登陆台风Matsa (麦莎) 中尺度扰动特征分析

地面中尺度自动站和多普勒雷达资料的分析都表明, 台风Matsa登陆后的低层螺旋云带中活跃着中尺度气旋性涡旋系统。本文使用新一代中尺度WRF模式对台风Matsa登陆后的变化特征进行了数值模拟, 使用四维变分多普勒雷达分析系统 (4D-VDRAS) 对台风Matsa多普勒雷达径向风进行了风场反演。在此基础上对台风Matsa登陆后中尺度扰动特性进行了初步探讨; 对台风Matsa与其螺旋云带的中尺度系统之间动能和涡度的相互转换进行了诊断分析。分析表明: (1) 数值模拟和雷达风场反演结果表明, 登陆台风Matsa的低层螺旋云带中活跃着中尺度气旋式涡旋系统, 与之相伴随的为较强的中尺度上升区, 而且, 中尺度垂直上升运动的强弱与雷达对流回波强度成正相关, 中尺度垂直上升运动越强, 雷达对流回波发展越旺盛。 (2) 台风Matsa与其中尺度系统动能转换的诊断分析说明, 低层中尺度系统从台风Matsa环流中获得动能而发展; Matsa在陆地上长久维持主要是从高层获得动能。 (3) 台风Matsa与其中尺度系统涡度转换的诊断分析说明, 低层中尺度系统向Matsa输送正涡度主要依靠中尺度垂直运动来完成; 高层正涡度的转换通过水平输送和垂直输送共同来完成。所以, 中尺度系统所产生的正涡度源源不断地向Matsa输送, 使Matsa的气旋性环流可以在陆地上长久维持。     

登陆台风维持和暴雨增幅实例的能量学分析

对登陆后迅速消亡的８１１６号台风和登陆后长期维持不消的８４０７号台风的动能平衡作对比分析，结果表明：对流层上部动能水平通量辐散和穿越等压线的运动使８１１６号台风迅速消亡，其中以正压过程为主；８４０７号台风则从环境大气输入动能和位能，这可能是台风暖性低压长久不消的重要原因。最后讨论了台风动能水平通量辐散与外围暴雨增幅的关系。     

登陆台风动能平衡和转换的诊断

对一次登陆台风及其外围暴雨和环境的动能平衡以及天气尺度动能与中尺度扰动动能的转换进行了诊断分析，指出摩擦消耗和动能的水平输出是台风的主要能汇。台风消亡期间，外围暴雨区动能增大，动能制造项Ｇｋ是暴雨区的主要能源。Ｇｋ的增大可能与天气尺度动能转换成中尺度扰动引起暴雨的发展相联系。     

登陆台风研究概述

国际热带气旋研究界自20世纪90年代以来，把台风登陆从传统的台风路径体系中分离出来，成为国际台风研究的重点，例如WMO的世界天气研究计划(WWRP)、美国的天气研究计划(USWRP)和澳大利亚的某些研究项目都把台风登陆作为重点课题投入研究。陈联寿在全国第11届热带气旋科学讨论会上，提出了台风登陆的PDP计划，指出台风登陆阶段是研究台风、海洋、地形(岛屿、海岸、浅海区大陆架)3者相互作用的唯一手段。也是考察预报警报、社会响应和风暴灾害3者相互影响的良机。登陆台风引起的暴雨、台风大风、风暴潮等都有很大的变化。因此，把登陆作为一个独立的问题来研究十分必要。目前，对登陆台风研究也有不少成果，笔者从登陆台风的气候特征、陆地路径、强度变化以及登陆台风暴雨等方面作一简要的概述。     

台风蒲公英两次登陆过程的强度变化分析

主要通过台风蒲公英来研究台风登陆时的强度变化问题。首先利用雷达回波资料分析了台风蒲公英在台湾和浙江两次登陆过程的结构变化,发现第一次登陆后,结构明显变得松散,第二次登陆后,气旋的结构反而变得更有组织性、更紧密。并用浙江省地面自动气象站资料来分析雨带分布、地面涡度分布的变化情况,进一步证实“蒲公英”在浙江登陆后强度确实有所加强。最后用NCEPT再分析资料对比分析了“蒲公英”在两次登陆时的水汽和斜压能量等条件,发现第二次登陆时环境条件明显要好。因此认为台风蒲公英在浙江登陆后强度维持的原因主要是水汽的输送,北面冷空气的入侵等。     

