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1.
Based on the simulations of 32 models from the Coupled Model Intercomparison Project Phase 5 (CMIP5), the present study assesses their capacity to simulate the relationship of the summer Asian–Pacific Oscillation (APO) with the vertical zonal wind shear, low-level atmospheric vorticity, mid-level humidity, atmospheric divergence in the lower and upper troposphere, and western Pacific subtropical high (WPSH) that are closely associated with the genesis of tropical cyclones over the western North Pacific. The results indicate that five models can simultaneously reproduce the observed pattern with the positive APO phase accompanied by weak vertical zonal wind shear, strengthened vorticity in the lower troposphere, increased mid-level humidity, intensified low-level convergence and high-level divergence, and a northward-located WPSH over the western North Pacific. These five models are further used to project their potential relationship under the RCP8.5 scenario during 2050–2099. Compared to 1950–1999, the relationship between the APO and the vertical zonal wind shear is projected to weaken by both the multi-model ensemble and the individual models. Its linkage to the low-level vorticity, mid-level humidity, atmospheric divergence in the lower and upper troposphere, and the northward–southward movement of the WPSH would also reduce slightly but still be significant. However, the individual models show relatively large differences in projecting the linkage between the APO and the mid-level humidity and low-level divergence.  相似文献   

2.
Previous studies suggest that spring SST anomalies over the northern tropical Atlantic(NTA) affect the tropical cyclone(TC) activity over the western North Pacific(WNP) in the following summer and fall. The present study reveals that the connection between spring NTA SST and following summer–fall WNP TC genesis frequency is not stationary. The influence of spring NTA SST on following summer–fall WNP TC genesis frequency is weak and insignificant before, but strong and significant after, the late 1980 s. Before the late 1980 s, the NTA SST anomaly-induced SST anomalies in the tropical central Pacific are weak, and the response of atmospheric circulation over the WNP is not strong. As a result, the connection between spring NTA SST and following summer–fall WNP TC genesis frequency is insignificant in the former period. In contrast,after the late 1980 s, NTA SST anomalies induce pronounced tropical central Pacific SST anomalies through an Atlantic–Pacific teleconnection. Tropical central Pacific SST anomalies further induce favorable conditions for WNP TC genesis,including vertical motion, mid-level relative humidity, and vertical zonal wind shear. Hence, the connection between NTA SST and WNP TC genesis frequency is significant in the recent period. Further analysis shows that the interdecadal change in the connection between spring NTA SST and following summer–fall WNP TC genesis frequency may be related to the climatological SST change over the NTA region.  相似文献   

3.
The present study identifies a significant influence of the sea surface temperature gradient(SSTG) between the tropical Indian Ocean(TIO; 15°S-15°N, 40°-90°E) and the western Pacific warm pool(WWP; 0°-15°N, 125°-155°E) in boreal spring on tropical cyclone(TC) landfall frequency in mainland China in boreal summer. During the period 1979-2015, a positive spring SSTG induces a zonal inter-basin circulation anomaly with lower-level convergence, mid-tropospheric ascendance and upper-level divergence over the west-central TIO, and the opposite situation over the WWP, which produces lower-level anomalous easterlies and upper-level anomalous westerlies between the TIO and WWP. This zonal circulation anomaly further warms the west-central TIO by driving warm water westward and cools the WWP by inducing local upwelling, which facilitates the persistence of the anomaly until the summer. Consequently, lower-level negative vorticity, strong vertical wind shear and lower-level anticyclonic anomalies prevail over most of the western North Pacific(WNP), which decreases the TC genesis frequency. Meanwhile, there is an anomalous mid-tropospheric anticyclone over the main WNP TC genesis region,meaning a westerly anomaly dominates over coastal regions of mainland China, which is unfavorable for steering TCs to make landfall in mainland China during summer. This implies that the spring SSTG may act as a potential indicator for TC landfall frequency in mainland China.  相似文献   

