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1.
60年来西北太平洋上不同强度热带气旋的变化特征   总被引:11,自引:2,他引:9  
利用美国海军联合台风警报中心(JTWC)提供的1945-2005年西北太平洋热带气旋(TC)最佳路径资料统计分析了不同强度TC的时空变化特征.南海北部至巴士海峡以东140°E附近、15°-25°N范围内为不同强度TC出现次数最多的区域,其中巴士海峡东部至140°E附近洋面为强台风和超级台风观测次数最多的区域.TC强度在123°E以西表现为减弱和稳定略占多数,而在123°E以东或20°N以南主要以增强和稳定为主,在20°N以北主要以减弱和稳定为主.热带风暴的平均增强率大于减弱率,而强热带风暴、台风、强台风和超级台风的平均减弱率大于增强率.一般而言,TC的强度越强其加强和减弱的速度都越快.在1年当中,同其他月份相比,6-8月弱TC占的比例相对偏多,而9-11月强TC占的比例相对偏多.不同强度TC的观测次数和个数都存在年、年际或年代际的变化,在长期趋势上,热带风暴的观测次数和形成个数都呈现显著的线性递增趋势,而TC平均强度和其他TC个数均未出现显著的线性递增或递减趋势.在El Ni[AKn~D]o年超级台风个数及其比例显著偏多,而热带风暴、强热带风暴、台风和强台风的总个数显著偏少,TC平均强度显著偏强;而在La Nina年情况相反.  相似文献   

2.
Predicting the intensity of tropical cyclones(TCs)is challenging in operational weather prediction systems,partly due to the difficulty in defining the initial vortex.In an attempt to solve this problem,this study investigated the effect of initial vortex intensity correction on the prediction of the intensity of TCs by the operational numerical prediction system GRAPES_TYM(Global and Regional Assimilation and Prediction System_Typhoon Model)of the National Meteorological Center of the China Meteorological Administration.The statistical results based on experiments using data for major TCs in 2018 show that initial vortex intensity correction can reduce the errors in mean intensity for up to 120-h integration,with a noticeable decrease in the negative bias of intensity and a slight increase in the mean track error.The correction leads to an increase in the correlation coefficient of Vmax(maximum wind speed at 10-m height)for the severe typhoon and super typhoon stages.Analyses of the errors in intensity at different stages of intensity(including tropical storms,severe tropical storms,typhoons,severe typhoons,and super typhoons)show that vortex intensity correction has a remarkable positive influence on the prediction of super typhoons from 0 to 120h.Analyses of the errors in intensity for TCs with different initial intensities indicate that initial vortex correction can significantly improve the prediction of intensity from 24 to 96 h for weak TCs(including tropical storms and severe tropical storms at the initial time)and up to 24 h for strong TCs(including severe typhoons and super typhoons at the initial time).The effect of the initial vortex intensity correction is more important for developing TCs than for weakening TCs.  相似文献   

3.
Yao  Xiuping  Zhao  Dajun  Li  Ying 《Acta Meteorologica Sinica》2020,34(1):150-162

We used tropical cyclone (TC) best track data for 1949–2016, provided by the Shanghai Typhoon Institute, China Meteorological Administration (CMA-STI), and a TC size dataset (1980-2016) derived from geostationary satellite infrared images to analyze the statistical characteristics of autumn TCs over the western North Pacific (WNP). We investigated TC genesis frequency, location, track density, intensity, outer size, and landfalling features, as well as their temporal and spatial evolution characteristics. On average, the number of autumn TCs accounted for 42.1% of the annual total, slightly less than that of summer TCs (42.7%). However, TCs classified as strong typhoons or super typhoons were more frequent in autumn than in summer. In most years of the 68-yr study period, there was an inverse relationship between the number of autumn TCs and that of summer TCs. The genesis of autumn TCs was concentrated at three centers over the WNP: the first is located near (14°N, 115°E) over the northeastern South China Sea and the other two are located in the vast oceanic area east of the Philippines around (14°N, 135°E) and (14°N, 145°E), respectively. In terms of intensity, the eight strongest TCs during the study period all occurred in autumn. It is revealed that autumn TCs were featured with strong typhoons and super typhoons, with the latter accounting for 28.1% of the total number of autumn TCs. Statistically, the average 34-knot radius (R34) of autumn TCs increased with TC intensity. From 1949 to 2016, 164 autumn TCs made landfall in China, with an average annual number of 2.4. Autumn TCs were most likely to make landfall in Guangdong Province, followed by Hainan Province and Taiwan Island.

