超强台风鲇鱼路径北翘预报分析

利用常规气象观测资料、实时业务数值预报模式、欧洲中期天气预报中心（ECMWF）ERA Interim全球再分析资料（1.5°×1.5°）以及NCEP全球再分析资料（1°×1°）,对1013号超强台风鲇鱼移入南海后路径突然北翘的原因进行了初步分析,并对业务数值预报模式及中日美三家综合业务预报的台风路径预报进行了检验。结果发现：南半球越赤道气流向北涌进致使赤道缓冲带北进与＂鲇鱼＂东侧的副热带高压脊合并是＂鲇鱼＂在南海路径发生突然北翘的主要原因;当业务数值预报模式出现较大分歧时,台风路径多模式集成预报或超级集合预报是解决数值预报较大分歧的有效途径,为此有必要加强台风路径多模式集成预报或超级集合预报综合应用平台的研发,并在此基础上进一步完善现有台风业务预报流程。     

回顾超强台风“布拉万”及其异常路径分析

2012年8月下旬,超强台风"布拉万"对东北地区造成极大影响。该台风路径属于北折异常路径,本文对该台风路径异常原因试做分析,结果表明:主要影响系统依然是西太平洋副热带高压的引导气流的作用,前期大陆低压槽的东移对西太平洋副热带高压有挤压作用,导致台风布拉万的主要影响气流转为偏西方向;大陆低压槽后期与西太平洋副热带高压的对峙时间较长,有较强的偏南气流,再加上台风"天秤"的双台风互旋作用,使台风"布拉万"被北抬,因此维持较长时间的向北方向移动。950-250 h Pa的深层次引导气流,与700 h Pa的引导气流与台风的移动速度也较一致。因此,注意大型环流场与引导气流的变化对台风的预报,依然具有非常重要的指导意义。     

强台风"珍珠"异常路径的特点、成因及预报

通过对强台风“珍珠”路径4个阶段的特点和影响因素的分析,特别是影响台风移动的诸多因子及其对“珍珠”西行北折异常路径所起的作用分析,发现:大尺度环境场的调整(副高脊线东退南落、越赤道气流的变化、弱冷空气的变化等),使环境场对“珍珠”的引导作用减弱。弱环境流场与“珍珠”的非线性相互作用是“珍珠”西行北折的主要原因。SST的分布也有利于“珍珠”的加强和热力结构的变化,并影响“珍珠”的路径。“珍珠”的水平结构变化,特别是其热力非对称结构的变化,对路径的影响更为明显。各种主、客观预报对“珍珠”的移动路径作出了几乎完美的预报。     

基于TIGGE资料的台风“鲇鱼”路径北翘成因分析

利用欧洲中期天气预报中心（ECMWF）集合预报资料,对比分析了成功预报“鲇鱼”北翘路径的成员（北翘组）和没有预报“鲇鱼”北翘路径的成员（西行组）的环境场及台风环流特点。结果显示:从环境场来看,在预报前期北翘组在“鲇鱼”北侧的副热带高压偏弱,副热带高压断裂东退发生的时间比西行组早,而在预报后期,北翘组西风槽比西行组强;而从“鲇鱼”环流来看,初始时刻北翘组和西行组存在明显不同的非对称结构,在后期预报中,北翘组“鲇鱼”环流范围明显比西行组大。北翘组“鲇鱼”环流初始时刻的非对称结构以及其南侧偏弱的低压环流使得“鲇鱼”环流后期偏大、东南侧及东侧偏南气流偏强,这有利于“鲇鱼”北侧副热带高压断裂东退和西风槽发展南移。      

台风“鲇鱼”异常路径的诊断分析和数值模拟

从高空环流和基本气流的演变对2010年第13号台风＂鲶鱼＂进入南海以后路径发生向北＂急翘＂的大环流形势进行分析,并应用wrf模式输出的高分辨率资料,对台风中心附近的风场、温度场和θse场的分布进行探讨,得出：＂鲇鱼＂进入南海后,路径发生向北＂急翘＂是由于青藏高压增强并向东移,致使其前部高空槽加深发展,切断了华南高压和副热带高压的联系,并使华南高压南落至中南半岛一带,使台风西行受阻,逐渐转为北移。同时越赤道气流的北涌,使基本气流从东北气流转为西南气流,北偏东移动趋势加大。500～700hPa两层引导气流与＂鲶鱼＂路径有很好的对应关系。最大风速区的水平和垂直结构将影响台风移动的路径,台风中心的有向风速低值区移动的趋势,最大风速区的垂直尺度的变化对台风移动有指导意义。温度场的水平和垂直分布也将影响台风的移动路径,西侧冷空气的入侵使台风偏西移动的趋势减弱,台风中心有向等厚度低值区移动的趋势。θse的高能舌的分布,有利台风向北或北偏东方向移动。     

云娜台风登陆前移向移速变化分析

云娜台风登陆前有两个明显的特征:台风路径西折和移动速度加快.本文对其进行分析,发现西风带长波调整引起副热带高压的加强和涡度场的变化是台风西折的主要原因;而500 hPa引导气流的加强、台风结构的变化以及台风与低涡之间的互旋导致台风加速.文中还对卫星云图和雷达回波的云系变化对台风路径和移速的变化的预报意义进行了分析.     

