from the surface to upper levels） when secondary organized convection developed within the mid-level circulation. The factors controling the evolution of the kinetic and thermal structure of the MCV are examined through an analysis of the budgets of vorticity, temperature, and energy. The evolution of the local Rossby radius of deformation reveals the interrelated nature of the MCV and its parent mesoscale convective system. 相似文献
10.
强热带风暴碧利斯 (0604) 引发的特大暴雨中尺度结构多普勒雷达资料分析 总被引：11，自引：3，他引：8
强热带风暴 “碧利斯” (Bilis) 于2006年7月14日12:50在福建省霞浦县北壁镇再次登陆, 与南海季风相互作用, 在福建省引发特大暴雨。作者利用双多普勒雷达三维风场反演技术对厦门和龙岩新一代多普勒雷达时间同步探测资料进行了风场反演, 综合利用雷达回波强度资料, 对造成长泰、 漳州特大暴雨的中尺度对流系统的三维结构及其演变特征进行了详细分析。结果表明: (1) 此次特大暴雨主要是由中低层西南[CD*2]东北走向的β中尺度辐合线引发的, 辐合线对于水汽输送以及暴雨的形成、 触发、 维持具有重要作用, 辐合线在暴雨的整个生命史过程中经历了由弱变强、 由强变弱的演变过程, 变化过程与降水的强弱演变过程基本同步。 (2) 由于丰富的水汽供应和中低层辐合线的动力抬升作用, 西南[CD*2]东北走向的β中尺度回波带的西南不断有新的γ中尺度对流单体生成, 在沿着辐合线向东北移动过程中进一步发展、 合并形成β中尺度对流线, 造成持续的强降水。最后, 还给出了此次特大暴雨的三维云系结构模型。 相似文献
11.
12.
阵风锋过程一般伴随中尺度强对流系统发生, 在近地层形成很大的阵风及风切变, 容易造成风灾, 特别是对航空部门有很大的影响。本文对2006年6月29日发生在南京的一次由强中尺度对流系统引发的阵风锋过程进行分析, 通过多普勒天气雷达资料以及地面中尺度观测网观测到的实况, 可以清楚地看出这个阵风锋系统的结构。当阵风锋经过时, 地面测站观测到明显的风向变化、 风速增大、 气压增强、 温度下降, 而后出现强降水等特点, 这些都符合阵风锋的结构特征。利用地面测站实时观测到的气压、 相对湿度、 温度等计算得到折射指数, 它在阵风锋刚经过时迅速增大, 而后随阵风锋外移逐渐减小, 但是因为阵风锋后对流系统的影响, 折射指数还要维持很长时间的高值。从雷达观测的反射率强度上能看到阵风锋位置的回波强度、 高度都比两侧要大, 与后方强对流系统之间的距离有5～10 km。对雷达观测到的径向速度进行反演, 可看到上层的速度大于近地层速度, 并且强速度中心靠前, 在近地层形成向后的气流(回流)。阵风锋在多普勒速度场中表现出明显的线状组合切变, 利用阵风锋的这个特点设计自动识别算法, 能够有效地对阵风锋进行识别, 组合切变也能有效地对阵风锋的发展以及移动作预报。 相似文献
13.
利用自动站观测资料、FY-2G卫星资料和多普勒雷达等资料,对发生在副热带高压影响下的重庆局地强风暴过程进行了观测和数值模拟分析,探讨了其中尺度对流系统(MCS)演变,抬升触发和维持机制。结果表明:(1)在副热带高压影响下,重庆处于高温、高湿气团中,大气层结极不稳定;(2)此次局地风暴抬升触发的关键因子是地面附近浅薄边界层中尺度辐合线,辐合线由川渝盆地中西部MCS的雷暴高压与重庆地面热低压共同作用形成;(3)中尺度辐合线触发的对流风暴形成小范围冷池出流与环境风场形成新的辐合线,加强对流风暴发展,并再次触发新的对流单体。承载层平均风为偏南风,使得对流单体向北缓慢移动,冷池出流和边界层辐合线共同作用使得风暴单体向西向北传播和长时间维持。 相似文献
14.
