中国东南地区热带气旋大风及其伴随天气的统计特征

利用2010～2016年中国地面站重要天气报文、中国气象局（CMA）热带气旋最佳路径数据集以及地面站逐小时降水资料，对热带气旋（TC）影响下我国东南地区地面大风及其伴随天气特征进行统计分析，结果表明：（1）该区域TC大风主要沿海岸线分布，至内陆频次递减；TC大风多以东北风向为主，登陆前大风站点居多，12级以上的强风速基本分布在距TC中心300 km范围内。（2）强热带风暴（STS）和台风（TY）强度TC引起的站点大风最多，但16级以上大风主要出现在强台风（STY）和超强台风（Super TY）强度等级。慢速TC引起的站点大风主要出现其移向右前侧，快速主要出现在其右后侧。TC大风中向岸风均值略大于离岸风，其中12级以上风速向岸风站点多于离岸风，但16级以上大风则是离岸风站点明显多于向岸风。（3）约89.8%的TC大风伴随降水，分布于TC中心附近，东北风为主，峰值出现在8月。约10.2%的TC大风无降水，主要分布在TC外围，北风和东南风为主，风速较弱，多出现于5月和12月。12级以上TC大风几乎均伴随着降水，而无降水TC大风风速达12级以上样本很少。（4）约23.8%的TC大风伴随强对流天...     

登陆的0915号热带气旋“巨爵”降水分布及其中尺度结构的分析

利用自动气象站、雷达和TRMM卫星的观测资料,对2009年广东登陆热带气旋(TC)“巨爵”(0915)的降水分布进行了分析。结果表明:登陆TC“巨爵”的降水具有明显的非对称性和中尺度特征,TC降水主要位于移动路径的左侧。通过对海表温度(SST)、水汽通量、Q矢量和环境风垂直切变等分析发现,SST分布、水汽辐合、低层对流上升运动和垂直切变都有利于在TC移动路径的左侧产生降水。通过Barnes带通滤波对中尺度结构进行分离发现,登陆TC“巨爵”的降水存在明显的围绕TC中心的中尺度螺旋结构,呈带状或块状形式;登陆TC“巨爵”的局地强降水主要与中尺度螺旋结构的降水有关。      

Winnie(9711)台风变性加强过程中的降水变化研究

热带气旋变性过程是其结构、强度及其风雨分布发生显著变化的过程,常导致预报失败。基于T106格点分析资料、日本气象厅TBB资料以及MM5V3数值模式结果,对9711号台风Winnie变性加强过程中的降水变化特征及其机理进行研究。结果表明,Winnie台风变性加强过程中降水分布非对称性明显,强降水带首先出现在台风环流北部,之后向南弯曲,其强降水中心绕台风中心从北部顺时针转向东北和东南部。这种降水变化一方面与Winnie与西风带高空槽相互作用过程中环境风垂直切变明显增大,且其指向顺时针旋转有关。此间台风垂直结构发生明显倾斜,变性前期涡旋环流随高度增加先向北倾斜,发展到最强时又趋于垂直,之后又向东南倾斜。强降水区出现在垂直切变的下风方、台风气柱倾斜方向一侧。另一方面还与台风环流内冷、暖平流活动紧密相关,强降水落区与低层暖平流输送位置关系密切。对流涡度矢量垂直分量反映了Winnie台风环流内中尺度锋区与风垂直切变的相互作用,800 hPa上的大值区对其强降水落区有较好的指示意义。     

登陆海南的热带气旋中尺度降水分布变化特征

利用每小时地面观测资料和卫星资料,以1996-2005年在海南岛登陆的热带气旋为研究对象,按照气旋移动路径将其分为4大类,从4类不同路径的7个个例分析揭示了登陆海南热带气旋降水的中尺度特征及其分布变化.结果表明,不同路径的热带气旋登陆前10个小时之内,中尺度强降水基本上分布于热带气旋中心附近;而热带气旋登陆后,中尺度强降水开始出现明显的"离心"或"偏心"特征.不同路径的热带气旋在登陆前后,其最大降水中心的强度变化也有明显差异.登陆前后,中尺度强降水基本均出现在气旋中心西南到东南侧100～200km内,表现出明显的南北不对称.个例分析也证明,热带气旋强降水在空间和时间上都具有明显的中尺度特征.     