4.
Although it is well known that the tropical easterly jet(TEJ)has a significant impact on summer weather and climate over India and Africa,whether the TEJ exerts an important impact on tropical cyclone(TC)activity over the western North Pacific(WNP)remains unknown.In this study,we examined the impact of the TEJ on the interannual variability of TC genesis frequency over the WNP in the TC season(June-September)during 1980-2020.The results show a significant positive correlation between TC genesis frequency over the WNP and the jet intensity in the entrance region of the TEJ over the tropical western Pacific(in brief WP_TEJ),with a correlation coefficient as high as 0.66.The intensified WP_TEJ results in strong ageostrophic northerly winds in the entrance region and thus upper-level divergence to the north of the jet axis over the main TC genesis region in the WNP.This would lead to an increase in upward motion in the troposphere with enhanced low-level convergence,which are the most important factors to the increases in low-level vorticity,mid-level humidity and low-level eddy kinetic energy,and the decreases in sea level pressure and vertical wind shear in the region.All these changes are favorable for TC genesis over the WNP and vice versa.Further analyses indicate that the interannual variability of the WP_TEJ intensity is likely to be linked to the local diabatic heating over the Indian Ocean-western Pacific and the central Pacific El Ni?o-Southern Oscillation.  相似文献   

5.
The influence of the interannual variation of cross-equatorial flow(CEF) on tropical cyclogenesis over the western North Pacific(WNP) is examined in this paper by using the tropical cyclone(TC) best track data from the Joint Typhoon Warning Center and the JRA-25 reanalysis dataset. The results showed that the number of TCs forming to the east of 140°E over the southeastern part of the western North Pacific(WNP) is in highly positive correlation with the variation of the CEF near 125° E and 150° E, i.e., the number of tropical cyclogeneses increases when the cross-equatorial flows are strong. Composite analyses showed that during the years of strong CEF, the variations of OLR, vertical wind shear between 200-850 h Pa, 850 h Pa relative vorticity and 200 h Pa divergence are favorable for tropical cyclogenesis to the east of 140°E over the tropical WNP, and vice versa. Moreover, it is also discussed from the view of barotropic energy conversion that during the years of strong CEF, an eastward-extended monsoon trough leads to the rapid growth of eddy kinetic energy over the eastern part of WNP, which is favorable for tropical cyclogenesis;but during the years of weak CEF, the monsoon trough is located westward in the western part of the WNP, consistent with the growth area of eddy kinetic energy. As a result, there are fewer TC geneses over the eastern part of WNP.Besides, the abrupt strengthening of a close-by CEF 2-4 days before tropical cyclogenesis may be the one of its triggers.  相似文献   

6.
This study investigates characteristics of the convective quasi-biweekly oscillation(QBWO) over the South China Sea(SCS) and western North Pacific(WNP) in spring, and the interannual variation of its intensity. Convective QBWO over the WNP and SCS shows both similarities and differences. Convective QBWO over the WNP originates mainly from southeast of the Philippine Sea and propagates northwestward. In contrast, convective QBWO over the SCS can be traced mainly to east of the Philippines and features a westward propagation. Such a westward or northwestward propagation is probably related to n = 1 equatorial Rossby waves. During the evolution of convective QBWO over the WNP and SCS, the vertical motion and specific humidity exhibit a barotropic structure and the vertical relative vorticity shows a baroclinic structure in the troposphere. The dominant mode of interannual variation of convective QBWO intensity over the SCS–WNP region in spring is homogeneous. Its positive phase indicates enhanced convective QBWO intensity accompanied by local enhanced QBWO intensity of vertical motion throughout the troposphere as well as local enhanced(weakened) QBWO intensity of kinetic energy, vertical relative vorticity,and wind in the lower(upper) troposphere. The positive phase usually results from local increases of the background moisture and anomalous vertical shear of easterlies. The latter contributes to the relationship between the dominant mode and QBWO intensities of kinetic energy, vertical relative vorticity, and wind. Finally, a connection between the dominant mode and the sea surface temperature anomalies in the tropical Pacific Ocean is demonstrated.  相似文献   

