台风“海高斯”和“天鸽”快速加强成因的对比分析

利用欧洲中心ERA-Interim逐6 h再分析资料和国家气象中心提供的逐小时台风业务资料,对比分析了2020年第7号台风“海高斯”和2017年第13号台风“天鸽”的环流形势和强度结构特征,发现二者的尺度都比较小;生成的时间和移动路径比较相似;并且都出现了近海快速加强的过程。从对比分析来看,造成两个台风近海快速加强的共同原因主要有海温异常偏高、环境风的垂直切变较小以及有利的高低层环流配置等,而造成两个台风近海快速加强的不同原因也较为显著,分别从位涡垂直分布、涡度收支和涡度拟能等方面进行诊断分析,得到一些有利于台风强度快速增长的不同因素。     

气旋爆发性发展过程的动力特征及能量学研究

本文对不同路径的爆发性气旋进行了动力特征及能量学研究。发现高空大值位涡空气的下伸是气旋爆发性发展的一个重要条件。初生气旋逐渐向强位涡区移近并形成上下位涡区相接的形势。使气旋迅速发展。高空急流与气旋发展有密切关系。发展中的气旋明显地向着急流左侧的辐散区移动。急流的突然加强及高空强风动量的不断下传，构成了下层的强风带及上下一致的急流结构。能量学研究指出在气旋发展前气旋内散度风动能向旋转风动能的转换突然增强。散度风动能在爆发气旋发展时有明显增长。     

“莫拉克”台风暴雨过程中湿位涡场的演变特征

利用NCEP/NCAR 1°×1°再分析资料,计算了2009年第8号台风“莫拉克”引发浙江沿海地区强降水过程的湿位涡(MPV)和假相当位温(θse),重点分析了正压项(MPV1)和斜压项(MPV2)的正负值变化特征.结果表明,通过判断大气对流不稳定处,θse陡立面密集区,能量锋较强区域,同时结合上升运动,可以作为判断强...     

2007号台风“海高斯”快速加强的成因分析

利用欧洲中期天气预报中心(European Center for Medium-Range Weather Forecasts,ECMWF)ERA-Interim逐6 h再分析数据(水平分辨率0.25°×0.25°)和国家气象中心提供的逐小时台风业务数据,分析了2020年第7号台风“海高斯”的路径和强度特征,并在此基础上分析其出现快速加强的原因。结果表明:1)“海高斯”个头小、海温异常偏高、风的垂直切变较小是其出现快速加强的有利因素;2)高空冷涡是“海高斯”后期高空北向出流打开的有利条件;3)来自副热带高压南侧的东向气流对“海高斯”水汽和涡度的输送也是其出现快速加强的有利条件。     

西北太平洋热带气旋快速加强过程中的水汽特征分析

利用NCEP的1°(纬度)×1°(经度)全球最终分析资料和JTWC(Joint Typhoon Warning Center)最佳路径资料,对2002~2011年西北太平洋热带气旋(TC)非减弱阶段快速加强(Rapid Intensification,RI)和缓慢加强及强度稳定(Non-RI)过程中,TC环境场及其内部各区域水汽分布和输送特征进行统计分析,揭示水汽因子对TC随后24 h强度变化的影响,为TC强度突变的趋势预报提供依据。结果表明:对流层低层900 h Pa层半径3~10纬距区域平均相对湿度(RH_3-10)能明显区分RI与Non-RI过程,说明西北太平洋TC强度变化对水汽的敏感高度较大西洋更接近洋面;RI初始时刻的RH_3-10显著大于Non-RI,而水平水汽通量(F_all)则弱于Non-RI,说明RI开始时刻TC环境表现为高水汽含量和较小的水汽输送,而随着RI过程TC内强对流发展对水汽的消耗,水汽含量明显减小故水汽通量则出现增强;RI和Non-RI过程水汽因子的分布和输送在TC内核区和外雨带差异明显,初始时刻RI过程净水汽获得区域大于Non-RI。相关性分析同样表明,适宜的相对湿度和水汽通量是非减弱阶段RI的有效潜势预报因子。     

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。     

南亚高压南部环境位涡对台风加强的影响分析

利用2002—2009年8年中6、7、8、9月的NCEP 1 °×1 °再分析资料对登陆我国大陆的台风与150 hPa高层位涡的关系进行统计,8年中共有23个台风受到150 hPa南亚高压南部边缘位涡的影响。其中3个台风(0216“森拉克”、0604“碧利斯”、0903“莲花”),在其发展初期在南亚高压南部的大值环境位涡进入台风中心后,台风中心气压下降。通过诊断分析从等值线的角度得出高层位涡与此类台风发展的关系,在150 hPa高层正位涡异常的作用下,等熵面向大值位涡处汇聚,这种形式可使正位涡异常区两侧的等熵面向下倾斜,从而引起台风中高层的暖中心加强以及中层位涡增大,中层的位涡增大以及暖中心的出现又有利于低层气旋性涡度增长,导致台风中心气压下降,使台风强度增强。根据吴国雄的倾斜涡度发展(SVD)理论,其原因可能是等熵面倾斜使垂直涡度发展,从而加强对流运动潜热释放使台风暖心加强,使得台风的强度加强。通过位涡反演试验也证实了高层位涡对中层位涡发展的影响大于低层。      

