近50年登陆我国热带气旋时空特征及对农业影响研究综述

文章回顾并总结了近50年登陆我国热带气旋时空特征,并基于农业气象观测资料和部门数据信息初步探讨了登陆我国热带气旋对农业影响的时空特征。近50年登陆我国热带气旋登陆区域呈现出更为集中的趋势,年平均登陆强度、强台风数量均呈增加趋势;登陆频次华南呈减少趋势,华东则变化不明显;北上热带气旋略有上升趋势。我国受热带气旋影响地区的热带气旋降水大部呈波动下降的趋势;热带气旋平均风速最大值在全国呈现降低趋势。热带气旋暴雨和大风对农业的影响主要造成农田洪涝灾害、“雨洗禾花”、水土流失和耕地质量下降、作物倒伏和机械损伤等,其中农田洪涝灾害最重。我国农业生产受热带气旋影响存在较明显时空特征。秋季主要受影响区域为华南、江南东南部,大宗作物中晚稻受影响最大。盛夏受影响区域更为广泛,华南南部和东部、江南东部、江淮东部等地沿海受影响最重,南方受影响较大的大宗作物是早稻,其次为晚稻和一季稻等;盛夏季节热带气旋在带来暴雨洪涝和大风灾害的同时,也减少了南方盛夏季节性高温和干旱的发生;盛夏北上热带气旋因其带来的充沛降水对农业影响总体利大于弊。从农业生产防灾减灾的长效机制角度,在大数据基础上深入研究热带气旋对我国农业影响时空分布规律,积极发展避灾农业相关技术,是未来工作的重要方面。     

Study on climatic characteristics of China-influencing tropical cyclones

Analysis of the climatic characteristics of the tropical cyclones that affect China yields several interesting features. The frequency of these tropical cyclones tended to decrease from 1951 to 2005, with the lowest frequency in the past ten years. The decrease in the frequency of super typhoons is particularly significant. The main season of tropical cyclone activities is from May to November, with an active period from July to September. There are three obvious sources of these tropical cyclones and they vary with seasons and decades. Their movement has also changed with seasons. On average, these tropical cyclones affect China for 5.6 months annually and the period of influence decreases in the past decades. An analysis of daily data indicates that the days of typhoon influence are shorter in winter and spring and longer in summer. The frequency of tropical cyclones is the largest over southeastern China, decreasing northwestward. Taiwan is the region that is affected by tropical cyclones most frequently. The average annual precipitation associated with tropical cyclones has also decreased gradually northwestward from southeastern China.     

The formation of tropical cyclones

Summary This paper attempts a synthesis of new observations and new concepts on how tropical cyclone formation occurs. Despite many worthy observational and numerical modeling studies in recent decades, our understanding of the detailed physical processes associated with the early stages of tropical cyclone formation is still inadequate; operational forecast skill is not very high. Although theoretical ideas cover a wide range of possibilities, results of new observations are helping us to narrow our search into more specific and relevant topic areas.With 33 FiguresPrologueThis paper is dedicated to Professor Herbert Riehl under whom I studied tropical meteorology at the University of Chicago from 1957–1961 and was later associated with at Colorado State University (CSU). Professor Riehl arranged my first aircraft flights into hurricanes in the late 1950s and gave great encouragment to me to explore the secrets of what causes a tropical disturbance to be transformed into a tropical storm.Herbert would persist in asking me nearly every week or so what causes a hurricane to form? I and my graduate students and research colleagues at CSU have been working to uncover the secrets of tropical cyclone formation ever since. The following article gives my current best estimate of the primary physical processes involved with this topic.     

The motion of binary tropical cyclones

Summary When two tropical cyclones are present simultaneously in the same region they show as a rule a counterclockwise rotation around each other. A theoretical explanation of this motion is given. The theory permits the computation of the rate of rotation. A discussion of nine examples with sufficiently reliable and complete observational data gives a satisfactory agreement between theoretical and observed rates of rotation.