7.
2004年和2006年是西北太平洋热带气旋(TC)活动具有明显差别的两年,2004年TC的生成位置主要位于西北太平洋的中东部上空,而2006年的TC主要生成在西北太平洋西部与中国南海.本文利用JTWC(Joint Typhoon Warning Center)热带气旋最佳路径数据、NCEP-DOE AMIP-II再分析资料和NOAA的OLR资料分析并比较了2004年与2006年7~9月西北太平洋上空大尺度环境要素场及天气尺度波动对TC生成的作用.分析结果表明:2004年7~9月与2006年7~9月西北太平洋上空季风槽的平均位置没有明显的区别,但是形态有着显著的差异.2004年季风槽的槽线不明显,在西北太平洋中部呈现一显著的气旋式环流;而2006年季风槽的槽线非常明显,槽线南北两侧呈现平直的水平气流,具有明显的水平切变特征.2004年和2006年对流层低层的相对涡度、高层辐散和垂直风切变具有明显的纬向分布差异,这是这两年TC生成的位置具有明显差异的重要原因之 一.并且,本文还分析对比了2004年以及2006年7~9月西北太平洋上空3~8 d周期的天气尺度波动的活 动,其结果表明:2004年和2006年TC的生成大多数与天气尺度波列的活动有关.2004年的天气尺度波列强度比较强,其活动的位置位于西北太平洋中、东侧上空;而2006年西北太平洋上空的天气尺度波列相对较弱,主要活动于中国南海和西北太平洋西部.纬向基本气流的切变与辐合所引起的瞬变扰动动能倾向的水平分布差异是天气尺度波动活动具有以上差异的重要原因.因此,西北太平洋大尺度环境场与天气尺度波动活动的区别共同造成了2004年7~9月的TC生成位置偏东、而2006年7~9月TC的生成位置偏西.  相似文献   

8.
夏季亚洲-太平洋涛动与中国近海热带气旋活动的关系   总被引：3，自引：2，他引：1  
邹燕  赵平 《气象学报》2009,67(5):708-715
采用联合台风警报中心的台风最伟路径资料和NCEP/NCAR再分析资料,分析了夏季亚洲-太平洋涛动(Asian-Pacif-ic Oscillation,简称APO)与东亚近海-西北太平洋大气环流的关系,并进一步探讨了APO与中国近海热带气旋(tropical cy-clone,简称TC)活动的关系.研究表明:(1)夏季APO强弱与同期西北太平洋及中国东部近海TC活动存在密切关系,即在APO强(弱)年,西北太平洋TC活动偏西(东)和偏北(南),中国东部近海TC明显增多(减少);(2)当APO偏强(弱)时,中国东部近海大气环流有(不)利于TC的维持和发展,表现为低层存在异常气旋性(反气旋性)环流,对流层高低层纬向风垂直切变减小(增大),且对流加强(减弱);(3)APO强弱也影响着TC引导气流的方向:在APO强(弱)年,西北太平洋副热带高压(以下简称副高)偏北和偏东(偏南和偏西),副高南侧偏东气流减弱(加强),有利于TC的向西北行或在偏北(南)纬度西行,进入中国东部近海的TC增多(减少);(4)APO强弱也影响着南海-热带西太平洋TC源地上空的大气环流,在APO强(弱)年,南海-热带西太平洋季风槽偏北、偏西(偏南、偏东),热带西太平洋TC活动偏北和偏西(偏南和偏东),有利于进入中国东部近海TC的增多(减少).  相似文献   

9.
Relationships between large-scale zonal wind anomalies and annual frequency of NW Pacific tropical cyclones and possible mechanisms are investigated with the methods of correlation and composition.It is indicated that when △ U200-△U850 ＞0 in the eastern tropical Pacific and △ U200- △U850 ＜0 in western tropical Pacific, the Walker cell is stronger in the Pacific tropical region and the annual frequency of NW Pacific tropical cyclone are above normal. In the years with zonal wind anomalies, the circulation of high and low troposphere and the vertical motions in the troposphere have significant characteristics. In the time scale of short-range climate prediction, zonal wind anomalies in high and low troposphere are useful as a preliminary signal of the annual frequency prediction of NW Pacific tropical cyclones.  相似文献   