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4.
Based on high-resolution reanalysis data of the European Centre for Medium-Range Weather Forecasts, several samples of tropical cyclones (TCs), including tropical storms, severe tropical storms, and typhoons, in the South China Sea (SCS), were selected for composite analysis. The structures of these three types of vortices and their differences with ‘bogus’ vortices were investigated. Results showed that TCs in the SCS have characteristics that are distinctly different from vortices formed by the bogussing scheme used at Guangzhou Institute of Tropical and Marine Meteorology, such as no anticyclone in higher layers, strong convergence concentrated at the bottom of the troposphere, and strong divergence happening in higher layers instead of at 400 hPa. These differences provide clues for constructing a more realistic structure for TCs in the SCS. It was also found that the three types of vortices have some structural features in common. The area with high wind speed is fan-shaped in the north around the TC center, the maximum vorticity appears at 925 hPa, the strongest convergence appears at 1000 hPa, and strong divergence is located from 150 to 100 hPa. On the contrary, significant differences between them were revealed. The warm cores in tropical storms, severe tropical storms, and typhoons are located at 600–400 hPa, 400−300 hPa, and 400−250 hPa, respectively. Among the three types of TCs, the bogus vortex of tropical storms has the largest errors in structure and suffers the largest errors in track forecasts. However, typhoons have the largest errors in the forecast of intensity. This may be related to the great impacts of ocean on TC intensity.  相似文献   

5.
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...  相似文献   

6.
The best track data of tropical cyclones (TCs) provided by Regional Specialized Meteorological Center (RSMC) Tokyo for the South China Sea (SCS) from 1977 to 2007 are employed to study the spatiotemporal variations (for a period of 12 hours) and the rapid (slow) intensification (RI/SI) of TCs with different intensity. The main results are as follows. (1) Over this period, the tropical storms (TSs) and severe tropical storms (STSs) mostly intensify or are steady while the typhoons (TYs) mostly weaken. The stronger a TC is initially, the more observation of its intensification and the less its variability will be; the more observation of its weakening is, the larger its variability will be. (2) The TC intensifies the fastest at 0000 UTC while weakening the fastest at 1200 UTC. (3) In the intensifying state, TSs, STSs, and TYs are mainly active in the northeastern, central-eastern, and central SCS respectively. The weakening cases mainly distribute over waters east off Hainan Island and Vietnam and west off the Philippines. Some cases of TSs and STSs weaken over the central SCS. (4) The RI cases form farther south in contrast to the SI cases. The RI cases are observed in regions where there are weaker vertical shear and easterly components at 200 hPa. The RI cases also have stronger mid-and lower-level warm-core structure and smaller radii of 15.4 m/s winds. The SI cases have slightly higher SST.  相似文献   

7.
Recent trends and variability in tropical cyclone (TC) frequency and intensity are examined for TCs that affected China, with particular focus on those TCs that affected China’s key economic zones (e.g., the Yangtze River Delta, the Pearl River Delta, and the Beijing-Tianjin area). The results show that the frequency of TCs affecting China weakly declined during the 1980s and 2000s, followed by a slight increase. The time series of TC frequency shows insignificant variations at periods of 2–6 yr during the past 60 years; these variations are significantly correlated with ENSO activity. The frequency of TCs affecting the Pearl River Delta area is strongly correlated with the ENSO cycle while the frequency of TCs affecting the Yangtze River Delta is not. The TC frequency varies differently for TCs of different intensities. Tropical storms (TSs) affecting China were small in total number, but have clearly increased in frequency. The frequencies of severe tropical storm (STS), typhoon (TY), severe typhoon (STY), and super typhoon (super TY) affecting China declined significantly during the 1970s and 1980s, but the numbers of STY and super TY have increased over the 2000s. The typical intensity of TCs affecting China declined over the 60-yr timeframe, but increased over the most recent 10 years (2000–2010). This increase in the intensity of TCs has particularly impacted the Yangtze River Delta area, which has experienced increased numbers of STYs and super TYs. These tendencies are observed in changes of the maximum intensity of TCs affecting both China in general and the Yangtze River Delta in particular during both the full 60-yr analysis period and the latest 10-yr period; however, these tendencies are not observed in changes of the average intensity of TCs. By contrast, both the extreme intensity and the average intensity of TCs affecting the Pearl River Delta have decreased throughout the analysis period, including the most recent decade.  相似文献   