登陆台风及其暴雨的研究进展

登陆台风及其暴雨的研究取得的进展主要包括登陆台风的结构和强度变化、路径突变、变性过程及其暴雨和大风。     

环境风垂直切变与登陆台风强度变化关系的统计分析

为了了解环境风垂直切变在登陆台风强度突变下所起的作用,利用1990-2004年登陆中国的111个台风的强度、登陆位置以及NCEP/NCAR每日4次等压面风场等资料,分析了风速垂直切变对台风登陆过程中强度变化的影响.结果表明,与海盆中相比,环境风垂直切变与登陆台风强度的线性相关性减小,滞后的时间长度减短;环境风垂直切变与滞后6～18 h的台风强度有不可忽视的相关性,与滞后6 h的台风强度相关最佳,相关系数为0.215;对于显著增强的登陆台风,其所处的环境风垂直切变不太大,平均在9 m·s-1以下,反之当环境风垂直切变在9 m·s-1以上时,登陆台风的强度也有可能显著减弱;与在华南登陆的台风相比,在华东登陆的台风其减弱型样本相对更多,其强度受风速垂直切变影响衰减得更快.     

0601号登陆台风及暴雨减弱消亡过程中的动能收支分析

利用高分辨率（10km）数值模拟的结果,以登陆华南并引发特大暴雨的0601号台风为例,对台风中田尺度动能收支平衡进行了诊断分析。结果表明,中-β尺度系统动能收支水平项（水平通量散度项和水平产生项）很小,垂直项（垂直通量散度项和垂直产生项）是动能收支方程的主要部分;动能垂直通量散度在对流层低层是动能的汇,在对流层中高层为动能的源;动能垂直产生项在对流层各层都是动能的汇;浮力产生项在300hPa以下是动能的源,在对流层高层是动能的汇;平均动能的局地变化项,在对流层各层均小于零,暴雨期间对流层动能支大于收,且动能变化在对流层中低层最明显。就整个对流层的垂直总量而言,浮力产生项是主要的动能源,而垂直产生项是主要的动能汇。较强冷空气首先从对流层中层入侵台风环流系统,抑制动能制造和传输,是中田尺度对流系统不能维持、发展的主要原因,也是台风系统及其暴雨不能长久维持的关键。     

台风登陆前后异常变化的研究进展

国家重点基础研究发展计划（973计划）项目——“台风登陆前后异常变化及机理研究”经过5年（2009—2013年）的研究完成研究任务。项目系统性地开展了16个台风的外场观测试验,在浅水区的海气拖曳系数、边界层高度变化等方面获得新的观测结果;发展了针对登陆台风的多源资料融合方法,例如台风雷达风场反演和同化技术取得进展;揭示了不同尺度系统活动导致台风路径突变、登陆台风复苏、双眼壁的形成等的物理机制;改进了涡旋初始化和积云对流参数化技术,提出了新的云辐射参数化方案,建立了台风海-陆-气耦合模式,台风数值预报关键技术的研发取得明显进展,文中介绍该项目所取得的代表性成果,对台风登陆前后异常变化的科学问题及研究进展进行综述。     

登陆台风近地层湍流特征观测分析

在对多个登陆台风实地观测的基础上,选取出较有代表性的实验观测个例:“黄蜂”、“杜鹃”和“黑格比”3个登陆台风,分析探讨在登陆台风的中心、靠近中心位置的强烈影响区域和台风外围环流影响地区近地层湍流特征,以期对登陆台风的边界层湍流过程有所认识。观测资料分析显示,在登陆台风的中心及其强烈影响的区域:(1)风速和湍流强度均有强烈的变化;(2)水平湍流积分尺度明显增大,越靠近中心位置,增大越明显,而垂直方向没有明显变化;(3)在湍流谱的低频和高频区,湍能均可增大1~2个量级,其中垂直方向湍能增大的幅度略小于水平方向;(4)湍谱在惯性子区u,v,w3个方向的分布均不满足-5/3次方律,存在较大偏移,而在台风外围环流影响区和无台风影响时,则无上述的4个特征。     

湿地边界层通量影响热带气旋登陆维持和降水的数值试验

用MM5v3模式及其TC Bogus方案对台风Nina(7503)在中国大陆上的维持加强过程进行模拟,并通过各种敏感性试验,研究了饱和湿地对热带气旋在大陆上维持和降水的影响。结果表明:湿地边界层内各通量对登陆热带气旋的强度、结构及其降水具有明显影响。潜热通量和感热通量均有利于热带气旋的维持和加强,其中潜热输送的作用显著,感热输送的作用较小。潜热和感热通量有利于热带气旋雨带螺旋结构的维持,对台风降水分布有明显影响,动量通量对热带气旋风场有显著的削弱作用,是其能量耗散、低压填塞的主要原因,但对台风降水具有局地增幅作用。     