10.
The monsoon trough(MT) is one of the large-scale patterns favorable for tropical cyclone(TC) formation over the western North Pacific(WNP). This study re-examines TC formation by treating the MT as a large-scale background for TC activity during May–October. Over an 11-year(2000–10) period, 8.3 TC formation events on average per year are identified to occur within MTs, accounting for 43.1% of the total TC formation events in the WNP basin. This percentage is much lower than those reported in previous studies. Further analysis indicates that TC formation events in monsoon gyres were included at least in some previous studies. The MT includes a monsoon confluence zone where westerlies meet easterlies and a monsoon shear line where the trade easterlies lie north of the monsoon westerlies. In this study, the large-scale flow pattern associated with TC formation in the MT is composited based on the reference point in the confluence zone where both the zonal and meridional wind components are zero with positive vorticity. While previous studies have found that many TCs form in the confluence zone, the composite analysis indicates that nearly all of the TCs formed in the shear region, since the shear region is associated with stronger low-level relative vorticity than the confluence zone. The prevailing easterly vertical shear of zonal wind and barotropic instability may also be conducive to TC formation in the shear region, through the development of synoptic-scale tropical disturbances in the MT that are necessary for TC formation.  相似文献   

11.
自20世纪70年代末期以来,西北太平洋的热带气旋在全球变暖的背景下主要发生了两种宏观的气候变化：一个是热带气旋生成频数呈现年代际减少,尤其是在东南部海域;另一个则是其生成与活动位置等总体特征有向西北偏移的趋势。本文对这两个方面的研究进展进行了概述。近些年的研究表明,垂直风切变的增强可能是夏秋季热带气旋频数减少的最主要原因,这与太平洋-印度洋海面温度变化导致的大尺度环境变化有密切联系。同样有研究认为北大西洋海面温度的多年代际振荡对近期西北太平洋热带气旋生成频数的减少也非常重要。但西北太平洋西部强热带气旋的频数呈现出增加的趋势,这可能与东亚近海海面温度的显著升高有关,尽管这种变化是否可信仍有争议。近20年来,西北太平洋热带气旋活动普遍出现西北移倾向,包括生成位置和路径位置,这种变化可能受到了ENSO变异及20世纪90年代末期太平洋气候突变的调控。同时,热带环流的极向扩张又导致了热带气旋的有利环境向北扩张,因此西北太平洋热带气旋活动也出现极向迁移的趋势。  相似文献   

12.
关于2006年西太平洋台风活动频次的气候预测试验   总被引：19，自引：2，他引：17  
这是首次利用气候模式对我国2006年夏季西太平洋地区台风活动频次的实时气候预测的报告。根据这个初步的预测试验结果分析,西太平洋地区夏季(6~10月)对流层低层为异常辐散区而高层为异常辐合区,大气顶向外长波辐射为正距平,对流活动异常偏弱;同时,该地区对流层上下层纬向风的切变幅度异常偏大;海洋温度的距平值很小。综合这些气候背景条件,今年西太平洋的台风生成数量将可能比正常年份偏少一些。当然,由于台风生成发展的复杂性,这一预测还有不确定性。  相似文献   

13.
根据热带西太平洋（１３０°－１６０°Ｅ,１０°－２０°Ｎ）上空对流的年际变化,对表面温度、向外长波幅射、８５０ ｈＰａ纬向风进行了合成分析。合成分析结果表明,热带西太平洋上空的弱（强）对流对应着前冬和春季厄尔尼诺（拉尼娜）型的海温异常。与以前的研究结果进行了比较,说明上述海温异常的时空分布也与热带西太平洋和南海季风的爆发早晚相关联。合成分析结果还表明,热带西太平洋上空的弱（强）对流对应着从热带西太平洋向西伸展到盂加拉湾的东风（西风）异常。数值模拟也得到类似的结果。此外,在对流弱（强）的夏季,热带西太平洋上空的对流和南海低层纬向风均表现出弱（强）的季节演变特征。  相似文献   