超强台风“天鹅”（2015）路径突变过程机理研究

本文采用中国气象局的最佳台风路径数据和美国国家环境预报中心1°×1°每6 h再分析资料作为研究工作的基本场,运用了分部位涡反演方法探讨影响2015年第15号超强台风“天鹅”路径突变的物理机制,得到以下结论:（1）就天气系统而言,“天鹅”整个移动过程中都受到周围环境场及引导气流的影响,主要的影响系统包括西北太平洋副热带高压、季风涡旋、邻近台风“艾莎尼”及台风外围反气旋;（2）定量分析了与各影响系统扰动位涡相关的引导气流矢量,发现整个过程中超强台风“天鹅”的移动始终受西北太平洋副热带高压的影响,其次是来自季风涡旋及台风外围反气旋的贡献,而当“天鹅”有向北转向趋势时,与外围反气旋相关的东北向引导气流导致了台风的路径北折;（3）进一步定量分析了总扰动位涡在不同高度层上相关引导气流的贡献,结果表明在垂直方向上对流层中层系统的引导气流矢量与“天鹅”的移动最为吻合,而形成于低层系统的偏南风气流与“天鹅”向北突然转向有着密切的联系,并在转向后逐渐向中高层发展增强。     

基于GRAPES模式模拟强台风“珍珠”数值分析

以T213L30模式产品及常规观测资料为基础,采用GRAPES数值预报模式对强台风“珍珠”（0601）的演变过程进行了数值模拟。结果表明,GRAPES模式对“珍珠”的加强、移动路径和产生的暴雨都有较好的预报能力,尤其是对“珍珠”南海西行突然顺转90°折向北行异常路径的预报较为理想,且登陆点预报准确。通过对形势场（500hPa高度场、海平面气压场）、物理量场（温度、涡度、垂直速度、散度）、流场的数值模拟分析,认为“珍珠”路径的转折变化与副热带高压的东撤南退、冷空气的变化、越赤道气流的变化、台风的非对称结构有关。     

“鲇鱼”异常路径分析

对1013号"鲇鱼"的异常路径分阶段进行天气学分析,发现影响鲇鱼路径的主要天气系统有副热带高压、高空槽、西南季风、冷空气,几者在鲇鱼的不同时期影响是鲇鱼路径异常的原因。两环副高之间存在缺口是鲇鱼前期有偏北分量的原因之一;东环西太副高西伸形成高压坝阻档鲇鱼北上;两环副高交替影响鲇鱼,路径由西北向转为西南向;冷空气南下至鲇鱼西侧阻挡其向西移动;高空槽前西南气流和低纬度西南季风是"鲇鱼"北折的原因。对比各家预报结果,发现日本对鲇鱼的路径和登陆点预报结果最好,热带所对于路径转折的趋势反映较好。     

越赤道气流不同波长分量对台风Megi（2010）路径偏折的影响与模拟检验

基于NCEP再分析资料和NOAA高分辨率海温资料,采用空间傅里叶滤波法,分析了台风Megi(2010)路径北折过程中越赤道气流强度随时间的变化,以及其不同波长分量对台风移动路径转折的影响,利用谱逼近方案的数值模拟对分析结果进行验证。结果表明,加里曼丹岛附近越赤道气流突然增强北涌对台风移动路径北折具有重要影响。经纬向波长为500km以上的低层风场分量的环流结构能明显反映出加里曼丹岛附近越赤道气流中的中尺度反气旋系统。模拟试验结果与分析结果一致,即环境风场的中尺度分量是影响台风路径北折的重要因子,其中经纬向波长为500 km以上风场分量体现了加里曼丹岛附近越赤道气流风场结构中的中尺度反气旋系统对台风路径的影响,因此,其模拟路径与观测路径最为接近。     

FACTORS AFFECTING THE TRACK OF TROPICAL CYCLONES AFTER LANDFALL IN EASTERN CHINA

The correlation and composite analysis are carried out in this paper to study major factors affecting the track of tropical cyclones (TCs) after their landfall in the east of China. The mid-tropospheric environmental steering flow is found to dominate the movement of a TC even after landfall, with the inertia and Coriolis force two other subordinates. A key region is discovered covering the east of China and Yellow Sea, in which the environmental flow significantly affects the movement of TCs making landfall in this part of China. When the subtropical high in this region strengthens and extends westward, accompanied by northward shrink of the westerly trough, the TC tends to move westward after landfall and disappear inland. However, when the subtropical high in this region weakens and shrinks eastward, accompanied by southward push of the westerly trough, the TC tends to recurve after landfall and re-enter the sea at a location to the north of the site of landfall. The environment before the landfall of a TC has little impact on its post-landfall track, which is sensitive to the environmental change 12 – 24 hours after landfall. A 6-hour lag is found between the environmental change and the movement of a TC after landfall.     