2001年8月初上海强暴雨中尺度对流系统的数值模拟研究 总被引：10，自引：2，他引：10
利用NCEP的ETA模式对 2 0 0 1年 8月 5～ 6日导致上海地区产生大暴雨的中尺度对流系统的发生发展过程进行了数值模拟。模拟结果基本再现了对流云团加强合并形成中尺度对流系统的过程 ,所模拟的降水分布、最大降水中心位置与实测结果基本一致。模拟结果还显示其中的一个中尺度对流系统是由于位于其西南部的一支低空急流的直接流入才发展起来的 相似文献
15.
黔西南一次中尺度暴雨的数值模拟诊断研究 总被引：6，自引：0，他引：6
使用WRF模式 (Weather Research and Forecasting model) 模拟了2006年6月12日贵州省西南部一次典型的突发性强对流暴雨过程, 模式较真实地模拟了这次局地发展的中尺度暴雨天气过程。对流层低层的中尺度辐合线造成了初始的上升运动, β中尺度对流系统首先在地面锋线前不稳定的暖区中生长, 辐合线南侧的偏南气流对水汽和热量的输送是对流能够持续生长的最重要因素。通过非地转ω方程的诊断证明, 在降水开始后, 凝结加热的释放对β中尺度对流系统的发展最为重要, 它强迫产生的上升运动分量超过了低层暖平流强迫造成的上升运动分量。在相应的热力、 动力结构的调整作用下, 对流层低层出现中尺度低空急流、 中尺度涡旋等动力结构。到降水过程后期, 由于偏北气流的侵入, 降水区上空对流层低层转为对流稳定的层结, β中尺度对流系统无法获得不稳定能量以维持其发展, 降水也逐渐减弱直至终止。 相似文献
16.
《Atmospheric Research》2010,95(4):715-725
Flash floods are associated with highly localized convective storms producing heavy rainfall. Quantitative precipitation forecasting of such storms will potentially benefit from explicit representations of deep moist convection in numerical weather prediction models. However, explicit representation of moist convection is still not viable in operational mesoscale models, which rely on convective parameterizations for issuing short to medium-range forecasts. In this study we evaluate a technique that uses regional Cloud-to-Ground (CG) lightning observations to define areas of deep moist convection in thunderstorms and adjust the model-generated precipitation fields in those regions. The study focuses on a major flash flood inducing storm in central Europe (23 August 2005) that was simulated with the aid of an operational weather forecasting system (POSEIDON system based on Eta/NCEP model). The performance of the technique is assessed using as reference distributed rainfall estimates from a network of radar observations. The results indicate that CG lightning data can offer sufficient information to increase the mesoscale model skill in reproducing local convective precipitation that leads to flash floods. The model error correction is shown to be proportional to the density of lightning occurrence, making the technique potentially suitable for operational forecasting of flash flood inducing thunderstorms. 相似文献
17.
18.
The conventional and intensive observational data of the China Heavy Rain Experiment and Study (CHeRES) are used to specially analyze the heavy rainfall process in the mei-yu front that occurred during 20-21 June 2002, focusing on the meso-β system. A mesoscale convective system (MCS) formed in the warm-moist southwesterly to the south of the shear line over the Dabie Mountains and over the gorge between the Dabie and Jiuhua Mountains. The mei-yu front and shear line provide a favorable synoptic condition for the development of convection. The GPS observation indicates that the precipitable water increased obviously about 2 3 h earlier than the occurrence of rainfall and decreased after that. The abundant moisture transportation by southwesterly wind was favorable to the maintenance of convective instability and the accumulation of convective available potential energy (CAPE). Radar detection reveals that meso-β and -γ systems were very active in the Mα CS. Several convection lines developed during the evolution of the MαCS, and these are associated with surface convergence lines. The boundary outflow of the convection line may have triggered another convection line. The convection line moved with the mesoscale surface convergence line, but the convective cells embedded in the convergence line propagated along the line. On the basis of the analyses of the intensive observation data, a multi-scale conceptual model of heavy rainfall in the mei-yu front for this particular case is proposed. 相似文献
19.
利用原始方程模式讨论了不同大气层结对冷锋环流的影响及其在激发锋区中尺度强对流系统中的作用，结果表明：层结对锋区环流有非常大的影响，随层结稳定度的减小，锋区非地转越锋环流和上升运动迅速增强，锋前暖区有可能产生中尺度强对流和多重中尺度上升运动带，并有利于对称不稳定的激发；层结对冷锋环流的影响和锋区中尺度强对流系统形成的作用主要由中低层的大气层结状态决定 相似文献