SST对黄海、渤海登陆热带气旋路径和强度的影响

利用中国气象局整编的1949~2003年的热带气旋资料和美国国家环境预报中心的海表温度(SST)最优插值资料,应用EOF分解和概率分析等方法,分析了黄海、渤海登陆热带气旋个例所处环境场中的海温的空间和时间分布规律,计算得到该类热带气旋在黄海、渤海区达到最大可能强度(MPI)的概率分布。结果显示,在黄海、渤海海区的较强的(>1℃)SST正距平中心和渤海北部海域的SST正距平区是黄海、渤海登陆TC出现北行路径必要条件。所有TC个例过程发生之前均有一个黄海、渤海关键区SST距平上升过程,只有30%的TC达到MPI一半,只有1%的TC可能达到MPI的4/5。     

Simulation of Typhoon Muifa using a mesoscale coupled atmosphere–ocean model

A mesoscale coupled atmosphere–ocean model has been developed based on the GRAPES(Global and Regional Assimilation and Prediction System) regional typhoon model(GRAPES_TYM) and ECOM-si(estuary, coast and ocean model(semi-implicit)). Coupling between the typhoon and ocean models was conducted by exchanging wind stress, heat, moisture fluxes, and sea surface temperatures(SSTs) using the coupler OASIS3.0. Numerical prediction experiments were run with and without coupling for the case of Typhoon Muifa in the western North Pacific. To investigate the impact of using more accurate SST information on the simulation of the track and the intensity of Typhoon Muifa, experiments were also conducted using increased SST resolution in the initial condition field of the control test. The results indicate that increasing SST resolution in the initial condition field somewhat improved the intensity forecast, and use of the coupled model improved the intensity forecast significantly, with mean absolute errors in maximum wind speed within 48 and 72 h reduced by 32% and 20%, respectively. Use of the coupled model also resulted in less pronounced over-prediction of the intensity of Typhoon Muifa by the GRAPES_TYM. Moreover, the effects of using the coupled model on the intensity varied throughout the different stages of the development of Muifa owing to changes in the oceanic mixed layer depth. The coupled model had pronounced effects during the later stage of Muifa but had no obvious effects during the earlier stage. The SSTs predicted by the coupled model decreased by about 5–6°C at most after the typhoon passed, in agreement with satellite data. Furthermore, based on analysis on the sea surface heat flux, wet static energy of the boundary layer, atmospheric temperature, and precipitation forecasted by the coupled model and the control test, the simulation results of this coupled atmosphere–ocean model can be considered to reasonably reflect the primary mechanisms underlying the interactions between tropical cyclones and oceans.     

热带气旋进入北部湾后强度增强的环流特征分析

利用NCEP/NCAR再分析资料,对1949年以来7个进入北部湾后强度突然增强的热带气旋(TC)环流背景特征及物理量场特征进行分析,结果表明,有利TC进入北部湾后强度增强的环流背景是:(1)西太平洋副热带高压稳定加强西伸,(2)热带辐合带北抬至华南沿海活动,(3)西南季风爆发处于活跃期,(4)东风波西移叠加,(5)有适度的弱冷空气侵入;对物理量场的合成分析表明,TC进入北部湾前和进入北部湾后,环流中心附近500hPa涡度变化极小,200hPa高空散度增大,500hPa垂直上升速度增大,850hPa中南半岛水汽输送量增大。     

2016年西北太平洋和南海热带气旋预报精度评定

以中国气象局上海台风研究所整编的最佳路径数据集为依据,对2016年西北太平洋和南海热带气旋（TC）定位精度及路径、强度和登陆点预报精度进行了评定,结果表明：2016年定位总平均误差24.9 km,比2015年略偏大。主观和客观路径预报误差没有延续之前持续减小的趋势,整体预报能力比前两年略有降低。ECMWF EPS、NCEP GEFS和UKMO EPS三个集合预报系统的台风路径预报整体性能要好于其他集合预报系统。各主客观预报方法的台风强度预报性能与往年相比没有大的改进。主观方法对超强台风莎莉嘉在海南万宁的24 h登陆点预报误差均非常小,误差在15 km以下。全球模式的登陆点预报性能表现要优于区域模式。     

台湾岛及邻近区域热带气旋异常路径特征分析

利用热带气旋资料和天气图、卫星云图等观测资料,统计分析了1949-2008年入侵台湾岛及邻近区域的热带气旋出现的各类异常路径的时间、空间分布规律及成因。结果表明,异常路径的形成是环境流场和台湾地形共同作用的结果,在特定的环流形势下,台湾地形的影响,导致入侵这一带区域的热带气旋结构及其周围的气压场和流场发生变化,并可能诱生出地形槽或低压。热带气旋出现左折、右折、打转和诱生低压发展取代原热带气旋的异常路径,发生在不同地点的异常路径,地形和环境作用的主次关系不同。     