Northward Shift in Landfall Locations of Tropical Cyclones over the Western North Pacific during the Last Four Decades

This study analyzes landfall locations of tropical cyclones(TCs)over the western North Pacific during 1979–2018.Results demonstrate that the landfall locations of TCs over this region have shifted northward during the last four decades,primarily due to the shift of landfalling TC tracks,with the decreasing/increasing proportion of westward/northward TC tracks.In particular,the northward shift of the landfalling TCs was not related to their formation locations,which have not markedly changed,whereas"no-landed"TCs have significantly shifted northward.TC movement was significantly and positively correlated to the zonal component of the steering flow,while the correlation between TC movement and the meridional component of the steering flow was relatively unobvious.The westward steering flow in the tropical central Pacific that occurred around the formation and early development of the westward TCs was significantly weakened,which was unfavorable for their westward movement,thereby,causing the higher proportions of northward moving tracks.This weakened westward flow was related to the northward shift of the subtropical high ridge,which was caused by significant weakening of the southern part of the subtropical high.The vertical wind shear,sea surface temperature,and convective available potential energy also showed that the northern region of the western North Pacific became more favorable for TC development,whereas the upper divergence,low-layer relative vorticity,and accumulated water vapor content were not obviously related to the northward shift of TCs.     

1949—2019 年影响山东的热带气旋时空分布及极端降水和大气环流异常

使用中国气象局热带气旋资料中心的热带气旋最佳路径数据集和NCEP/NCAR再分析资料提供的月平均数据,对北上影响山东的热带气旋（tropical cyclone,TC）及其造成的极端降水进行统计分析,并揭示了有利于 TC北移影响山东的大气环流特征。结果表明：影响山东的 TC主要出现 于 6—9 月,其中盛夏时节（7、8 月）TC对山东影响最大;TC影响山东时,强度主要为台风及以下等 级,或已发生变性;TC会引发山东极端降水事件,TC极端降水多出现在夏秋季（7—9 月）,其中8月的占比最大,9月次之,TC降水在极端降水事件中的占比约为 10%,但年际变化大,有些年份占比达60%以上,特别是1990 年以来 TC对极端降水的贡献显著增强;影响山东的 TC主要生成于西 北太平洋,多为转向型路径;当500 hPa位势高度异常场呈太平洋一日本遥相关型的正位相时,TC更易北上影响山东,此时西北太平洋副热带高压位置偏北,其外围气流会引导TC北上转向,对华东地区造成影响;850 hPa上,南海至西北太平洋存在异常气旋式环流,对流活跃,夏季风环流和季风槽加强,有利于TC的生成和发展,同时,华东、华南上空有异常上升运动,涡度增大,垂直风切变减小,水汽充沛,TC登陆后强度能得到较好的维持。     

Impact of initial storm intensity and size on the simulation of tropical cyclone track and western Pacific subtropical high extent

Typhoon Megi, the 13th typhoon of the 2010 typhoon season, was selected for case study by utilizing the Weather Research and Forecasting (WRF) model. Twelve sensitivity experiments with various initial tropical cyclone (TC) intensities and sizes were conducted to investigate their impacts on the simulation of typhoon track. Interaction between TC and the western Pacific subtropical high (WPSH) was also analyzed to explore the mechanism for the impact on TC track of the initial TC intensity and size. Numerical results indicate that the simulated TC size and TC track are sensitive to initial TC intensity and size. Stronger initial TC intensity and larger initial TC size often lead to larger simulated TC size and make TC turn northward earlier. Further analysis suggests that, with the increase of initial TC intensity and size, more air mass enters into the TC region, which subsequently reduces the extent of WPSH. As a result, the steering flow changes significantly and eventually causes the TC to turn northward earlier. The present study confirms that the initial TC intensity and size have certain influences on the TC track simulation, which demonstrates the importance of accurate initial condition for successful simulation of the TC intensity and TC track. Moreover, it also deepens our understanding of the interaction between TC and WPSH, provides helpful clues for the TC track change study, and discusses the future directions for improvement of TC track forecast.     