华东登陆热带气旋降水不同分布的对比分析

利用CMORPH降水资料，将热带气旋（TC）登陆后的降水分为路径左侧降水（L型）和右侧降水（R型）两类，并针对登陆华东地区TC的 L型和R型降水的大气环流场、环境水平风垂直切变以及台风环流内的动热力条件进行对比分析，结果表明:2005～2014年间登陆华东地区的20例TC中包括12例L型和8例R型。总体来看，大气环流因子对于登陆华东TC降水分布起主要作用。L型降水TC高层南亚高压主要呈纬向带状分布，在登陆过程中路径左侧维持偏东风高空辐散气流，中层西风槽偏东，西太平洋副热带高压（简称副高）偏南，环境水平风垂直切变指向西南。R型降水TC高层南亚高压断裂，呈经向分布。TC路径左侧风场较均匀，右侧东南风高空辐散气流明显。副高的位置偏北呈块状，同时环境水平风垂直切变指向东北，有利于路径右侧降水。台风环流内，低层冷暖平流输送以及水汽辐合与降水落区也有较好对应关系。L型TC低层暖平流的输送使TC西南象限低层增暖，大气稳定度降低。同时水汽辐合区也主要位于西南象限，有利于TC路径左侧降水。而R型TC副高位置偏北可将南侧的东南暖湿气流向台风环流更西部输送，东北象限维持暖平流，有利于路径右侧降水发生。     

1306号热带气旋“温比亚”非对称降水的环境场特征

利用常规气象观测资料、NCEP1°×1°逐6h全球格点资料以及区域自动站降水资料、FY-2E卫星云图与多普勒天气雷达拼图资料,分析2013年第6号热带气旋(TC)"温比亚"在广西造成的非对称降水的环境场特征。结果表明,受副热带高压西南侧稳定而深厚的东南气流引导,"温比亚"西北行深入到广西中部,有利于广西出现较大范围暴雨。200hPa上TC流出气流的中心偏于其中心的南侧,为降水不对称分布提供了动力背景;TC风场分布明显不对称,导致涡度、散度动力场结构呈不对称分布;低层辐合区主要分布在TC中心南侧,整层水汽通量辐合中心位于TC中心南侧,从而使暴雨集中在TC中心南侧。环境风垂直切变矢量指向TC移动路径的左侧,有利于TC移动路径左侧出现强的对流及降水,结合水汽辐合条件,可将其作为TC暴雨落区预报的一个判据。相对湿度(RH)呈均匀分布,假相当位温(θse)呈准对称分布,表明TC降水的非对称分布主要由动力因子而非热力因子引起。     

基于MTCSWA风场资料对西北太平洋热带气旋风场结构的气候统计特征研究

基于多平台热带气旋表面风场资料（MTCSWA）,研究了2007～2016年6～11月西北太平洋上不同尺度热带气旋（TC）的气候统计特征,TC各级风圈半径在不同象限的变化特征、风场结构的对称度及二者与强度变化之间的相关性。利用7级风圈半径与TC近中心最大持续风速（MSW）来定义TC的尺度和强度。结果表明,西北太平洋上TC的平均尺度为221.9 km,其中小TC平均尺度为96.4 km,大TC平均尺度为346.4 km。大TC活动位置的空间分布较小TC更为集中,整体活动范围较小TC偏北。TC尺度的峰值出现在8月和10月。在TC的风场结构中,7级、10级、12级风圈的平均半径分别为221.9、121.0、77.4 km。TC风圈的对称度的统计结果表明7级风圈的对称度最低,12级风圈的对称度最高。相关分析表明,在TC的生命史中,各级风圈半径与其强度存在一定的正相关关系,其中12级风圈半径与强度的相关性最低;对于同一风圈而言,在TC的不同发展阶段中,不同象限的风圈半径与强度的相关性不同。在TC的风场结构中,风圈的对称度与TC强度的相关性随着风圈强度的增强而减弱,只有7级风圈的对称度在TC的整个生命周期中表现出与TC强度之间的弱的正相关关系。     

