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1.
高拴柱 《热带气象学报(英文版)》2001,7(2):209-217
Using the T63L16 analysis data with the resolution of 1.875╳1.875 degree of latitude and longitude
obtained from National Meteorological Center (NMC) and the real central position information of tropical
cyclone (referred to as TC hereafter) numbered by NMC, the basic environmental geostrophic flow at 126
time levels of 25 TCs in 1996 are calculated. The vertical distribution features of the flows are analyzed. Besides, the deviation of real TC tracks from the flows (referred as steering deviation hereafter, namely, the deviation between the real central position of TC and the position calculated according to the steering flow) is also investigated. The result shows that the steering deviation would be different if the domain used to calculate the steering flow is different. The present paper obtains the optimum domain size to calculate the steering flow. It is found that the steering deviation is related to the velocity of steering flow and the initial latitude and intensity of TC itself, and that TC motion has relationship with the vertical shear structure of environmental geostrophic flow. The result also shows that the optimum steering flow is the deep-layer averaged basic flow from 1000 hPa to 200 hPa. Having the knowledge of these principle and features would help make accurate forecast of TC
motion. 相似文献
2.
Initial mesoscale vortex effects on the tropical cyclone(TC) motion in a system where three components coexist(i.e.,an environmental vortex(EV),a TC,and mesoscale vortices) were examined using a barotropic vorticity equation model with initial fields where mesoscale vortices were generated stochastically.Results of these simulations indicate that the deflection of the TC track derived from the initial mesoscale vortices was clearly smaller than that from the beta effect in 60% of the cases.However,they may have a more significant impact on the TC track under the following circumstances.First,the interaction between an adjacent mesoscale vortex and the TC causes the emergence of a complicated structure with two centers in the TC inner region.This configuration may last for 8 h,and the two centers undergo a cyclonic rotation to make the change in direction of the TC motion.Second,two mesoscale vortices located in the EV circulation may merge,and the merged vortex shifts into the EV inner region,intensifying both the EV and steering flow for the TC,increasing speed of the TC. 相似文献
3.
A Statistical Analysis on the E ect of Vertical Wind Shear on Tropical Cyclone Development 
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下载免费PDF全文 Using tropical cyclone (TC) best track and intensity of the western North Pacific data from the Joint TyphoonWarning Center (JTWC) of the United States and the NCEP/NCAR reanalysis data for the period of 1992-2002, the effects of vertical wind shear on TC intensity are examined. The samples were limited to the westward or northwestward moving TCs between 5°N and 20°N in order to minimize thermodynamic effects. It is found that the effect of vertical wind shear between 200 and 500 hPa on TC intensity change is larger than that of the shear between 500 and 850 hPa, while similar to that of the shear between 200 and 850 hPa. Vertical wind shear may have a threshold value, which tends to decrease as TC intensifies. As the intensifying rate of TC weakens, the average shear increases. The large shear has the obvious trend of inhibiting TC development. The average shear of TC which can develop into typhoon (tropical depression or tropical storm) is below 7 m s-1 (above 8 m s-1). 相似文献
4.
Seasonal modulations of different impacts of two types of ENSO events on tropical cyclone activity in the western North Pacific 总被引：2，自引：0，他引：2
The paper examines different impacts of eastern Pacific warm/cold (EPW/EPC) and central Pacific warm/cold (CPW/CPC) events on tropical cyclones (TCs) in the western North Pacific (WNP) by considering the early season of April–June (AMJ), the peak season of July–September (JAS) and the late season of October–December (OND). During AMJ, EPW (EPC) is associated with a significant increase of the TC genesis number in the southeastern (southwestern) sub-region of the WNP, but no class of El Niño-Southern Oscillation (ENSO) events shows a significant change in the TC lifetime and intensity. During JAS, EPW corresponds to an increase (decrease) of the TC genesis number in the southeastern (northwestern) sub-region, but CPW shows no significant change. EPC increases the TC genesis in the northwestern and northeastern sub-regions and decreases the genesis in the southwestern sub-region, whereas CPC suppresses the genesis in the southeastern sub-region. Both the lifetime and intensity of TCs are increased in EPW, but only a shortened lifetime is seen for CPC. During OND, EPW reduces the TC genesis in the southwestern and northwestern sub-regions, whereas CPW enhances the genesis in the southeastern sub-region. Over the South China Sea, CPW and CPC show a significant decrease and increase of the TC genesis, respectively. The TC lifetime is significantly longer in both EPW and CPW and shorter in EPC, and TCs tend to be more (less) intense in EPW (CPC). All of these variations are consistent with the development of ENSO-related SST anomalies during different seasons and are supported by distributions of the genesis potential index—a combination of large-scale oceanic and atmospheric factors that affect TC activity. TCs in the WNP mainly take the straight westward, northwestward and recurving tracks. During AMJ of EPW years, the TC steering flow patterns favor the recurving track and suppress the straight westward and northwestward tracks. During JAS, EPW is associated with the steering flows that are unfavorable for TCs to move northwestward or westward, whereas CPW favors the northwestward track and suppresses the straight westward track. The steering flow patterns during OND are similar to those during JAS, except that EPC may increase the possibility of the northwestward track. 相似文献
5.