8.
我国近海热带气旋强度突变的气候特征分析   总被引:10,自引:4,他引:10  
利用2.5×2.5格距的风场及气压资料,计算分析9012号热带气旋登陆后维持65小时不消的各标准时次的角动量收支。得到的结果是:9012号热带气旋登陆后,进入一个相对稳定的鞍型场的中心,低层有西南风急流将大量潮湿空气卷入热带气旋,为其提供充足的潜热能,北侧弱冷空气的侵入,为其提供了斜压能量;而对流层上部气旋4°-8°半径上的地转角动量的涡旋输送及β项产生的气旋角动量的输入,则是气旋中心气压和最大风速维持的直接因素。  相似文献   

9.
利用1945~2011年美国联合台风预警中心(JTWC)西北太平洋热带气旋资料,研究了南海(5°N~25°N,110°E~120°E)与西北太平洋(5°N~25°N,120°E~180°)热带气旋生成位置、生成频数、强度和持续时间的季节变化差异及其成因。从热带气旋路径穿越经度带频数的角度,探讨了ENSO对气旋活动年际变化的影响。结果表明,南海热带气旋活动显著地受季风调控。在南海冬季风作用下,1~4月热带气旋生成于10°N以南且频数较少、强度较弱,这主要是低层气旋式相对涡度和弱东风切变区偏南造成的。相反,受夏季风影响,6~9月是热带气旋生成最多、最频繁的季节,大都生成于南海北部17°N附近。在5月(10月)的季节转换期,生成位置大幅度北进(南撤)且生成频数显著增加(减少),取决于风速垂直切变及中层的相对湿度的急剧转变。11、12月两海域热带气旋生成于10°N以南主要归因于其上空中层大气相对湿度较北部偏大。在西北太平洋,热带气旋生成的季节变化没有南海显著,只在7月有一次明显的变化,7~10月是热带气旋活动的"盛期"。在强度上,西北太平洋大部分区域全年均为弱东风切变,因此热带气旋以台风为主且持续时间长;但南海多为热带风暴。ENSO事件使得不同季节热带气旋生成区域和气旋路径地理位置发生显著变化。在El Nio事件期间,穿越南海所在经度带路径频数为负距平,而西北太平洋经度带为正距平;在La Nia事件期间,情况相反。  相似文献   

10.
Summary One of the greatest challenges in tropical weather forecasting is the rapid intensification (RI) of the tropical cyclone (TC), during which its one-minute maximum sustained wind speed increases at least 30 knots per 24 hours. Here we identify and elucidate the climatic conditions that are critical to the frequency and location of the RI on annual, intraseasonal, and interannual time scales. Whereas RI and formation share common environmental preferences, we found that the percentage of TCs with RI varies annually and from year to year. In August, only 30% of TC actually experiences RI, in contrast to the annual maximum of 47% in November. The proportion of RI in July–September is higher during El Ni?o years (53%) than the corresponding one in the La Ni?a years (37%). Three climate factors may contribute to the increase in the proportion of RI: the southward shift in the monthly or seasonal mean location of the TC formation, the increase in the low-level westerly meridional shear vorticity, and the decrease in northerly vertical shear. When the mean latitude of TC formation increases, the mixed-layer heat content decreases while TC’s inertial stability increases; both are more detrimental to the RI than to TC formation because the RI requires large amount of latent heat energy being extracted efficiently from the ocean mixed layer and requires accelerated low-level radial inflow that carries latent heat reaching the inner core region. We further demonstrate that the RI frequency in the Philippine Sea and South China Sea can be predicted 10 to 30 days in advance based on the convective anomalies in the equatorial western Pacific (5° S–5° N, 130°–150° E) on intraseasonal time scale. The Ni?o 3.4 SSTA in June is a potential predictor for the peak TC season (July–September) RI activity in the southeast quadrant of the western North Pacific (0–20° N, 140–180° E). The RI is an essential characteristic of category 4 and 5 hurricanes and super typhoons because all category 4 and 5 hurricanes in the Atlantic basin and 90% of the super typhoons in the western North Pacific experience at least one RI process in their life cycles. Over the past 40 years, the annual total of RI in the western North Pacific shows pronounced interdecadal variation but no significant trend. This result suggests that the number of supper typhoons has no upward trend in the past 40 years. Our results also suggest that when the mean latitude, where the tropical storms form, shifts southward (either seasonally or from year to year) the proportion of super typhoon or major hurricane will likely increase. This shift is determined by large scale circulation change rather than local SST effects. This idea differs from the current notion that increasing SST can lead to more frequent occurrence of category 4 or 5 hurricanes through local thermodynamics. Corresponding author’s address: Bin Wang, Department of Meteorology, University of Hawaii, 2525 Correa Rd., Honolulu, Hawaii 96822, USA (also visiting professor at the Ocean University of China)  相似文献   