热带气旋生成过程的中尺度涡旋活动数值模拟

热带气旋生成过程中包含不同尺度环流及其相互作用。为此,本文将热带气旋生成数值模拟的起点提前到模拟中尺度涡旋(MCV)的生成,从而利用高分辨率数值试验结果,对热带气旋过程中的不同尺度涡旋活动进行分析。模式首先模拟了季风涡旋的东南侧增强的西南气流中出现低形变旋转性扰动,随着扰动的旋转性增强,中层出现水平尺度为200 km左右的MCV。在扰动区内的不同高度上还发现10~20 km尺度不等的中γ气旋性涡旋扰动,其中部分涡旋扰动具有热塔的特征,中γ气旋性涡旋扰动在MCV的旋转环境内不断组织化,低层气旋性涡旋扰动的分布比中层更加集中。模拟表明这些较小尺度的气旋性中尺度涡旋扰动对热带气旋的生成有重要作用。     

CWRF对中国近海热带气旋活动季节和年际变化及环境场影响的模拟

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,...     

An Application of the Adjoint Method to a Statistical-Dynamical Tropical-Cyclone Prediction Model （SD-90） Ⅱ： Real Tropical Cyclone Cases

In the first paper in this series, a variational data assimilation of ideal tropical cyclone （TC） tracks was performed for the statistical-dynamical prediction model SD-90 by the adjoint method, and a prediction of TC tracks was made with good accuracy for tracks containing no sharp turns. In the present paper, the cases of real TC tracks are studied. Due to the complexity of TC motion, attention is paid to the diagnostic research of TC motion. First, five TC tracks are studied. Using the data of each entire TC track, by the adjoint method, five TC tracks are fitted well, and the forces acting on the TCs are retrieved. For a given TC, the distribution of the resultant of the retrieved force and Coriolis force well matches the corresponding TC track, i.e., when a TC turns, the resultant of the retrieved force and Coriolis force acts as a centripetal force, which means that the TC indeed moves like a particle; in particular, for TC 9911, the clockwise looping motion is also fitted well. And the distribution of the resultant appears to be periodic in some cases. Then, the present method is carried out for a portion of the track data for TC 9804, which indicates that when the amount of data for a TC track is sufficient, the algorithm is stable. And finally, the same algorithm is implemented for TCs with a double-eyewall structure, namely Bilis （2000） and Winnie （1997）, and the results prove the applicability of the algorithm to TCs with complicated mesoscale structures if the TC track data are obtained every three hours.     

两类El Niño型对西北太平洋季风槽及热带气旋生成的可能影响

通过对1948~2015年不同El Ni?o事件下西北太平洋季风槽变化和热带气旋(tropical cyclone,TC)生成进行分析,初步探讨了不同El Ni?o型事件对季风槽及其对TC的可能影响。分析结果表明,较东太平洋增暖(eastern Pacific warming,EPW)年,中太平洋增暖(central Pacific warming,CPW)年季风槽偏弱,位置相对偏西、偏北。在CPW年,中(西和东)太平洋海温增暖(降低)引起了从中到西太平洋热带地区的西风异常和中太平洋地区上升运动及对流活动加强,使得季风槽加强东伸,同时西太平洋副高偏弱、偏北,季风槽向北推进;而在EPW年,赤道东(西)太平洋海温增暖(降低)使得赤道地区西风异常显著加强东扩,异常Walker环流的上升支东移至东太平洋,季风活动加强,副高偏强、偏南,这使得季风槽较CPW年相比更强、更偏东。利于TC生成的大尺度环境因子随季风槽强度和位置的变化而发生改变,在CPW年,低层气旋性涡度、高层辐散、高的中层相对湿度以及低垂直风切变区随着季风槽向北移动;而在EPW年,这些因子随季风槽向南、向东偏移。这些大尺度环境因子的变化使得西北太平洋TC生成的位置在CPW年比EPW年更加偏北、偏西。     

2009年西北太平洋热带气旋定位和业务预报精度评定

依据《台风业务和服务规定》分析2009年热带气旋(TC)业务定位和业务预报精度,主要包括:6个方法的定位精度,12个综合预报方法、3个客观预报方法和6个数值预报方法的路径预报精度,以及4个方法的强度(近中心最大风速,下同)预报精度评定。结果表明:各方法的平均定位误差均小于21 km,平均17.1 km,较2008年有所改进。国内综合预报方法的24小时、48小时和72小时路径预报的平均距离误差分别为115.8 km、217.5 km和357.1 km,与2008年相比有所偏大;客观预报方法略优于综合预报方法,24小时和48小时预报的平均距离误差分别为113.0 km和211.4 km;4个官方综合预报方法比较发现,中央气象台对我国近海海域的TC路径预报具有明显优势。强度预报仍然以统计方法为主,2009年24小时和48小时近中心最大风速预报的平均误差分别为4.90 m·s~(-1)和7.43 m·s~(-1),相比近10年的平均水平,预报性能没有明显提高。