热带气旋运动的动力学研究进展 总被引：30，自引：7，他引：23
热带气旋运动是由各种形式的外部强迫、内部过程及其相互作用所决定的。特别是环境气流与气旋环流以及β效应之间的相互作用可以产生次级的非对称气流,使热带气旋偏离大尺度环境气流的引导。这种偏差,被称为广义的β漂移。本文讨论了控制β漂移的物理因子和物理过程,尤其是涡旋结构与环境气流切变对它的影响,以及β漂移在热带气旋路径预报上的应用。另外,还总结了双台风相互作用、热带气旋摆动和与下垫面强迫有关的物理过程的影响。 相似文献
6.
西北太平洋热带气旋移动方向变化异常的环流特征 总被引：3，自引：2，他引：1
基于中国气象局和上海台风研究所整编的1972-2011年热带气旋(TC)best-track资料,采用极端天气气候事件定义的百分位法确定TC移动方向异常变化的阈值,利用Lanczos滤波法将大气环流分解成为季节内振荡(MJO)、准两周振荡(QBW)和天气3种尺度环流场,研究这3种尺度环流对热带气旋在南海地区异常北折的影响。结果表明:近40 a的资料统计显示,热带气旋12 h内移向逆时针方向偏转50°以及顺时针方向偏转47°为TC移动方向变化的95%分位数值,将12 h移动方向变化大于该数值的TC定义为移动方向变化异常。TC异常路径平均每年发生2.68次,9月份发生的概率最大,约为7%,最常发生在南海海域。分析3个发生在南海地区热带气旋异常北折的引导气流发现,在TC转向前,向西的引导气流纬向速度减慢,经向分量先向南加速,随后突然转为向北加速。天气尺度对应的引导气流对TC异常右偏影响最为明显,对流层中高层热带气旋中心东南侧强天气尺度西南气流引导TC异常右偏。 相似文献
7.
国家气象中心台风路径数值预报模式自1996年6月投入业务运行以来, 一直在背景场中采用经验平滑滤波技术消除浅台风和嵌入轴对称的台风bogus涡旋技术。但事实上, 在采用经验平滑技术消除背景场中弱的位置不准确的浅台风涡旋同时, 也滤除了台风中心周围一些宝贵的非对称气流结构, 同时, 由于实际的台风涡旋结构是非对称的, 因而对采用轴对称涡旋的模式初始场而言, 或多或少的贡献了一些模式预报结果的路径误差。为了调查这部分非对称结构对台风预报路径误差的影响, 从T213L31全球谱模式提供的背景场中抽取浅台风周围的非对称流场, 将之加入到轴对称的台风bogus涡旋中。初步的个例试验发现, 加入非对称流场后, 能有效地减少台风路径预报误差。 相似文献
8.
Anil Kumar James Done Jimy Dudhia Dev Niyogi 《Meteorology and Atmospheric Physics》2011,114(3-4):123-137
The predictability of Cyclone Sidr in the Bay of Bengal was explored in terms of track and intensity using the Advanced Research Hurricane Weather Research Forecast (AHW) model. This constitutes the first application of the AHW over an area that lies outside the region of the North Atlantic for which this model was developed and tested. Several experiments were conducted to understand the possible contributing factors that affected Sidr??s intensity and track simulation by varying the initial start time and domain size. Results show that Sidr??s track was strongly controlled by the synoptic flow at the 500-hPa level, seen especially due to the strong mid-latitude westerly over north-central India. A 96-h forecast produced westerly winds over north-central India at the 500-hPa level that were notably weaker; this likely caused the modeled cyclone track to drift from the observed actual track. Reducing the model domain size reduced model error in the synoptic-scale winds at 500?hPa and produced an improved cyclone track. Specifically, the cyclone track appeared to be sensitive to the upstream synoptic flow, and was, therefore, sensitive to the location of the western boundary of the domain. However, cyclone intensity remained largely unaffected by this synoptic wind error at the 500-hPa level. Comparison of the high resolution, moving nested domain with a single coarser resolution domain showed little difference in tracks, but resulted in significantly different intensities. Experiments on the domain size with regard to the total precipitation simulated by the model showed that precipitation patterns and 10-m surface winds were also different. This was mainly due to the mid-latitude westerly flow across the west side of the model domain. The analysis also suggested that the total precipitation pattern and track was unchanged when the domain was extended toward the east, north, and south. Furthermore, this highlights our conclusion that Sidr was influenced from the west side of the domain. The displacement error was significantly reduced after the domain size from the western model boundary was decreased. Study results demonstrate the capability and need of a high-resolution mesoscale modeling framework for simulating the complex interactions that contribute to the formation of tropical cyclones over the Bay of Bengal region. 相似文献
9.