11.
登陆中国不同强度热带气旋的变化特征   总被引:4,自引:3,他引:1  
根据《热带气旋等级》国家标准(2006),将热带气旋(TC)划分为热带低压(TD)、热带风暴(TS)、强热带风暴(STS)、台风(TY)、强台风(STY)、超强台风(SSTY)6个等级,利用中国气象局整编的1949—2006年共58年的《台风年鉴》和《热带气旋年鉴》资料,分析了登陆中国大陆、海南和台湾不同强度TC变化特征。结果表明:(1) 不同强度登陆TC频数存在年际和年代际变化,在长期趋势上,TD、TS登陆频数呈现显著的线性递减趋势,STY登陆频数呈现显著增加趋势。(2) 登陆TD、TS、STS存在6—8年的周期变化,TY具有准16年的周期变化。(3) 登陆TD、TS主要生成于南海东北部海面,登陆TY、STY、SSTY多生成于巴士海峡东南部海面和菲律宾以东洋面。(4) 在年代际变化上,南海生成的登陆TD、TS频数有减少趋势,TY、STY有增多趋势。  相似文献   

12.
The influence of thermal states in the warm pool on tropical cyclones (TCs) in the western North Pacific (WNP) is investigated. There are fewer typhoons during warm years of the warm pool in which tropical storms tend to form in the northwest quadrant and move westward. Inversely, typhoons tend to recurve northeastward to the southeast of Japan and increase in number in the southeast quadrant during cold years. Based on composite analyses, circulation-induced dynamic factors rather than thermal factors are identified as being responsible for TCs activities. During the warm state, the monsoon trough retreats westwards, which leads to anomalous vorticity in low-level and divergence in high-level in the western part of west Pacific. Above-normal TCs activity is found in this area. Furthermore, wind anomalies at 500 hPa determine the main track types. On the contrary, when the warm pool is in cold state, the atmospheric circulation is responsible for the formation of more TCs in the southeast quadrant and recurving track.  相似文献   

13.
西北太平洋暖池热状态对热带气旋活动的影响   总被引:24,自引:9,他引:24  
研究1959-2003年西北太平洋热带气旋与暖池热状况的联系。结果发现暖池次表层海温与生成的台风个数具有显著相关,当暖池处于热状态时,台风偏少,生成热带风暴的位置偏向于靠近大陆的西北侧,且以西行路径为主,因此对我国的影响较为频繁。而暖池处于冷状态时,生成于西北太平洋东南侧的台风较为频繁,西北向移动至日本东南侧易于发生东北的转向。另外,对暖池冷暖状态年的环流合成发现,海表温度不是影响热带气旋年际数量异常的主要因子,而是由大气环流所引发的动力因素起决定作用。当暖池暖状态时,季风槽东端位置偏西北,对应于低层涡度和高层散度为正距平。引发中层垂直上升运动异常。有利于热带气旋在西北侧海域生成。此时500hPa风场以东风距平为主,且西北太平洋南北侧分别为西风和东风垂直切变距平。而暖池处于冷状态时,东亚季风槽东扩,使得西北太平洋东南侧产生有利于气旋生成的环流背景,同时东亚大槽加强,中层西南风易引导热带气旋东北转向,西北太平洋南北侧分别为东风和西风垂直切变距平。  相似文献   