TERRAIN IMPACT ON THE PRECIPITATION OF LANDFALLING TYPHOON TALIM

The impact of terrains on the precipitation of landfalling typhoon Talim (2005) over mainland China is investigated using the fifth-generation Pennsylvania State University-National Center for Atmospheric Research Mesoscale Model. The simulated precipitation of simulated typhoon (the control) matches the observations closely. To compare with the control simulation, four sensitivity simulations were carried out in which terrains of Wuyi Mountain, Lushan, Dabieshan, and both Lushan and Dabieshan are completely removed respectively, but other surface properties were retained. It is found that the complex terrains of Wuyi Mountain, Lushan and Dabieshan have a significant impact on the rainfall intensity and distribution of Talim. As the terrains are removed, the rainfall is decreased very greatly and the rainfall in inland area is decreased much more than that in the coastal area. Besides, the rainfall distribution near the Lushan and Dabieshan is spread much more westward compared with the control simulation. Further analysis shows that the Wuyi Mountain would increase both the lower level air convergence and the upper level air divergence for Talim that just made landfall and thus it would contribute to the convection and increase rainfall intensity. It can be concluded that the terrains of Wuyi Mountain, Lushan and Dabieshan have obvious impacts on the Talim rainfall, and their impacts are different in various landfalling periods. The present study is a useful attempt to explore the influence of orography on the TCs in mainland China.     

NUMERICAL SIMULATION STUDY ON THE RAPID INTENSIFICATION OF TYPHOON HAIKUI (1211) OFF THE SHORE OF CHINA

Forecasting the rapid intensification of tropical cyclones over offshore areas remains difficult. In this article, the Weather Research and Forecast (WRF) model was used to study the rapid intensification of Typhoon Haikui (1211) off the shore of China. After successful simulation of the intensity change and track of the typhoon, the model output was further analyzed to determine the mechanism of the rapid change in intensity. The results indicated that a remarkable increase in low-level moisture transportation toward the inner core, favorable large-scale background field with low-level convergence, and high-level divergence played key roles in the rapid intensification of Typhoon Haikui in which high-level divergence could be used as an indicator for the rapid intensity change of Typhoon Haikui approximately 6 h in advance. An analysis of the typhoon structure revealed that Typhoon Haikui was structurally symmetric during the rapid intensification and the range of the eyewall was small in the low level but extended outward in the high level. In addition, the vertically ascending motion, the radial and tangential along wind speeds increased with increasing typhoon intensity, especially during the process of rapid intensification. Furthermore, the intensity of the warm core of the typhoon increased during the intensification process with the warm core extending outward and toward the lower layer. All of the above structural changes contributed to the maintenance and development of typhoon intensity.     

8807号登陆台风的数值研究：内核结构及能量水汽收支

使用PSU/NCAR研制的非静力中尺度模式MM5对登陆后维持较久的典型个例8807号台风(Bill)进行了数值模拟。模拟采用了网格距分别为18和6 km的两重双向嵌套网格。通过给定初始涡旋和选择合适的物理过程,模式不仅比较好地模拟了Bill的强度变化过程,而且再现了风暴的移动轨迹,对降水量的模拟也相当成功。文中利用细网格的模拟结果,分析台风登陆前后的内核结构特征和能量水汽收支,揭示Bill登陆后维持较久的可能原因。分析表明,Bill台风登陆后出现了中低层的稳定度特别是湿稳定度显著加大、表面热通量和水汽通量明显减小、摩擦耗散的动能显著增加等不利于台风维持的特征。但是台风登陆后眼墙结构长时间维持,在登陆初欺眼墙区的上升气流乃至较登陆前更强;台风登陆后通过低层辐合获得了大量水汽,眼墙区强劲的上升运动将低层辐合的水汽向中上层输送,在眼墙附近凝结产生大量的非绝热加热;非绝热加热不仅增暖气柱、增加位能还影响位能向动能的转换,虽然台风登陆后陆面摩擦显著加大,但气压梯度力所做的正功足以补偿摩擦耗散的动能,因而Bill能在登陆后长时间维持。     