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Zusammenfassung Es ist häufig beobachtet worden, daß zwei tropische Zyklonen sich entgegen dem Uhrzeigersinne umeinander bewegen. Eine theoretische Erklärung dieser Bewegung kann gegeben werden auf Grund der Annahme, daß sich jedes Zyklonenzentrum unter dem Einfluß des Windfeldes der anderen Zyklone bewegt; auf Grund dieser Theorie läßt sich die Rotationsgeschwindigkeit des Zyklonenpaares berechnen. An Hand von neun Fällen mit genügend zuverlässigem und vollständigem Beobachtungsmaterial wird gezeigt, daß gute Übereinstimmung zwischen Theorie und Beobachtung besteht.

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Résumé On a souvent observé que deux cyclones tropicaux se meuvent l'un par rapport à l'autre dans le sens inverse des aiguilles d'une montre. On peut expliquer le fait en admettant que chaque centre cyclonique se déplace sous l'influence du champ de vent de l'autre. Grâce à cette hypothèse on peut calculer la vitesse de rotation de la paire de cyclones. Neuf exemples richement documentés montrent un bon accord entre la théorie et l'observation.

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With 3 Figures.     

Numerical simulation of tropical cyclones by an axisymmetric nonhydrostatic model

Summary As an approach to study the mesoscale processes within a typhoon, an axisymmetric nonhydrostatic numerical model is developed without the use of convective parameterization. Many simulated characteristics are consistent with radar and aircraft observations, such as the maximum of vertical and tangential wind, the inflow concentrated near the surface, the outward slope of the eyewall updraft, etc. The model duplicates not only the outward propagation of mesoscale convective systems, but also the inward movement of convective rings, the rate of which coincides with the observation. Besides, the model gives good simulations of the life cycle of convective rings, and indicates that the convective rings far from the eyewall play important roles in the fluctuation of typhoon intensity. Numerical results also exhibit the existence of coupling between outer and inner core structure.Analyses of the simulations show that convective momentum transport generates local maximum absolute angular momentum in the middle and upper troposphere. The momentum anomaly results in symmetric instability, which provides the environment to form convective rings. While the momentum anomaly moves outward with the outflow in the middle and upper troposphere, it initiates a series of convective rings with aid of other direct factors, which explains the outward propagation of convective systems.The simulations exhibit the life cycle of a typical convective ring in terms of three stages, or the developing, mature and dissipating stage. Analysis shows that the symmetric instability and the convective instability promote each other, and their cooperation makes the life of convective rings longer.With 8 Figures     

登陆青岛的热带气旋及其降水特征分析

利用中国台风年鉴资料、地面及探空观测资料、NCEP／NCAR再分析数据以及NERA-GOOS海温数据,首先分析了1949—2019年在青岛登陆的四个热带气旋特征,然后对1909号台风“利奇马”对山东半岛造成的降水强度差异进行对比研究。分析表明:1)1949年以来有4个台风于8月以登陆北上和登陆转向路径在青岛登陆,其在中高纬均是纬向环流占优的大尺度环流形势,副热带高压主体维持在我国东部沿海上空,中心强度较常年偏强,西伸脊线在30°～36°N之间摆动,青岛沿海海域表现为27 ℃以上的暖洋面特征。2)来自中高纬的冷空气和热带系统在青岛相互作用的差异,副热带高压强度和中心位置的不同是影响登陆台风降水差异的主要原因。3)1909号台风“利奇马”对潍坊降水的影响主要发生在台风与西风槽相互作用过程中,对青岛则表现为台风低压环流前部东南气流的影响。4)台风过程中潍坊和青岛均具有较好的水汽条件和对流不稳定层结,但动力抬升条件差异明显:潍坊位于东北风和东南风辐合区以及水汽通量辐合大值区内,具有较强的水平风垂直切变和上升运动;青岛没有冷空气侵入,但低空和超低空强盛的东南风急流为青岛暴雨提供了充沛的水汽供应和大气层结不稳定条件。     

登陆我国热带气旋频数和强度变化的气候特征

本文利用数理统计方法,对登陆我国的热带气旋频数进行分析。发现热带气旋登陆前24、12、6小时近中心最大风速V_1、V_2、V_3分别与登陆后24小时平均最大风速和它们的差值成线性关系。求得了登陆我国台湾、海南、广东、福建四省的V_1、V_2、V_3与/V_1、/V_2、/V_3的回归方程。另外,对登陆我国热带气旋的频数及强度变化进行了气候分析,指出了一些气候特征。     

伊春气温因子的时空变化特征

选取伊春市1971-2010年的气温观测资料,进行气温因子的时空变化特征分析.结果表明,伊春近40a的年平均气温呈明显的上升趋势,平均上升0.39 ℃/10 a.1971-1987年处于偏冷期,1988-2010年为增暖期,气温增幅明显.伊春近40a的高温天气日数呈上升趋势,低温天气日数呈显著下降趋势.年平均气温逐年代上升,幅度较大,71-80年代气温非常寒冷,近代变暖显著.     