14.
Summary The 1998/99 tropical cyclone (TC) season over northwest Australia was notable for an above average number of TCs (seven compared to five on average) and a number of unusually intense TCs making landfall (three category 5 TCs). The active 1998/99 TC season is attributed here to a combination of a number of broad-scale features over the south east Indian Ocean and the Australian region, with identifiable precursors favoring tropical cyclogenesis. These precursors include: below normal MSLP, abnormally warm ocean temperatures, above average relative humidity in the low- to mid-tropospheric levels and weak wind shears in the genesis region under study, that is, between 10° S to 20° S and 105° E to 135° E. These favorable conditions first appeared as early as August 1998. The appearance of favorable conditions so far ahead of the TC season indicates that they are the likely cause of the enhanced TC activity rather than simply an effect. Although the season as a whole was an active one, strong intra-seasonal variability was evident in that there were two named TCs in December 1998, forming within three days of each other. Only one formed in January 1999 and none in February. By contrast, in March and April 1999, TC activity was enhanced once again, with four named TCs, three of which attained category 5 status. The importance of the above-mentioned precursors in favoring tropical cyclogenesis during the 1998/99 season is discussed in terms of seasonal time scales of the preceding spring and down to synoptic and mesoscale time scales ranging from several days to 48 hours or less. Received October 5, 2001 Revised December 28, 2001  相似文献   

15.
近58年来登陆中国热带气旋气候变化特征   总被引:12,自引:1,他引:11  
杨玉华  应明  陈葆德 《气象学报》2009,67(5):689-696
利用1949-2006年<台风年鉴>和<热带气旋年鉴>资料,主要分析了1949-2006年登陆中国热带气旋的频数、登陆位置、登陆季节延续期和登陆强度等要素及其概率分布的年际和年代际变化特征.结果表明:近58年来,登陆中国热带气旋年频数有减少趋势,但登陆时达台风强度的年频数变化不明显;按登陆地点分区统计发现,登陆华南地区的热带低压及(强)热带风暴年频数以减少为主,而登陆东部地区的热带气旋年频数变化不明显.登陆点历年最北位置(最南位置)有南移(弱的北移)趋势,导致登陆点历年南北最大纬度差逐渐减小,这表明热带气旋登陆区域更为集中,在23°-35°N增多,而在35°N以北和23°N以南以减少为主.登陆中国热带气旋季节延续期缩短了近1个月.热带气旋年平均登陆强度及其概率分布偏度有增加趋势,表明登陆的强台风有增加;登陆中国华南和东部地区的台风强度都有增强趋势,前者比后者趋势更明显.另外,热带气旋年最大登陆强度差长期呈现减小的趋势.  相似文献   

16.
应用NOAA气候预测中心提供的热带大气季节内振荡(MJO)客观业务指数及中国气象局上海台风研究所提供的西北太平洋热带气旋(TC)最佳路径资料集,定量统计榆验了MJO对夏季西北太平洋TC活动的调制作用.结果表明:MJO对TC的生成、强度、路径和登陆活动都有显著的调节作用.当高空辐合中心位于120°E~160°E(MJO位相3~5)时,西北太平洋TC生成偏少,且生成位置偏北;而当高空辐合中心位于10°W~70°E(MJO位相8~10)时,西北太平洋TC生成偏多,且生成位置偏南;随着TC强度加强,能达到显著调节作用的MJO位相逐渐减少,当高空辐合辐散中心位于70°E(MJO位相10)时,对TC强度调制最显著.在路径调节方面,MJO位相1~4和10时,TC活跃于菲律宾以东的西北太平洋上,主要路径为西北偏北行,可能登陆华东、华北;而位相5~8时,TC主要活跃在菲律宾附近及以西到南海,以偏西行路径为主,可能登陆华南.MJO对登陆华南TC也有显著影响.该定量统计检验结果可为TC活动季节内预测提供依据.  相似文献   