台风“莫拉非”非对称环流与强度变化的关系

利用热带气旋定位资料和NCEP同化资料,通过动态合成方法分析0906号台风"莫拉非"的非对称环流特征,探讨非对称环流与"莫拉非"强度变化的联系。结果表明:"莫拉非"的环境风场水平切变以对流层低层经向风水平切变最显著,且超前于"莫拉非"的强度变化;热带气旋中心附近-6~6m.s-1的纬向风垂直切变密集带和北侧东风切变的南移,是"莫拉非"逐渐增强的有利条件;"莫拉非"中心附近存在高低层相对涡度垂直切变正值中心,其在热带气旋发展成台风时达到极大值。     

西北太平洋环境风垂直切变和热带气旋移动对涡旋内对流非对称分布影响的特征分析

热带气旋（TC）预报特别是强度预报是当今大气科学研究和业务预报的重点、难点问题,TC环流内部的对流系统对气旋的结构和强度变化有着十分重要的影响。利用FY-2C/2E黑体亮温（TBB）资料和NCEP分析资料,研究了2005-2012年西北太平洋热带气旋外雨带区的对流非对称分布特征,及其与环境风垂直切变和TC移动的关系。分析发现,整层风垂直切变的方向与TBB一波非对称大值区关于方位角的分布有很好的对应关系。在弱整层风垂直切变条件下（<5 m/s）,TC移动引起的非对称摩擦效应会使对流易出现在移动方向的右前象限。在中强整层风垂直切变条件下（>5 m/s）,风切变成为影响对流非对称分布的主要因子,TC外螺旋雨带区的对流集中于顺风切方向及其左侧,对流偏离顺切变左侧的程度一方面受到TC内逆时针环流的影响,另一方面与风垂直切变的强度有关：对于发展阶段的TC,当风垂直切变增强时,一波非对称分布更加显著,切变越强,TC强度越大,外雨带区的对流越偏离顺风切左侧;对于消亡阶段的TC,风垂直切变的影响作用并不明显。     

高空槽脊对台风“天兔”（0705）变性过程中非对称降水的影响

本文基于NCEP再分析资料、TRMM卫星降水资料和RSMC最佳路径集（Best-track Dataset）资料,分析了热带气旋（TC）“天兔”变性过程中降水分布和大尺度环流的演变,并结合片段位涡反演进行修改槽脊的数值试验,研究了环流调整对TC变性过程中非对称降水的影响。结果表明:（1）“天兔”变性前降水集中在路径左侧,伴随着纬向型向经向型调整的背景环流,副热带高压南退的同时减弱西进;（2）TC降水的非对称分布与冷暖锋的相对强弱、水汽输送情况以及高空冷空气下传的落区有直接关系;（3）加强环流调整后,系统斜压性加强,与LOT（降水集中于TC路径左侧）型降水相关的环流指数增大过程随之加强,有利于LOT型降水分布进一步加强。     

Effects of vertical wind shear and storm motion on tropical cyclone rainfall asymmetries over the North Indian Ocean