Rainfall generator with spatial and temporal characteristics

The aim of this paper is to present a rainfall generator which takes both spatial and temporal characteristics into account. The statistical model behind the generator is based on long-time experience with statistical analyses of empirical rainfall data and represents, therefore, a genuine theoretical point for simulating series of precipitation values. The sites of the recording gauges and the actual time (day, month, year etc.) enter a statistical model as systematic components for the prediction of expected rainfall in a two-way analysis of variance design. Beyond these systematic components, spatial correlations among the observations are still present in nature, a feature which is modelled also by the rainfall generator.     

Variation characteristics of tropical cyclones making landfall in China at different intensities

According to the national standard(2006)on tropical cyclone(TC)intensity,TCs are categorized into six intensity types,namely,tropical depression(TD),tropical storm(TS),severe tropical storm(STS), typhoon(TY),severe typhoon(STY),and super severe typhoon(SSTY).Fifty-eight years(1949–2006)of the datasets from the Yearbook of Typhoons and Yearbook of Tropical Cyclones were used to study the variation characteristics of TCs making landfalls in mainland China,Hainan and Taiwan islands.The main results are as foll...     

Studying an interaction between tropical cyclones and jet streams using the numerical simulation data

Discussed are the results of studying an evolution of tropical cyclones (TCs) in the Pacific Ocean using the data of computation of ETA and WRF NMM mesoscale numerical atmospheric models. Computed are the trajectories of TCs and the fields of meteorological variables in the typhoons, of the wind speed and kinetic energy in the subtropical jet stream during the development of Parma, Melor, and Lupit typhoons. Carried out are the analysis and comparison of computed fields of pressure, wind, kinetic energy, and trajectories of TCs obtained using these models and their comparison with the actual fields. It is demonstrated that both models computed rather well the complex trajectories and the fields of wind and kinetic energy varying in the course of the interaction. Proposed is an explanation of processes taking place during the interaction between the vortices and the subtropical jet stream and the polar front.     

我国热带气旋研究十年进展

利用中国气象局上海台风研究所（CMA-STI）1949-2015年热带气旋（TC）最佳路径数据集和NCEP/NCAR再分析资料,对西北太平洋（含南海海域）1949-2015年TC快速增强（RI）集中区位置变化和影响因素等进行统计分析。结果表明：（1）RI的发生频数及伴有RI发生的TC频数均呈减少趋势,RI持续时间占TC生命史的比例及伴有RI发生的TC占TC总频数的比例呈震荡减小趋势。（2）RI集中区北界南移、南界北移,总体收缩南移,东界西移、西界东移,总体收缩西移。（3）西北太平洋环境风垂直切变（VWS）的弱切变区向西向南的气候漂移和海表面温度正距平区域的向南扩展是导致发生RI的TC最北纬度显著向南漂移的可能原因,发生RI的TC最南纬度向北的漂移则可能与高海表面温度（SST）向北扩展密切相关。（4）RI集中区的200 hPa高空辐散变强、850 hPa水汽输送加强等有利环境场条件的叠加,也对RI集中区的气候漂移有重要影响。

     

Eta model forecasts of tropical cyclones from Australian Monsoon Experiment: The model sensitivity

