台风榴莲(2001)在季风槽中生成的机制探讨   总被引：2，自引：0，他引：2  

张文龙  张大林  王昂生  崔晓鹏 《气象学报》2009,67(5):811-827

利用NCEP 1°×1°分析资料、TMI海温资料、卫星云图资料对季风槽中南海台风榴莲(2001)生成机制进行了分析,揭示了大尺度环境流场、温暖洋面、中尺度对流活动对热带气旋(TC)生成的控制作用.结果表明,水平风速垂直切变的演变在一定程度上指示着TC在暖湿洋面上生成的时间,水平风速垂直切变由强向弱转变,在TC发生前18小时迅速减小到10 m/s,随后在10 m/s以下维持少变,垂直切变的变化主要反映了对流层高层环流形势的演变;在对流层中低层,季风槽的形成和加强对TC的生成有重要作用,由于热带温暖洋面作用,季风槽首先表现出有利于单体对流和带状对流发生发展的条件性对流不稳定特征,随着季风槽的加强,季风槽进一步表现出有利于中尺度扰动发生发展的正压不稳定特征;季风槽槽线南侧的低空急流的经向分布很宽广,由105°E越赤道气流和中南半岛偏西气流(其源头是索马里越赤道低空急流)汇合而成,急流的加强活动具有经向差异,由于边界层高θ_e空气辐合抬升产生两条经向距离约300 km的显著带状对流云系,槽线南侧风速分布的经向差异导致两条带状云系发生追赶,并逐步在季风槽底部槽线附近合并加强为MCC,进而导致中尺度涡旋(MCV)的产生并最终发展成为TC.分析结果还表明,为深对供应丰富对流有效位能的主要是来自台风发生区域本地南海暖洋面的地面热通量,南海暖洋面对TC生成有重要贡献.台风榴莲的生成是一个多尺度相互作用过程,主要包括涡旋对流热塔、与带状对流云系伴随的涡度带的升尺度,涡度带合并成长为MCV,以及大尺度条件对TC在季风槽中生成的时间及地点的控制作用等.  相似文献   

A Study on a Heavy Rainfall Event Triggered by an Inverted Typhoon Trough in Shandong Province   总被引：2，自引：0，他引：2       下载免费PDF全文

ZHAO Yu  CUI Xiaopeng  WANG Jianguo 《Acta Meteorologica Sinica》2009,23(4):468-484

A heavy rainfall event that occurred in Shandong Province in 26 28 August 2004 was caused mainly by Typhoon Acre and cold air activities related to a westerly trough. The event was triggered by an inverted typhoon trough, which was closely associated with the intensification of the low-level southeasterly flow and the northward transport of heat and momentum in the periphery of the typhoon low. A numerical simulation of this event is performed using the nonhydrostatic mesoscale model MM5 with two-way interactive and triply-nested grids, and the structure of the inverted typhoon trough is studied. Furthermore, the formation and development mechanism of the inverted typhoon trough and a mesoscale vortex are discussed through a vorticity budget analysis. The results show that the heavy rainfall was induced by the strong convergence between the strong and weak winds within the inverted typhoon trough. Dynamic effects of the low-level jet and the diabatic heating of precipitation played an important role in the development of the inverted typhoon trough and the formation of the mesoscale vortex. The vorticity budget analysis suggests that the divergence term in the low troposphere, the horizontal advection term, and the convection term in the middle troposphere were main contributors to positive vorticity. Nonetheless, at the same pressure level, the effect of the divergence term and that of the adveetion term were opposite to each other. In the middle troposphere, the vertical transport term made a positive contribution while the tilting term made a negative contribution, and the total vorticity tendency was the net result of their counteractions. It is found that the change tendency of the relative vorticity was not uniform horizontally. A strong positive vorticity tendency occurred in the southeast of the mesoscale vortex, which is why the heavy rainfall was concentrated there. The increase of positive vorticity in the low （upper） troposphere was caused by horizontal convergence （upward transport of vorticity from the lower troposphere）. Therefore, the development of the inverted typhoon trough and the formation of the mesoscale vortex were mainly attributed to the vorticity generated in the low troposphere, and also the vertical transport of vorticity from the low and middle troposphere.  相似文献   