Tropical cyclone (TC) rainfall asymmetry is often influenced by vertical wind shear and storm motion. This study examined the effects of environmental vertical wind shear (200-850 hPa) and storm motion on TC rainfall asymmetry over the North Indian Ocean (NIO): the Bay of Bengal (BoB) and the Arabian Sea (AS). Four TC groups were used in this study: Cyclonic Storm (CS), Severe Cyclonic Storm (SCS), Very Severe Cyclonic Storm (VSCS) and Extreme Severe Cyclonic Storm (ESCS). The Fourier coefficients for wave number-1 was used to analyze the structure of TC rainfall asymmetry. Results show that the maximum TC rainfall asymmetry was predominantly in the downshear left quadrant in the BoB, while it placed to downshear right quadrant in the AS, likely due to the different primary circulation strength of the TC vortex. For the most intense cyclone (ESCS), the maximum TC rainfall asymmetry was in the upshear left quadrant in the BoB, whereas it was downshear right quadrant in the AS. It is evident for both basins that the magnitude of TC rainfall asymmetry declined (increased) with TC intensity (shear strength). This study also examined the collective effects of vertical wind shear and storm motion on TC rainfall asymmetry. Here, the analysis in case of the strong shear environment (>7 m s^-1) omitted for the AS because the maximum value for this basin was about 7 m s^-1. The result showed that the downshear left quadrant was dominant in the BoB for the maximum TC rainfall asymmetry. In a weak shear environment (<5 m s^-1), on the other hand, downshear right quadrant is evident for the maximum TC rainfall asymmetry in the BoB, while it placed dominantly downshear left quadrant in the AS. In the case of motion-relative wavenumber-1, the maximum TC rainfall asymmetry was dominantly downshear for both basins.     

A COMPOSITE STUDY OF RAINFALL ASYMMETRY OF TROPICAL CYCLONES AFTER MAKING LANDFALL IN GUANGDONG PROVINCE

Based on observed rainfall data, this study makes a composite analysis of rainfall asymmetry in tropical cyclones(TCs) after making landfall in Guangdong province(GD) during 1998—2015. There are 3.0 TCs per year on average making landfall in GD and west of GD(WGD) has the most landfall TCs. Most of TCs make landfall in June,July, August, and September at the intensities of TY, STS, and TS. On average, there is more rainfall in the southwest quadrant of TC in CGD(center of GD), WGD, and GD as a whole, and the maximum rainfall is located in the southwest near the TC center. The mean TC rainfall in the east of GD(EGD) leans to the eastern side of TC. The TC rainfall distributions in June, July, August, and September all lean to the southwest quadrant and the maximum rainfall is located in the southwest near the TC center. The same features are found in the mean rainfall of TD, TS, STS, TY,and STY. The maximum rainfall is mainly in the downshear of vertical wind shear. Vertical wind shear is probably the dominate factor that determines asymmetric rainfall distribution of TCs in GD. Storm motion has little connection with TC rainfall asymmetry in GD.     

AN OBSERVATIONAL STUDY ON DISTRIBUTION OF PRECIPITATION ASSOCIATED WITH LANDFALLING TROPICAL CYCLONES AFFECTING CHINA

In order to provide an operational reference for tropical cyclone precipitation forecast,this study investigates the spatial distributions of precipitation associated with landfalling tropical cyclones(TCs) affecting China using Geostationary Meteorological Satellite 5(GMS5)-TBB dataset.All named TCs formed over the western North Pacific that made direct landfall over China during the period 2001-2009 are included in this study.Based on the GMS5-TBB data,this paper reveals that in general there are four types of distribution of precipitation related to landfalling TCs affecting China.(a) the South-West Type in which there is a precipitation maximum to the southwestern quadrant of TC;(b) the Symmetrical South Type in which the rainfall is more pronounced to the south side of TC in the inner core while there is a symmetrical rainfall distribution in the outer band region;(c) the South Type,in which the rainfall maxima is more pronounced to the south of TC;and(d) the North Type,in which the rainfall maxima is more pronounced to the north of TC.Analyses of the relationship between precipitation distributions and intensity of landfalling TCs show that for intensifying TCs,both the maximum and the coverage area of the precipitation in TCs increase with the increase of TC intensity over northern Jiangsu province and southern Taiwan Strait,while decreasing over Beibu Gulf and the sea area of Changjiang River estuary.For all TCs,the center of the torrential rain in TC shifts toward the TC center as the intensity of TC increases.This finding is consistent with many previous studies.The possible influences of storm motion and vertical wind shear on the observed precipitation asymmetries are also examined.Results show that the environmental vertical wind shear is an important factor contributing to the large downshear rainfall asymmetry,especially when a TC makes landfall on the south and east China coasts.These results are also consistent with previous observational and numerical studies.     