Summary The Australian Monsoon Experiment (AMEX) (10 January through 15 February 1987) has resulted in the first ever quality mesoscale data set in the Australian tropics. This provides the first observational confirmation of previous hypotheses, modelling experiments and refinement of the parametrization of convective processes. During the AMEX a large area of convective activity off northwestern Australia accompanied four tropical cyclones onset:Connie, Irma, Damien andJason. As already reported by the author, the Eta Model of the University of Belgrade and the National Meteorological Centre, Washington (UB/NMC), successfully predicted the development, structure, associated precipitation and tracks of these cyclones.Using again the AMEX tropical cyclone cases, in the present study the sensitivity of the Eta Model is examined with respect to the initial and boundary conditions, the vertical coordinate and orography, the location of the initial vortex, the surface fluxes of heat and moisture, the sea surface temperature and the Betts-Miller convection parametrization scheme.Also, some available forecasts of the AMEX tropical cyclones were intercompared. These included the forecasts obtained by the Eta Model, the T106 global (then) operational European Centre for Medium-range Weather Forecasts (ECMWF) model, the ECMWF T106 limited area model and the Florida State University (FSU) limited area model. A review of the intercomparison results suggests that the Eta Model is highly competitive with the other sophisticated models, both in terms of quality and the computational effort required.With 9 Figures     

On the formation and development of tropical cyclones

A method of diagnostic calculation of the maximal wind speed in the tropical cyclone, its radius, and central pressure is proposed taking into account large-scale air motions in a low-gradient baric field between subtropical anticyclones. The results of such calculations are considered. A conclusion is made about sufficient accuracy of calculations of the parameters within the tropical zone using only dynamic factors.     

登陆TC低压再度引发的特大暴雨诊断分析

利用客观分离方法及其改进方案提取得到热带气旋(TC)降水量,统计1965—2013年TC衰减成为热带低压后24 h内发生暴雨的个例,研究其气候变化特征,并进行天气学分型。结果表明：广西东部、广东、福建南部是TC衰减后24 h内产生区域性暴雨(简称WTCR₂₄)量的主要分布区;49 a来WTCR₂₄频次具有缓慢减少的趋势,且WTCR₂₄频次与TC频次具有较好的相关性;北部高压坝、鞍型场、并入高空槽3类环流型中,TC是否越过副热带高压脊线、副热带高压是否减弱是降水预报的转折点;较弱的TC何时并入较强的TC环流,是双台风型WTCR₂₄发生的关键。

     

热带气旋大风风圈半径非对称性特征及成因简析

为进一步完善热带气旋大风风圈的分析和预报业务,利用中央气象台（NMC）发布的热带气旋报文资料、ERA5再分析资料,研究了2015年6月30日至2020年12月31日热带气旋最大强度时的7、10和12级风圈的非对称性特征及成因。统计结果表明: 热带气旋的7级风圈半径非对称性最大,10级次之,12级最小;非对称分布热带气旋的7、10和12级风圈最大半径大多分布在东北、东南和西北象限;同一热带气旋的7级和10级风圈最大半径大多分布在相同的象限。将7级风圈单一象限分布的热带气旋与多象限分布的热带气旋各按象限分布分成4类,分析4类7级风圈单一象限分布的热带气旋生成季节、地面10 m风特征及风圈非对称分布的成因发现:各类热带气旋具有明显的季节特征;地面10 m风场呈不对称分布;风圈非对称分布与西太平洋副热带高压、西南气流及地面冷高压等天气系统与热带气旋的相互作用造成的各象限位势高度梯度非对称分布密切相关。      

2015年西北太平洋和南海台风活动特征及主要预报技术难点

利用常规气象观测资料、1949—2015年中国气象局台风最佳路径资料、2015年中日美台风实时定位资料、1°×1°的NOAA/OISST月平均海温资料和NCEP/FNL再分析资料以及05°×05°的NCEP RTG实时海温等资料,对2015年西北太平洋和南海台风活动的主要特征、厄尔尼诺对该年台风整体活动的影响、1508号台风“鲸鱼”实时定位、1522号台风“彩虹”近海急剧加强预报、1510号台风“莲花”和1521号台风“杜鹃”长时效路径预报以及地面观测系统存在的薄弱环节等主要业务技术难点和问题进行了初步分析。结果表明： 1）2015年台风活动活跃期不明显,呈现生成总数与多年平均持平、南海台风偏少、生成源地偏东、强度强、超强台风异常偏多、登陆个数及频次偏少等特征。2）2015年台风主要活动特征与极强厄尔尼诺事件关系密切,但厄尔尼诺对台风的影响不是单一的,其影响物理机制尚待深入研究。3）台风“鲸鱼”实时业务定位的精度直接影响其登陆预报的精度,综合应用多源观测资料、规范台风定位业务流程,有利于台风定位和路径预报精度的提高。4）台风快速增强和路径长时效预报仍是台风业务的主要技术瓶颈,高分辨率台风-海-气-浪耦合模式、集合预报及相关动力统计模式和天气物理概念模型的研发改进将是未来的主要解决技术途径。5）中国地面观测系统尚不具备对极端台风的监测能力,在沿海受台风影响的重点区域（包括海岛）布设先进的重型机械式强风仪,将有助于提高对极端台风事件的监测能力。     