塔中及相邻地区早奥陶世沉积格局新论     

严威  王兴志  王振宇  杨海军  冉丽君 《沉积学报》2010,28(6):1090-1097

前人的观点认为,早奥陶世的塔里木盆地是一个统一的“大碳酸盐岩台地”,斜坡相呈马蹄形发育在古城—轮南一线。通过对塔中地区满加1井—塔中29井一线及相邻地区下—中奥陶统的岩石学、沉积学和地震地层学等方面的研究,发现这一线的下奥陶统主要由一套较深水的斜坡及海槽沉积构成,其地层厚度和地震反射特征也明显与周边地区不同,认为塔中及相邻地区在早奥陶世期间已经从早期的塔里木“大碳酸盐台地”中分化独立出来,分裂成塔中—巴楚台地、古城台地、塘南台地三块孤立台地,以塔北隔海相望。各孤立台地周缘发育台地边缘高能礁滩沉积体,呈条带状展布,主要由中高能粒屑滩组成;向内相变为台地相,发育台内滩、台内洼地、滩间海等亚相;向外进入较深水的斜坡—海槽沉积区,从而确立了塔中及相邻地区早奥陶世新的区域沉积格局。新沉积格局的确立,对于确立下奥陶统新的有利勘探区带具有重要的理论和现实意义,大大提升了研究区下奥陶统的油气勘探战略地位。  相似文献   

凹槽流痕在赣北前寒武纪地层中的发现及意义   总被引：1，自引：0，他引：1  

马长信 《地质论评》1995,41(4):371-377

凹槽流痕是在等深流作用下，在层面上产生的一种冲刷痕迹原生沉积构造，一般较为罕见，其长轴方向与等深流方向一致，沿大陆斜坡走向分布，赣北晚元古代早期程浪群计林的紫红色条带状细粒碎屑沉积浅变质岩的层面上，有密集而清晰的凹槽流痕分布。  相似文献   

初夏昆明罕见大暴雨分析   总被引：3，自引：0，他引：3  

解明恩  李贵福 《气象》1994,20(1):34-37

１９８６年６月６－７日，云南昆明出现了１９５１年以来一次最大暴雨。天气学与诊断分析表明，初夏云南可产生单点局地大暴雨，量级与盛夏、秋季相当。５００ｈＰａ干冷槽东移，７００ｈＰａ双涡吸引旋转西移，地面弱冷空气诱发静止锋锋生，强垂直风切变，昆明上空出现正反环流圈是该次过程的主要特征，与低纬度原地区区域性大－暴雨特征不同。  相似文献   

冬季青藏高原对东移大槽动力影响的研究 （Ⅱ）理想初始场、地形场的构造和数值试验方案的设计   总被引：3，自引：0，他引：3  

焦彦军  钱正安 《高原气象》1994,(4)

为了以数值试验手段定量地再现青藏高原地形对冬季东移大槽的影响，也同时讨论冬季亚洲不同高空环流形势下地形对东移槽影响的差别，本文使用我所６层有限区域格点模式，首先根据该模式对初始场的需要，也源于冬季亚洲地区高空流型的特点，构造了以基本斜压西风气流加高空西风急流，并在其上迭加正弦波槽扰动为主要特征的环境流场等的理想初始场及理想地形场。然后，根据不同流场成员和地形的组合，设计了１３个数值模拟试验。接着，利用整层无辐散初始化方案，固定侧边界条件，对各试验积分４—５天，最后分析各试验中东移槽的行为。本研究第三部分的模拟试验结果的分析表明〔１９〕，模式计算稳定，模拟结果合理，说明文中理想场的构造是协调的、合理的，也比较接近实际。侧边界条件及初始场的预处理也大体是合适的。  相似文献   