气旋快速发展过程中潜热释放重要性的位涡反演诊断

本文分析了一次爆发性气旋过程中的位涡演变特征,揭示了凝结潜热释放对气旋人上工位涡柱形成所起的作用;通过数值求解位涡反演诊断方程定量诊断出气旋爆发性发展阶段,凝结潜热释放对低层降压和气旋式环流增强的重要影响。     

环境场对西北太平洋热带气旋快速增强过程的影响

利用美国联合台风预警中心整编的西北太平洋1970—2012年热带气旋(TC)最佳路径数据集及ERA-Interim再分析资料,利用极端天气法确定TC快速增强(RI)的阈值为30 kn,分析了快速增强(RI)TC的时空分布特征;从RI的样本中选取9个个例,采用动态合成分析法,对TCRI过程的环境场进行比分析。研究表明:(1)菲律宾群岛以东(10~15°N,130°E)海域为RI发生频数最多的区域,南海地区发生RI的情况明显偏少。(2)RI在1972年发生的概率最大,而在2005年发生的概率最小,1997年后,RI发生的概率波动性较大。(3)西风与西南风水汽输送结合150h Pa附近的反气旋强辐散作用,有利于TCRI过程的进行。(4)RI发生前24 h至RI发生后的6 h,TC中心附近区域平均东风切变较快增大,其值由0.5 m·s~(-1)增加到2.5 m·s~(-1)左右,之后保持在2.0~3.0 m·s~(-1),使TC处于一个有利于其RI过程的纬向风切变环境。     

台风“山竹”（1822）引发华南暴雨过程机制分析

利用NCEP/NCAR 1°×1°的FNL再分析资料、CMORPH（CPC MORPHing technique）卫星-地面自动站融合降水数据以及FY-2G卫星反演的TBB（black-body temperature,云顶亮温）对1822号台风“山竹”在华南造成强降水过程进行了分析。结果表明：西北太平洋副热带高压和南亚高压的稳定维持有利于台风残涡持续影响华南地区;低层来自孟加拉湾的低空急流与西北太平洋副热带高压南侧偏东风汇合后建立起一条连接华南的水汽通道;在登陆台风影响下,大气视热源和视水汽汇主要来自于垂直运动释放的凝结潜热;湿位涡诊断分析表明强的水平风垂直切变导致低层大气斜压性增强,出现显著的对流不稳定。     

Analysis of an Ensemble of High-Resolution WRF Simulations for the Rapid Intensification of Super Typhoon Rammasun(2014)

Diagnostics are presented from an ensemble of high-resolution forecasts that differed markedly in their predictions of the rapid intensification(RI) of Typhoon Rammasun. We show that the basic difference stems from subtle differences in initializations of(a) 500-850-h Pa environmental winds, and(b) midlevel moisture and ventilation. We then describe how these differences impact on the evolving convective organization, storm structure, and the timing of RI. As expected,ascent, diabatic heating an...     

On the relationship between Arabian Sea warm pool and formation of onset vortex over east-central Arabian Sea

The interannual variability in the formation of mini warm pool (MWP, SST ≥ 30.5°C) and its impact on the formation of onset vortex (OV) over the east-central Arabian Sea (ECAS) are addressed by analyzing the NCEP OIV 2-weekly SST data and NCEP–NCAR reanalysis 850 hPa wind fields from May to June (prior to the onset of monsoon) over the north Indian Ocean for a period of 12 years from 1992 to 2003. Strong interannual variability in the formation and intensification of MWP was observed. Further, the 850 hPa wind fields showed that OV developed into an intense system only during 1994, 1998 and 2001. It formed in the region north of the MWP and on the northern flank of the low-level jet axis, which approached the southern tip of India just prior to the onset of monsoon, similar to the vortex of MONEX-79. The area-averaged zonal kinetic energy (ZKE) over the ECAS (8–15°N, 65–75°E) as well as over the western Arabian Sea (WAS, 5°S–20°N, 50–70°E) showed a minimum value of 5–15 m² s^?2 prior to monsoon onset over Kerala (MOK), whereas a maximum value of 280 m² s^?2 (40–70 m² s^?2) was observed over the ECAS (WAS) during and after MOK. The study further examined the plausible reasons for the occurrence of MWP and OV.     