14.
1998和1999年西北太平洋热带气旋的异常特征及其大尺度条件   总被引：12，自引：5，他引：12  
孙颖  丁一汇 《气象学报》2002,60(5):527-537
应用联合台风警报中心 (JTWC)的资料 ,研究了 1998和 1999年西北太平洋 (WNP)热带气旋 (TC)的活动 ,发现这两年具有较为相似的异常特征 :台风个数明显偏少 ,台风的生成源地显著偏西。对导致这种异常的大尺度条件场的分析表明 ,1998和 1999年的台风季季风槽、垂直风切变、海平面气压等因子的分布都不利于台风在WNP东部海域的生成 ,因此是导致这两年台风偏少和生成源地异常偏西的重要原因。其中 ,季风槽的异常偏西及在盛夏的异常偏北对TC的异常活动产生了主要影响。对低纬大气环流异常的进一步分析表明 ,WNP地区的环流异常是导致季风槽和垂直风切变场异常的主要原因 ,而 1999年异常环流的出现可能是由于低纬大气对印尼附近异常热源强迫的响应所致。由于该热源的存在 ,在其东侧 (WNP地区 )激发出东传的Kelvin波 ,而相应的异常风场则表现为低层盛行异常东风 ,而高层盛行异常西风 ,因此造成了WNP东部和西部海域垂直切变场的近乎相反的变化。同时 ,由于低层异常强的东风不利于季风西风的向东延伸 ,从而使季风槽明显偏西 ,未到达菲律宾以东的热带气旋频发区的位置。  相似文献   

15.
The Tropical Cyclone Genesis Potential Index (GPI) was employed to investigate possible impacts of global warming on tropical cyclone genesis over the western North Pacific (WNP). The outputs of 20th century climate simulation by eighteen GCMs were used to evaluate the models’ ability to reproduce tropical cyclone genesis via the GPI. The GCMs were found in general to reasonably reproduce the observed spatial distribution of genesis. Some of the models also showed ability in capturing observed temporal vari...  相似文献   

16.
2010年西北太平洋与南海热带气旋活动异常的成因分析   总被引：1，自引：0，他引：1  
利用中国气象局热带气旋（TC）资料、NCEP/NCAR 再分析资料和美国 NOAA 向外长波辐射（OLR）等资料,分析了2010年西北太平洋（WNP）及南海（SCS）热带气旋活动异常的可能成因,讨论了同期大气环流配置和海温外强迫对TC生成和登陆的动力和热力条件的影响。结果表明,2010年生成TC频数明显偏少,生成源地显著偏西,而登陆TC频数与常年持平。导致7～10月TC频数明显偏少的大尺度环境场特征为：副热带高压较常年异常偏强、西伸脊点偏西,季风槽位置异常偏西,弱垂直风切变带位置也较常年偏西且范围偏小,南亚高压异常偏强,贝加尔湖附近对流层低高层均为反气旋距平环流,这些关键环流因子的特征和配置都不利于 TC 在WNP的东部生成。影响TC活动的外强迫场特征为：2010年热带太平洋经历了El Ni?o事件于春末夏初消亡、La Ni?a事件于7月形成的转换;7～10月,WNP海表温度维持正距平,140°E以东为负距平且对流活动受到抑制;暖池次表层海温异常偏暖,对应上空850 hPa为东风距平,有利于季风槽偏西和TC在WNP的西北侧海域生成。WNP海表温度和暖池次表层海温的特征是2010年TC生成频数偏少、生成源地异常偏西的重要外强迫信号。有利于7～10月热带气旋西行和登陆的500 hPa风场特征为：北太平洋为反气旋环流距平,其南侧为东风异常,该东风异常南缘可到25°N,并向西扩展至中国大陆地区;南海和西北太平洋地区15°N以南的低纬也为东风异常;在这样的风场分布型下,TC容易受偏东气流引导西行并登陆我国沿海地区。这是2010年生成TC偏少但登陆TC并不少的重要环流条件。  相似文献   