17.
The locations(longitudes and latitudes)of the tropical cyclones(TCs)making landfall on the Chinese mainland from 1949 to 2008 are investigated in detail by using ArcGis and FORTRAN routine.The southeast coastline[110 to 122°E)with most landfall TCs was selected as the key region,which was divided into 12 subsections with 1°intervals of longitude.The study period was from July to September in each year.The result showed that the average sustaining time of TCs making landfall on the subsections east of 118°E is longer than those west of 118°E.Before landfall,the averaged TC intensity in the subsections east of118°E is stronger than that west of it.After landfall,however,the difference between the west and east is not significant.The index of destructive potential for the period before/after landfall was defined as TDP1/TDP2.The maximum of TDP1/TDP2 occurred in the subsection of[119,120°E)/[110,111°E).The ENSO impact on the frequency and average location of landfall TC over the whole region at 110 to 122°E is not obvious,but the effect varies with specific subsections.There is little differences of averaged TDP1 in the subsections between different phases of ENSO events,but the averaged TDP2 is larger in the warm events than that in the cold events.The rainstorm days of each station caused by TCs in different subsections were counted respectively.The results suggested that the rainstorm days of the subsections east of 118°E are much more than those west of 118°E.The larger values are primarily distributed at the subsections of[119,120°E)and[110,111°E).  相似文献   

18.
应用中央气象台业务实时资料和中国气象局台风最佳路径资料对2019年发生在西北太平洋和南海的台风活动主要特征以及主要影响我国的台风路径、强度及风雨情况进行了统计分析和论述。2019年西北太平洋和南海共有29个台风生成,较多年平均值偏多2个;秋季台风异常活跃,生成数较常年明显偏多;台风整体强度偏弱,超强台风数与常年持平;有5个台风登陆我国,较多年平均值略偏少;登陆台风平均强度较多年平均值明显偏弱,但台风“利奇马”登陆强度强、风雨影响重。  相似文献   

19.
鉴于热带气旋(TC)对我国沿海地区的影响,研究全球变暖背景下未来登陆我国TC活动的变化,对于我国沿海地区的防灾减灾具有重要意义。基于CMIP5中全球气候模式HadGEM2-ES数据,文中利用区域气候模式RegCM4开展了历史时期和3种情景(RCP2.6、RCP4.5和RCP8.5)下未来东亚区域气候的动力降尺度模拟,检验了模式对历史登陆我国TC活动及其相关大尺度环境场的模拟能力,并预估了3种情景下2030—2039年、2050—2059年和2089—2098年,登陆我国TC的路径、强度和频率的变化特征。结果表明:模式能合理地再现东亚区域历史时期(1986—2005年)大气环流场的空间结构以及登陆我国TC的特征;在3种情景下未来登陆我国TC的平均强度和数量均有不同程度的增加,尤其是台风及以上级别TC的总数明显增加,其中RCP8.5情景最突出,到21世纪末期(2089—2098年)登陆我国TC的平均强度、台风及以上级别TC总数的年平均值较历史时期将分别增加7.56%和1.05个;不同情景下未来登陆我国TC的路径均有不同程度的北移趋势,且全球升温的幅度越大,北移趋势越明显,这可能与未来中国近海显著变暖和垂直风切变减弱有关。未来我国沿海地区尤其是中高纬度很可能将面临日益严峻的TC灾害风险,亟需尽快开展防灾减灾及对策研究。  相似文献   

20.
南海-西北太平洋地区大气准双周振荡对TC生成的调节作用   总被引:3,自引:1,他引:2  
通过对南海-西北太平洋地区大气10~20 d准双周振荡(QBWO)不同位相的划分(A~D),研究了QBWO对南海-西北太平洋海域热带气旋(TC)生成的调节作用。将TC分为强热带风暴及以下级别(TS)和台风及以上级别(TY),并将QBWO分为干湿位相,发现南海海域生成的TS(TY)在干湿位相的比与西北太平洋海域生成的TS(TY)在干湿位相的比相等,这表明QBWO对TS(TY)生成的调节作用在南海和西太平洋地区可能相同。从A位相到C位相,南海和西北太平洋地区TC的生成频数均逐渐增多,D位相时期,TC生成最少,多数TC发生在QBWO的对流活动湿位相,少数TC发生在干位相。南海-西北太平洋海域TC的生成受到QBWO的明显调制。从位相A到位相C,低频对流和低频风场逐渐向西北方向移动,低频对流强度持续加强,低频风场逐渐由异常西风-东风-西风转为异常东风-西风-东风配置,西北太平洋地区季风槽加强,使得TC生成频数逐渐增多。此外,在QBWO活跃位相,非绝热加热增强和纬向风垂直切变减弱也有利于TC的生成。  相似文献   

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