Simulated impacts of two types of ENSO events on tropical cyclone activity in the western North Pacific: large-scale atmospheric response 总被引：1，自引：0，他引：1
The present paper uses an atmospheric general circulation model to explore large-scale atmospheric response to various El Niño-Southern Oscillation events associated with tropical cyclone (TC) activity in the western North Pacific. The simulated response is basically consistent with and confirms the observed results. For eastern Pacific warm (EPW) event, anomalously wet ascent occurs over the tropical central/eastern Pacific and dry descent is over the western Pacific. This Walker circulation is associated with anomalous low-level convergence, reduced vertical wind shear (VWS), and enhanced genesis potential index (GPI) in the southeast sub-region. These are consistent with the observed increase of the TC formation in the southeast sub-region but decrease in the northwest sub-region during July–September (JAS) and the increase in the southwest and northwest sub-regions during October–December (OND). In addition, the strong westerly anomalies of the TC steering flow prevail in the East Asian coast, suppressing the TC northwestward or westward tracks. For eastern Pacific cold (EPC) event, all of the simulated variables show almost a mirror image of EPW. For central Pacific warm event, the anomalous Walker circulation shifts westward because of the westward shift of the maximum SST anomaly forcing. The anomalous subsidence associated with the western branch of the Walker circulation during OND shifts northward to the South China Seas, resulting in a decrease of the TC genesis there. The TC steering flow patterns during JAS are favorable for TCs to make landfall over Japan and Korea. Compared with EPC, the descending motion in the central/eastern Pacific is much stronger for central Pacific cold (CPC) event, accompanied by more enhanced VWS and reduced GPI in the southeast sub-region. Therefore, CPC provides a more adverse environment to the TC formation there during JAS and OND, consistent with the observed decrease of TC formation there. Moreover, the easterly anomalies of the TC steering flow dominate the tropics during JAS, enhancing TC activity in the east coast of China. Additionally, the convection over the western Pacific moves to the South China Sea during OND, favoring the TC genesis there. 相似文献
10.
利用TOVS资料分析了2000年几个热带气旋的结构,发现与经典概念模型所描述的结构有一定的差异,主要表现在:(1)在水平结构上,非对称结构呈多样性,高度场的低层低值中心(或高层高值中心)与温度场的高值中心并不一定重合;(2)在垂直结构上,高度场的低层低值距平与高层高值距平的配置也呈多样性,特别是存在上、下层距平中心倾斜,或高层只是处于高压区的边缘,不存在明显的高值距平中心与热带气旋相对应.还参照TOVS中的热带气旋结构,进行了修订热带气旋数值预报模式系统中人造台风模型(台风BOGUS)结构的研究,发现修订后的台风BOGUS 能够更好地与环境场协调,并且能对热带气旋的路径预报取得较好的效果.这一方面说明了台风BOGUS的结构对其路径预报有较大的影响,另一方面也说明利用TOVS资料中的热带气旋结构能改善热带气旋路径预报.这也为台风BOGUS的修订和发展提供了依据. 相似文献
11.
12.
采用谱逼近方法减小大尺度环境场模拟偏差,通过地形敏感性试验,研究吕宋岛山脉地形高度对台风Megi(2010)过岛阶段路径偏折的影响。模拟试验表明,谱逼近700 hPa高度层以上天气尺度风场分量的数值试验不仅能够反映大尺度环流对台风路径的引导作用,同时保留了中低层环流对地形影响的响应,较为准确地反映了Megi靠近和登陆吕宋岛过程中的持续南压过程,以及离开吕宋岛后的突然北折过程。在此模拟基础上,通过对地形高度敏感性试验结果诊断和影响区域空气质点进行后向轨迹分析,表明在台风向山脉靠近过程中,台风外围和内核环流均受地形影响,迎风坡存在明显气流辐合,有利于台风流场与南北向山脉之间出现北风急流和轨迹汇聚带,从而产生狭管效应,造成台风移动路径南折;而台风过山后,不仅受到地形次生低压涡旋的吸引,其东侧同样出现以南风急流和轨迹汇聚为特征的狭管效应,有利于台风路径向北偏折。 相似文献
13.