阿拉伯海热带气旋生成特征分析

利用印度气象局（India Meteorological Department,IMD）、国际气候管理最佳路径档案库（International Best Track Archive for Climate Stewardship,IBTrACS）提供的1982—2020年阿拉伯海热带气旋路径资料,美国国家环境预报中心（National Centers for Environmental Prediction,NCEP）再分析资料,对近39 a阿拉伯海热带气旋源地和路径特征、活跃区域、频数及气旋累积能量（accumulated cyclone energy,ACE）指数的季节特征和年际变化特征进行分析,并结合环境因素,说明其物理成因。结果表明：阿拉伯海热带气旋多发于10°~25°N,65°~75°E海域,5—6月、9—12月发生频数较高且强度较强,1—4月、7—8月发生频数较低且气旋近中心最大风速均小于35 kn;频数的季节变化主要受控于垂直风切变要素;阿拉伯海热带气旋发生频数和ACE近年有上升趋势,年际变化主要受控于海面温度（sea surface temperature,SST）和850 hPa相对湿度要素。     

Characteristics of the Asymmetric Flow of Tropical Cyclone Shanshan (2006) During Its Turning and Intensification Period

In this paper,characteristics of the asymmetric flow of Tropical Cyclone (TC) Shanshan (2006) during its turning and intensification period over the oceanic area east of Taiwan are investigated,based o...     

阿拉伯海夏季季风气旋气流结构和次天气尺度现象的一些特征

本文利用1979年夏季季风实验期间稠密的飞机下投探空仪资料,对一次阿拉伯海季风气旋的垂直气流分布、云层分布、水平螺旋辐合气流和强风环等结构以及它们之间的关系等进行了分析研究。并指出了高空次天气尺度和中尺度的一些现象。垂直气流速度是根据探空仪落速变化算出,把它用在天气系统分析是初次尝试。     

Variation of turbulence in the marine boundary layer over the Arabian Sea during indian southwest monsoon (MONEX 79)

Analysis of high frequency (20 Hz) turbulence data collected from low level flights by the National Center for Atmospheric Research (NCAR) Electra aircraft over the central Arabian Sea on 20 and 24 June, 1979 as part of MONEX 79 indicates the influence of the Somali Jet on boundary-layer turbulence. Different stages of monsoon development were evident on the two observation days from mean boundary-layer profiles. However, turbulence statistics of wind speed components and temperature in the monsoon boundary layer for both days are generally greater than those observed in laboratory experiments or tropical and trade wind boundary layers in which a strong jet was not present. Analysis of high frequency wind, temperature and humidity data was made to obtain fluxes of momentum and heat. Magnitudes of the sensible and latent heat fluxes are three to five times larger than the values observed over the monsoon boundary layer over the Bay of Bengal. The turbulent kinetic energy budget over the Arabian Sea for 24 June indicates the importance of buoyancy, and to a lesser extent shear as the dominant term. Dissipation serves as the primary sink term.     

Kinetic Energy Budgets during the Rapid Intensification of Typhoon Rammasun (2014)

In this study, Typhoon Rammasun(2014) was simulated using the Weather Research and Forecasting model to examine the kinetic energy during rapid intensification(RI). Budget analyses revealed that in the inner area of the typhoon,the conversion from symmetric divergent kinetic energy associated with the collocation of strong cyclonic circulation and inward flow led to an increase in the symmetric rotational kinetic energy in the lower troposphere. The increase in the symmetric rotational kinetic e...     

Statistical and Comparative Analysis of Tropical Cyclone Activity over the Arabian Sea and Bay of Bengal (1977–2018)

A statistical comparative analysis of tropical cyclone activity over the Arabian Sea and Bay of Bengal (BoB) has been conducted using best-track data and wind radii information from 1977 to 2018 issued by the Joint Typhoon Warning Center. Results have shown that the annual variation in the frequency and duration of tropical cyclones has a significant increasing trend over the Arabian Sea and an insignificant decreasing trend over the BoB. The monthly frequency of tropical cyclones in both the Arabian Sea and the BoB shows a notable bimodal character, with peaks occurring in May and October–November, respectively. The maximum frequency of tropical cyclones occurs in the second peak as a result of the higher moisture content at mid-levels in the autumn. However, the largest proportion of strong cyclones (H1–H5 grades) occurs in the first peak as a result of the higher sea surface temperatures in early summer. Tropical cyclones in the Arabian Sea break out later during the first peak and activity ends earlier during the second peak, in contrast with those in the over BoB. This is related to the onset and drawback times of the southwest monsoon in the two basins. Tropical cyclones in the Arabian Sea are mainly generated in the eastern basin, whereas in the BoB the genesis locations have a meridional (zonal) distribution in May–June (October–November) as a result of the seasonal movement of the low-level positive vorticity belt. The Arabian Sea is dominated by western and northwestern tropical cyclones by that track west and NW, accounting for about 74.6%, whereas the tropical cyclones with a NE track account for only 25.4%. The proportions of the three types of tracks are similar in the BoB, with each accounting for about 33% of the tropical cyclones. The mean intensity and size of tropical cyclones over the Arabian Sea are stronger and larger, respectively, than those over the BoB and the size of tropical cyclones over the North Indian Ocean in early summer is larger than that in autumn. The asymmetrical structure of tropical cyclones over North Indian Ocean is affected by the topography and the longest radius of the 34 kt surface wind often lies in the eastern quadrant of the tropical cyclone circulation in both sea areas. FAN Xiao-ting (樊晓婷), LI Ying (李 英), et al.