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。     

The effect of surface friction on the development of tropical cyclones

When tropical cyclones (hereafter referred as TCs) are over the ocean, surface friction plays a dual role in the development of TCs. From the viewpoint of water vapor supply, frictional convergence and Ekman pumping provide a source of moisture for organized cumulus convection and is propitious to the spin-up of TCs. On the other hand, surface friction leads to a dissipation of kinetic energy that impedes the intensification of TCs. Which role is dominant in the developing stage of TCs is a controversial issue. In the present work, the influence of surface friction on the growth of TCs is re-examined in detail by conducting two sets of numerical experiments initialized with different cyclonic disturbances. Results indicate that, because of the inherent complexities of TCs, the impact of surface friction on the evolution of TCs can not be simply boiled down to being positive or negative. In the case that a TC starts from a low-level vortex with a warm core, surface friction and the resultant vertical motion makes an important contribution to the convection in the early developing stage of the TC by accelerating the build-up of convective available potential energy (CAPE) and ensuring moisture supply and the lifting of air parcels. This effect is so prominent that it dominates the friction-induced dissipation and makes surface friction a facilitative factor in the spin-up of the TC. However, for a TC formed from a mesoscale convective vortex (MCV) spawned in a long-lasting mesoscale convective system (MCS), the initial fields, and especially the low-level humidity and cold core, enable the prerequisites of convection (i.e., conditional instability, moisture, and lifting), to be easily achieved even without the help of boundary-layer pumping induced by surface friction. Accordingly, the reliance of the development of TCs on surface friction is not as heavy as that derived from a low-level vortex. The positive effect of surface friction on the development of TCs realized through facilitating favorable conditions for convection is nearly cancelled out by the friction-induced dissipation. However, as SST is enhanced in the latter case, the situation may be changed, and different development speeds may emerge between model TCs with and without surface friction considered. In short, owing to the fact that TC development is a complicated process affected by many factors such as initial perturbations, SST, etc., the importance of surface friction to the intensification of TCs may vary enormously from case to case.     

吐鲁番地区暖季降水时空分布特征

以吐鲁番5个国家气象站近55 a(1960—2014年)与26个区域气象站近3 a(2013—2015年)逐小时降水资料为基础,利用Pearson相关分析、气候倾向率、Mann-Kendall突变分析、Morlet小波分析等方法,分析了吐鲁番地区暖季降水时空分布特征,并就地形对吐鲁番降水的影响进行了量化研究。结果表明:在新疆趋暖趋湿的气候背景下,吐鲁番盆地平原区和山区存在截然不同的降水时空变化特征,吐鲁番地区降水高度集中在暖季,且暖季山区降水集中度和稳定性更好;暖季盆地内存在频率55%的夜雨区和昼雨区,盆地西南坡地和腹地平原区为夜雨区,盆地北部天山山区降水则集中在午后,海拔高度大约每增加(减少)300 m,降水集中时段提前(延后)1 h。研究还表明,吐鲁番降水与地形关系密切,海拔高度是影响吐鲁番降水的决定性因素,其暖季降水量、降水时数均与海拔高度呈显著正相关,降水量增加的主要原因是降水时数随海拔高度的递增;降水量随海拔高度的变化呈二次曲线型,其最大降水高度为1900 m;在最大降水高度以下,降水量由盆地腹地的平原区向山区递增,降水垂直变率平均为6.2 mm/100 m,其中1500~1900 m高度是降水量与降水垂直变率最大的区域,降水垂直变率达20 mm/100 m。