ANALYSIS OF RAINSTORMS ASSOCIATED WITH SIMILAR TRACK TROPICAL CYCLONES HAITANG (0505) AND BILLS (0604)

It is generally thought that the influence of comparable track typhoons is approximately similar,but in fact their wind and especially their rainstorm distribution are often very different. Therefore,a contrastive analysis of rainstorms by tropical cyclones (TCs) Haitang (0505) and Bilis (0604),which are of a similar track,is designed to help understand the mechanism of the TC rainstorm and to improve forecasting skills. The daily rainthll of TC itaitang (0505) and Bills (0604) is diagnosed and compared.The result indicates that these two TCs have similar precipitation distribution before landtall but different precipitation characteristics after landthll. Using NCEP/GFS analysis data,the synoptic situation is analyzed; water vapor transportation is discussed regarding the calculated water vapor flux and divergence.The results show that the heavy rainfall in the Zhejiang and Fujian Provinces associated with Haitang (0505) and Bitis (0604) before landlhll results ti'om a peripheral easterly wind,a combination of the tropical cyclone and the terrain. After landthll and moving far inland of the storm,the precipitation of Haitang is caused by water vapor convergence carried by its own circulation; it is much weaker than that in the coastal area. One of the important contributing thctors to heavy rainstorms in southeast Zhejiang is a southeast jet stream,which is maintained over the southeast coast. In contrast,the South China Sea monsoon circulation transports large amounts of water vapor into Bills - when a water-vapor transport belt south of the tropical cyclone significantly strengthens - which strengthens the transport. Then,it causes water vapor flux to converge on the south side of Bilis and diverge on the north side. Precipitation is much stronger on the south side than that on the north side. After Bilis travels far inland,the cold air guided by a north trough travels into the TC and remarkably enhances precipitation. In summary,combining vertical wind shear with water vapor transportation is a good way to predict rainstorms associated with landing tropical cyclones.     

相似路径热带气旋“海棠”(0505)和“碧利斯”(0604)暴雨对比分析

一般认为相似路径台风的影响大致相似,但实际上相似路径台风的风雨分布尤其是暴雨分布往往有很大差异,因此,对相似路径热带气旋“海棠”(0505)和“碧利斯”(0604)暴雨成因的对比分析有助于加强台风暴雨发生机制的认识和预报。“海棠”(0505)和“碧利斯”(0604)逐日降水分布对比分析表明,两者登陆前降水分布类似,而登陆后降水分布差异比较大。利用NCEP/GFS 1 °×1 °分析资料对热带气旋登陆前后天气形势、水汽通量和水汽通量散度进行诊断分析,结果表明：“海棠”(0505)和“碧利斯”(0604)登陆前引起浙闽沿海地区大降水主要是热带气旋外围偏东气流和地形共同影响下形成。“海棠”登陆后,维持在浙江东部沿海东南风急流不断输送水汽到“海棠”倒槽内引起浙东南沿海强降水,深入内陆后,降水主要由“海棠”自身环流携带的水汽辐合引起的,降水比沿海地区明显减弱;而“碧利斯”登陆后,有明显的南海季风环流输送水汽并入热带气旋南侧环流,在其南侧形成偏南风急流,使南侧水汽输送得到明显加强,造成“碧利斯”南侧水汽通量辐合,北侧水汽通量辐散,南侧降水比北侧降水强很多;深入内陆后,“碧利斯”环流仍维持并引导北方槽后弱冷空气渗透到其西南侧,使南侧降水进一步增幅。本文还探讨了包括热带气旋外核在内区域平均垂直风切变和热带气旋强降水落区的关系,结果表明：“海棠”和“碧丽斯”大暴雨落区均对应于暴雨区区域平均垂直风切矢量左侧水汽通量散度负值区。“海棠”垂直风切变矢量平行于移动路径并指向移动路径后方是造成“海棠”强降水分布在其移动路径右侧的重要原因,“碧利斯”垂直风切变矢量平行于移动路径并指向移动路径前方是造成“碧利斯”强降水分布在其移动路径左侧的重要原因。因此,利用垂直风切结合水汽输送条件可以作热带气旋大暴雨落区预报可能是一种比较有效的方法。     