本文从四个方面检验分析了ECMWF 2009—2015年西北太平洋热带气旋集合平均预报性能。结果表明：集合预报对路径的预测能力逐年提高,对强度预报整体偏弱。随着热带气旋强度增强,集合预报对移速和移向的预测能力提高,而移向预报偏左、移速预报偏慢、强度预测偏弱的现象较明显。将影响热带气旋的引导气流分为偏强、中等、偏弱三类,引导气流偏弱时热带气旋移动偏慢,因此移向预报的不确定性大;而引导气流偏强时热带气旋移向明确,只是移速预报不稳定。进入南海的三类路径热带气旋,集合预报对西行、西北行两类的移速、移向预报效果较好,而西行后北折的预报较差,在热带气旋北折前,移向预报发散度很大,向北转折后移向趋于稳定,移速预报的误差相对较大。这几种情形的检验结果,在热带气旋集合预报的业务应用中值得注意。 相似文献
14.
全球数值模式中的台风初始化Ⅰ:方案设计 总被引：2，自引：0，他引：2
由于缺少大量有效的观测资料,台风初始化对数值天气预报业务模式而言,仍然是一个悬而末决的难题.中国国家气象中心自从1996年将台风数值预报系统投入业务运行以来,一直使用经验的人造bogus涡旋台风初始化技术.实际上,不同时期的台风有着不同的环流结构,即使同一个台风在不同的生命期也具有不同的结构特征,而这些结构特征的差异并不能依靠现有的bogus涡旋技术体现出来,这种主观方法的统一性与台风在时空上的差异性形成了强烈的反差.最近,基于国家气象中心全球资料分析同化-预报循环系统,设计和发展了一套新的台风初始化业务方案,它主要由初始涡旋形成、涡旋重定位和涡旋调整3部分过程组成.相比于业务中使用的人造bogus涡旋台风初始化方案,新方案在很大程度上减少了人为因素对台风涡旋结构的影响,而更多地是依靠数值模式自身的动力和物理过程来协调约束产生三维空间的涡旋结构.应用新方案,文中对生成于西北太平洋的2006年0605号台风格美(Kaemi)进行了数值试验,初步分析表明,新方案在实现台风涡旋环流结构的初始化方面效果较好,同时,对台风格美多个时次的预报结果也显示,相比于业务使用的bogus方案而言,新方案对台风路径平均预报误差有了大幅度的降低. 相似文献
15.
利用WRF模式对2016年6月30日—7月6日长江流域的一次大暴雨天气过程中的低空急流进行数值模拟,在成功模拟低空急流基础上,分析此次急流过程中可能的影响机制;同时对地形高度进行敏感性试验,分析地形因素对此次低空急流可能的影响。(1)此次低空急流发生时,东侧为西太平洋副热带高压,西侧则为西南涡。这种“东高西低”的高低压配置为低空急流的形成与发展提供了有利的背景场。(2)高空急流和低空急流的耦合作用是低空急流发展的一个重要背景条件。(3)垂直方向高空动量不断下传为低空系统的发展提供了动力支持,是低空急流发生的一个重要条件。(4)逆温和垂直风切变之间的正反馈机制是低空急流形成与加强的因素之一。(5)山体在急流生成及发展过程中对气流有摩擦和阻挡作用,这种阻挡作用随着山体地形高度的增加而有所加强,同时山脉的走向会改变原始的风向,使得急流前端超前或滞后。青藏高原有强背风波效应,它的绕流和挤压作用会使得低空气流表现为狭长的带状,使动量更加聚集从而风速增加形成低空急流。 相似文献
16.
The influence of intraseasonal oscillation (ISO) on TC genesis over the northwestern Pacific is studied through comparing analyses of the more and less TC years from 1979 to 2006. It is indicated that the ISO strongly affects the TC genesis. In the years for more TC genesis, the ISO is weak and propagates insignificantly in the area to the west of the Philippines, but the ISO is strong in the area to the east of the Philippines and propagates significantly northwestward. In this situation, the Walker cell shifts gradually westward from the tropical western Pacific to the tropical eastern Indian Ocean. Convergent winds appear in the lower atmosphere while divergent winds in the upper atmosphere, suggesting the presence of enhanced ascending flow over the 140-160°E region and a favorable condition for TC genesis. Moreover, in the years for less TC genesis, the ISO gradually becomes stronger in the area to the west of the Philippines and significant eastward propagation prevails from the eastern Indian Ocean to the area around 120°E; the ISO is weak in the area to the east of the Philippines. During these years, the Walker circulation gradually moved eastward, with convergent winds in the upper troposphere and divergent winds in the lower troposphere. Sinking motion was significant, unfavorable for the TC genesis over the Northwestern Pacific. 相似文献
17.