Impact of Interannual Variation of Synoptic Disturbances on the Tracks and Landfalls of Tropical Cyclones over the Western North Pacific

This study investigates the tropical cyclone (TC) activity associated with the two leading modes of interannual variability in synoptic disturbances. Both leading modes are found to be related to a dipole pattern of TC occurrence between the subtropical western North Pacific and the South China Sea. Therefore, in this study we performed composite analyses on TC tracks and landfalls, based on the cases of combined modes, to highlight the differences. The composite results indicate that these cases are characterized by distinct features of TC tracks and landfalls: more TCs tend to take recurving tracks and attack eastern China, Korea and Japan, or more TCs exhibit straight-moving tracks and hit the Philippines, Vietnam and southern China. Further analyses suggest that these distinctions in the TC prevailing tracks and landfalls can be attributed to the differences in large-scale steering flow and TC genesis location.     

台风“鲇鱼”(1013)路径突变过程的成因分析

利用NCEP提供的GFS(Global Forecast System)再分析资料,对2010年西北太平洋最强台风“鲇鱼”(1013)路径突变的成因开展诊断分析,研究其影响系统、引导气流的演变特征等,并运用CPS(Cyclone Phase Space)方法对其生命史中的热力结构演变过程进行定量描述,重点分析路径突变前后各因子的变化。结果表明,“鲇鱼”移入南海后,冷空气南侵导致其热力结构发生变化,台风环流右侧较暖,此时引导气流微弱,“趋暖”运动占主导,首先引起路径向右偏转,随后引导气流转为西南气流并逐渐增强,在二者共同作用下,“鲇鱼”路径持续右转,逐渐向东北方向移动,完成路径突变。     

南海灾害性土台风统计分析

根据台风年鉴资料统计分析了南海热带气旋(指在南海海域生成的热带气旋、又称南海灾害性土台风、下面简称TC)，TC数量逐年逐月变化较大，除3月没有TC出现外，其余月份均有TC出现，年生成最多的TC为11个，最少的为1个，年平均6．2个，月生成最多的TC为5个，最少的为零个。TC登陆最多的是8月，12月至翌年4月没有TC登陆中国大陆，登陆范围主要在汕头至海南岛之间。TC的持久期一般均在4—7天，最长亦有19天。南海上生成的TC只有15％能够加强为台风，均集中在水深超过150米的海域。南海是TC发生频繁、数量较多的海域。     

2013年影响海南热带气旋异常偏多成因分析

利用1983-2013年热带气旋年鉴、NCEP/NCAR全球再分析格点资料及国家气候中心74项环流指数资料等,统计分析了近30a西太平洋以及影响海南的热带气旋特征,并对2013年西太平洋热带气旋偏多、秋台集中以及影响海南热带气旋偏多的异常特征从天气学等方面进行了分析。结果表明,副热带高压、夏季风、越赤道气流、海表温度及北半球极涡等环流系统异常,是形成2013年西太平洋热带气旋偏多的主要原因。南半球冷高压发展激发越赤道气流增强,引发赤道西风加强;副热带高压偏北偏弱,夏季风增强,副高南侧热带辐合带对流活跃;南海-西太平洋海表温度偏高;极涡偏弱偏西,经向环流偏弱,中纬度冷空气活动不频繁等。多条件共同作用,有利于西太平洋热带气旋的生成。另外,副高呈东西向分布,南海海表温度偏高使得南海及菲律宾以东生成的热带气旋易于向西移动影响海南。     

ON THE PROCESS OF SUMMER MONSOON ONSET OVER EAST ASIA

Using daily observational rainfall data covered 194 stations of China from 1961 to 1995 andNCEP model analyzed pentad precipitation data of global grid point from 1979 to 1997,thedistribution of onset date of rainy season over Asian area from spring to summer is studied in thispaper.The analyzed results show that there exist two stages of rainy season onset over East Asianregion from spring to summer rainy season onset accompanying subtropical monsoon and tropicalmonsoon respectively.The former rain belt is mainly formed by the convergence of cold air and therecurred southwesterly flow from western part of subtropical high and westerly flow from the so-called western trough of subtropical region occurring during winter to spring over South Asia.Thelatter is formed in the process of subtropical monsoon rain belt over inshore regions of South ChinaSea originally coming from south of Changjiang (Yangtze) River Basin advancing with northwardshift of subtropical high after the onset of tropical monsoon over South China Sea.The pre-floodrainy season over South China region then came into mature period and the second peak of rainfallappeared.Meiyu,the rainy season over Changjiang-Huaihe River Basin and North China thenformed consequently.The process of summer tropical monsoon onset over South China Sea in 1998is also discussed in this paper.It indicated that the monsoon during summer tropical monsoononset over South China Sea is the result of the westerly flow over middle part of South China Sea,which is from the new generated cyclone formed in north subtropical high entering into SouthChina Sea,converged with the tropical southwesterly flow recurred by the intensified cross-equatorial flow.