成熟台风边界层作用的数值研究

利用ＴＬ６模式，在对一次台风过程成熟阶段进行成功模拟的基础上，通过各种对比试验，研究了成熟台风边界层的作用。结果表明：在２４小时内，台风边界层内各种通量的垂直输送对其路径影响很小而对成熟台风的维持却有非常重要的作用。其中，潜热输送成为成熟台风的主要能源，其影响最为重要。感热输送对成熟台风几乎无影响。边界层的动量垂直输送具有双重作用，摩擦辐合使上升运动增大，但明显对下层涡旋有削弱作用，这近似于在台风     

守恒系统中台风强度变化及其可能因子的数值研究

用一个高分辨率的f平面正压涡度方程模式,实施了时间积分为36h的21组试验,研究相邻中尺度涡旋与台风涡旋的相互作用。结果指出:这种相互作用能否导致台风加强,取决于两类因子:一是台风涡旋最大风速的取值以及圆形基流切变的强弱;二是切变基流中的中尺度涡旋的自身条件,包括中尺度涡旋的分布、尺度、强度和结构。台风强度与初始中尺度涡旋的尺度、强度之间存在着非线性的联系。     

NUMERICAL STUDY OF THE ABNORMAL TRACK OF TYPHOON MAGGIE

Typhoon Maggie (1999) interacted with another tropical depression system and moved along a west-southwest track that is somewhat abnormal during its pre-landing stage. Two numerical experiments are carried out in this paper to study the effect of the interaction on the track of typhoon Maggie using the mesoscale numerical weather prediction model system with a tropical cyclone bogusing scheme developed by Center for Coastal and Atmospheric Research, the Hong Kong University of Science and Technology. Results show that the cyclone system interacting with Maggie is the main factor for the abnormal track of Maggie.     

登陆我国台风研究概述

首先对登陆我国台风活动的气候特征分析指出，登陆我国的台风频数存在明显的月际、年际和年代际差异；登陆台风具有明显的周期特征和时间日变化特征；并指出了登陆我国台风与厄尔尼诺的联系。对中心最大风速≥17．2m/s的登陆台风移动趋势进行了统计分析，结果表明不同移动趋势的登陆台风频数不仅与季节有关，还与登陆地段有关。其次总结了近几十年有关登陆台风研究的成果。     

A CLOUD-RESOLVING MODELING STUDY OF SURFACE RAINFALL PROCESSES ASSOCIATED WITH LANDFALLING TYPHOON KAEMI(2006)

The detailed surface rainfall processes associated with landfalling typhoon Kaemi(2006) are investigated based on hourly data from a two-dimensional cloud-resolving model simulation. The model is integrated for 6 days with imposed large-scale vertical velocity, zonal wind, horizontal temperature and vapor advection from National Center for Environmental Prediction (NCEP) / Global Data Assimilation System (GDAS) data. The simulation data are validated with observations in terms of surface rain rate. The Root-Mean-Squared (RMS) difference in surface rain rate between the simulation and the gauge observations is 0.660 mm h^-1, which is smaller than the standard deviations of both the simulated rain rate (0.753 mm h^-1) and the observed rain rate (0.833 mm h^-1). The simulation data are then used to study the physical causes associated with the detailed surface rainfall processes during the landfall. The results show that time averaged and model domain-mean P_s mainly comes from large-scale convergence (Q_WVF) and local vapor loss (positive Q_WVT). Large underestimation (about 15%) of P_s will occur if Q_WVT and Q_CM (cloud source/sink) are not considered as contributors to P_s. Q_WVF accounts for the variation of P_s during most of the integration time, while it is not always a contributor to P_s. Sometimes surface rainfall could occur when divergence is dominant with local vapor loss to be a contributor to P_s. Surface rainfall is a result of multi-timescale interactions. Q_WVE possesses the longest time scale and the lowest frequency of variation with time and may exert impact on P_s in longer time scales. Q_WVF possesses the second longest time scale and lowest frequency and can explain most of the variation of P_s. Q_WVT and Q_CM possess shorter time scales and higher frequencies, which can explain more detailed variations in P_s. Partitioning analysis shows that stratiform rainfall is dominant from the morning of 26 July till the late night of 27 July. After that, convective rainfall dominates till about 1000 LST 28 July. Before 28 July, the variations of in rainfall-free regions contribute less to that of the domain-mean Q_WVT while after that they contribute much, which is consistent to the corresponding variations in their fractional coverage. The variations of Q_WVF in rainfall regions are the main contributors to that of the domain-mean Q_WVF, then the main contributors to the surface rain rate before the afternoon of 28 July.