The possible changes of tropical cyclone(TC) tracks and their influence on the future basin-wide intensity of TCs over the western North Pacific(WNP) are examined based on the projected large-scale environments derived from a selection of CMIP5(Coupled Model Intercomparison Project Phase 5) models. Specific attention is paid to the performance of the CMIP5 climate models in simulating the large-scale environment for TC development over the WNP. A downscaling system including individual models for simulating the TC track and intensity is used to select the CMIP5 models and to simulate the TC activity in the future.The assessment of the future track and intensity changes of TCs is based on the projected large-scale environment in the21 st century from a selection of nine CMIP5 climate models under the Representative Concentration Pathway 4.5(RCP4.5)scenario. Due to changes in mean steering flows, the influence of TCs over the South China Sea area is projected to decrease,with an increasing number of TCs taking a northwestward track. Changes in prevailing tracks and their contribution to basin-wide intensity change show considerable inter-model variability. The influences of changes in prevailing track make a marked contribution to TC intensity change in some models, tending to counteract the effect of SST warming. This study suggests that attention should be paid to the simulated large-scale environment when assessing the future changes in regional TC activity based on climate models. In addition, the change in prevailing tracks should be considered when assessing future TC intensity change. 相似文献
18.
利用欧洲中期天气预报中心的ERA-Interim再分析资料驱动CWRF模式对1982-2016年中国近海的热带气旋活动进行了模拟,分析了CWRF对热带气旋频数季节、年际变化和路径的模拟能力,并探讨了环境场模拟对热带气旋模拟的影响。结果表明:CWRF能够合理模拟热带气旋频数的季节和年际变化,但模拟的频数较观测总体偏低,季节变化模拟总体优于年际变化的模拟;模式基本上能模拟出热带气旋路径密度的空间分布,但CWRF明显总体低估了气旋路径密度。进一步分析发现,模式模拟的环境场对模拟结果具有十分重要的影响。850 hPa气旋性与反气旋性环流异常对热带气旋频数影响显著;200 hPa反气旋性环流异常与东亚西风急流对热带气旋路径影响较大;副高会影响洋面对流运动从而影响热带气旋频数,其南侧偏东风则会影响热带气旋路径;垂直风切变偏小,在不同纬度对热带气旋的影响是不同的。 相似文献
19.
鞍型场是一种特殊的流场,鞍点附近气压梯度很小,风场很弱,引导气流不明显。当热带气旋进入鞍型场时,会表现为停滞、打转、突然转向等异常路径。采用NCEP资料对2011年热带气旋"梅花"路径和大尺度形势场分析结果表明,在其整个生命史中出现三次移动路径转折,热带气旋进入鞍型场后,出现在鞍点附近停滞、移动缓慢、突然转向等异常路径。利用理想变形场和兰金涡旋相结合的鞍型场作为背景场,用梯度风平衡构造了理想热带气旋,分别考虑了科氏参数为常数和β平面近似两种情况,利用二维浅水模式对热带气旋处于鞍点和收缩轴附近不同位置的情况进行了数值对比试验。当科氏参数为常数时,处于鞍点位置的热带气旋在鞍点停滞;而当采用β平面近似时,处于鞍点位置的热带气旋向东北低压一侧移动,并和低压合并。当初始热带气旋处于鞍点南侧的收缩轴上以及偏东或偏西100 km时,会出现三种截然不同的移动路径。试验结果表明:鞍型场对热带气旋有"陷阱"作用。当热带气旋进入到鞍型场区并接近鞍点时,在β漂移和弱引导气流作用下,可能陷入鞍点附近区域,移动缓慢,出现异常路径,也可能沿着膨胀轴向偏东或偏西方向移动,使得热带气旋突然转向。热带气旋的移动对其和收缩轴的相对位置十分敏感,数十千米的偏差可能会导致截然相反的移动路径。 相似文献
20.
A statistical analysis of the initial vortexes leading to tropical cyclone(TC) formation in the western North Pacific(WNP) is conducted with the ECMWF ERA5 reanalysis data from 1999 to 2018. It is found that TCs in the WNP basically originate from three kinds of vortexes, i.e., a mid-level vortex(MV), a low-level vortex(LV), and a relatively deep vortex with notable vorticity in both the lower and middle troposphere(DV). Among them, LV and DV account for 47.9% and24.2% of tropical cyclogenesis e... 相似文献