Tropical cyclones in the SW Indian Ocean. Part 2: structure and impacts at the event scale

The southwest Indian Ocean (5°–20°S, 45°–70°E) experiences frequent tropical cyclones (TC) in the December–March season. In this paper, TC composite and case-study structure and impacts are studied using daily oceanic and atmospheric fields from model-reanalyzed data, satellite remote sensing, and in situ station data. The TC environment is characterized according to mean track: W-, SW-, and S-moving. Case studies of TC are investigated, and impacts such as storm surge and rainfall are evaluated through comparison of ‘real’ and ‘model’ datasets in the period since 1998. The northern sub-tropical jet stream is found to influence the intensity and track of TC in the SWIO. The composite SW-moving TC maintains intensity compared to the other tracks, which decline in strength. Variability is found in TC rainfall distribution, with maximum intensity in a spiral band 1–2 days before peak intensity, based on satellite estimates. There is a re-establishment of equatorial rainfall in the case of southward moving TC after peak intensity. The W-moving TC lacks monsoon inflow compared to the recurving TC. Comparisons are made between low-resolution model-estimated rainfall, various satellite products, and station-observed rainfall. TC spiral rain-band intensity is found to be similar to that reported elsewhere in the tropics, based on a limited sample of TRMM PR data and station reports. The satellite-derived daily rainfall out-performs NCEP reanalysis due to low resolution and underestimated diabatic heating. Similarly, the circulation within a 300-km radius of the composite TC is poorly resolved by re-analysis; winds, swells, and storm surges are too low by a factor of two compared with QuikSCAT and in situ measurements. This work will offer ways to adjust operational forecasts of winds, rainfall, and swells around tropical cyclones, so that TC risk and impacts are better managed.     

IMPACTS OF TWO TROPICAL CYCLONES EXPERIENCING EXTRATROPICAL TRANSITION DURING NORTHWARD PROGRESSION ON THE RAINFALL OF LIAODONG PENINSULA

Both of Typhoon Winnie (9711) and Matsa (0509) underwent an extratropical transition (ET) process when they moved northward after landfall and affected Liaodong Peninsula. However, Matsa produced half as much rainfall as Winnie, although it struck Liaodong Peninsula directly while Winnie passed through the Bohai Sea. The relations between the ET processes and the precipitation over Liaodong Peninsula are examined. The result shows that the precipitation difference between Winnie and Matsa was closely related to the interactions between the westerly systems and typhoons during their ET processes. Winnie was captured by the upper westerly trough and then coupled with it when moving to the mid-latitudes, and the positive anomaly of moist potential vorticity (MPV) was transported downward from the upper troposphere over the remnant circulation of the tropical cyclone (TC). It was favorable to the interaction between tropical warm and wet air and westerly cold air, causing convective cloud clusters to form and develop. The rain belt composed of several meso-β cloud clusters over the Liaodong Peninsula, resulting in heavy rainfall. On the other hand, Matsa did not couple with any upper trough during its ET process and the positive anomaly of MPV in the upper troposphere and its downward transfer were weak. Only one meso-β cloud cluster occurred in Matsa’s rain belt during its ET process that tended to lessen rainfall over Liaodong Peninsula.