中国晚奥陶世岩相古地理   总被引：10，自引：8，他引：2       下载免费PDF全文

冯增昭  彭勇民  金振奎  鲍志东 《古地理学报》2004,6(2):127-139

本文是笔者等的中国早、中、晚寒武世和早、中奥陶世岩相古地理诸文的继续。在对华北地区、华南地区和西北地区寒武纪和奥陶纪定量岩相古地理研究及编图成果的基础上,结合其他地区（主要是蒙兴地区、昆仑秦岭地区、西藏地区、海南岛和台湾地区）的地质资料,编制出了中国晚奥陶世岩相古地理图,并撰写出本文。华北地区、华南地区和西北地区的研究程度较高,其岩相古地理图和文字论述都是定量的。其他地区的研究程度较低,其岩相古地理图和文字论述则是定性的或概略性的。在中国晚奥陶世,早、中、晚寒武世和早、中奥陶世一直存在的“两槽和三台相间分布”的岩相古地理基本格局已经改变,天山北山蒙辽吉槽地中的北山槽地和蒙辽吉槽地已不再是槽地而变成了台地。因此,准噶尔台地、北山台地、蒙兴台地、蒙辽吉台地和华北台地就连在一起了,形成了一个庞大的北方台地群。这是一个重大变化。其他古地理单元也与以前各世的大不相同或有所不同。这是晚奥陶世晚期大规模海退的结果。  相似文献   

NUMERICAL SIMULATION OF EXTREMELY HEAVY RAIN AND MESO-β SCALE LOW VORTEX IN INVERTED TYPHOON TROUGH^*          下载免费PDF全文

JIANG Yongqiang  WANG Changyu  ZHANG Weihuan  CHEN Zhongyi 《Acta Meteorologica Sinica》2004,18(2):195-210

Large-scale and mesoscale analyses are made for extremely heavy rain(EHR) and meso-β scale low vortex(MSLV) in Jiading District of Shanghai Municipality during 6-7 July 2001.It is shown that the EHR forms in the situation of northern westerly trough linking together with southern inverted typhoon trough at northwest side of the West Pacific Ocean subtropical high. Numerical simulation is made using a 21-layer improved REM(regional η coordinate model) for this course.The results show that the precipitation forms earlier than MSLV.and the strong convergence in wind velocity mate(WVM) triggers the strong precipitation.The formative reasons of WVM.especially the weak wind velocity center are discussed,and the formative mechanisms of the MSLV and EHR are discussed using high spatial and temporal resolution modeloutput physical fields.The results show that the heavy rain releases latent heat and warms the air column,and enhances the low level positive vorticity that existed before.Then it causes the formation of MSLV.There is a positive feedback mechanism between low vortex and precipitation,so CISK must be an important mechanism.  相似文献   

Plate kinematics of the Western Mediterranean region during the Oligocene and Early Miocene     

Antonio Schettino  Eugenio Turco 《Geophysical Journal International》2006,166(3):1398-1423

The tectonic history of the Western Mediterranean region during the Oligocene and Early Miocene is illustrated through a series of plate reconstructions, from chron C13n to chron C6n. The reconstructions are based on a new interpretation of published magnetic anomaly data and two-ships seismic data, and their integration with known geological constraints, in order to determine style and timing of the backarc extension processes in the Liguro-Provençal, Valencia and Algerian basins. In particular, a reinterpretation of the regional magnetic anomaly field allowed the calculation of the instantaneous Euler poles associated with the motion of 11 microplates relative to Eurasia and Iberia. Furthermore, a quantitative analysis of the acoustic basement morphology and the balancing of deep crustal profiles were used to estimate the closure and pre-rift rotation angles associated with the Euler poles of opening of the Ligurian, Provençal, Valencia and Algerian basins. This rigorous reconstruction of the geometry of the pre-rift continental margins of Iberia and Eurasia could furnish important insights into the study of Mediterranean tectonics for older times.  相似文献   

藏西南纳木那尼峰地区第四纪以来的冰川演化          下载免费PDF全文

杨建强  易朝路  L.A.Owen  N.Davis 《第四纪研究》2006,26(2):211-219

藏西南纳木那尼峰地区第四纪以来经历了多阶段的冰川演化,遗留了各个阶段不同类型的冰川堆积地貌和冰川侵蚀地貌。文章通过对各阶段冰积地貌的分布范围、特征的描述,并根据保存程度确定其相对地貌年龄,初步认为本地区第四纪以来倒数第3次冰期发育了规模最大的冰原冰川,倒数第2次冰期时冰原缩小并逐渐解体,末次冰期以来完全解体为山谷冰川。根据本地区槽谷的形态特征及冰川堆积物的分布,认为本地区末次间冰期前后有一次活跃的构造运动。  相似文献