17.
Summary This paper reviews the interannual and interdecadal variations in tropical cyclone (TC) activity over the western North Pacific (WNP) and the possible physical mechanisms responsible for such variations. Interannual variations can largely be explained by changes in the planetary-scale flow patterns. Sea-surface temperatures (SSTs) in the WNP, however, do not contribute to such variations. Rather, SSTs in the central and eastern equatorial Pacific are significantly correlated with TC activity over the WNP. Causality can be established: changes in the SST in the equatorial Pacific are related to the El Niño/Southern Oscillation (ENSO) phenomenon, and modifications of the planetary-scale flow associated with ENSO alter the conditions over the WNP and hence TC activity there. Variations in annual TC activity are also associated with different phases of the stratospheric quasi-biennial oscillations due to its modification of the vertical wind shear of the environment in which TCs form. Interdecadal variations in TC activity are apparently related to the location, strength and extent of the North Pacific subtropical high. However, the mechanisms responsible for modifying these characteristics of the subtropical high have yet to be identified.  相似文献   

18.
Future changes in tropical cyclone(TC)activity over the western North Pacific(WNP)under the representative concentration pathway RCP4.5 are investigated based on a set of 21 st century climate change simulations over East Asia with the regional climate model RegCM4 driven by five global models.The RegCM4 reproduces the major features of the observed TC activity over the region in the present-day period of 1986-2005,although with the underestimation of the number of TC genesis and intensity.A low number of TCs making landfall over China is also simulated.By the end of the 21st century(2079-98),the annual mean frequency of TC genesis and occurrence is projected to increase over the WNP by16%and 10%,respectively.The increase in frequency of TC occurrence is in good agreement among the simulations,with the largest increase over the ocean surrounding Taiwan Island and to the south of Japan.The TCs tend to be stronger in the future compared to the present-day period of 1986-2005,with a large increase in the frequency of strong TCs.In addition,more TCs landings are projected over most of the China coast,with an increase of~18%over the whole Chinese territory.  相似文献   

19.
利用1981—2020年中国热带气旋最佳路径数据集、中国大气再分析资料(CMA-RA)、欧洲中期天气预报中心ERA5及美国NCEP/NCAR再分析资料(NCEP-Ⅰ),对比不同资料在表征影响南海热带气旋活动环流背景的能力,探讨CMA-RA的适用性。结果表明:不同资料基本刻画出与热带气旋活动密切相关的环流特征,包括南方涛动、菲律宾至南海低层纬向风、热带低层纬向风反向分布型、菲律宾至南海中东部低层涡度、热带西太平洋垂直风切变及南海至菲律宾以东海域中层湿度。它们对南方涛动、关键区纬向风和中层湿度的刻画较相似,CMA-RA和ERA5对南方涛动、低层纬向风及其与热带气旋关系的描述一致性高,较NCEP-Ⅰ密切,但低层经向风、关键物理量差异较大。对极端年环流具有相似的表现能力,但异常程度存在差异,海平面气压、低层纬向风高度一致,以CMA-RA与ERA5最接近;中层湿度CMA-RA与ERA5接近,较NCEP-Ⅰ偏小;关键物理量差异较大。CMA-RA对南海热带气旋环流的刻画具有与ERA5和NCEP-Ⅰ相当的性能,并与ERA5一致性较高,可为相关工作提供可替换的再分析资料集。  相似文献   

20.
Using tropical cyclone （TC） observations over a 58-yr period （1949-2006） from the China Meteorological Administration, the 40-year ECMWF Reanalysis （ERA-40）, NCEP-NCAR reanalysis, and the Hadley Centre sea ice and sea surface temperature （HadISST） datasets, the authors have examined the behaviors of tropical cyclones （TCs） in the western north Pacific （WNP） in boreal winter （November-December-January-February）. The results demonstrate that the occurrences of wintertime TCs, including super typhoons, have decreased over the 58 years. More TCs are found to move westward than northeastward, and the annual total number of parabolic-track-type TCs is found to be decreasing. It is shown that negative sea surface temperature anomalies （SSTAs） related to La Nifia events in the equatorial central Pacific facilitate more TC genesis in the WNP region. Large-scale anomalous cyclonic circulations in the tropical WNP in the lower troposphere are observed to be favorable for cyclogenesis in this area. On the contrary, the positive SSTAs and anomalous anticyclonic circulations that related to E1 Nifio events responsible for fewer TC genesis. Under the background of global warming, the western Pacific subtropical high tends to intensify and to expand more westward in the WNP, and the SSTAs display an increasing trend in the equatorial eastern-central Pacific. These climate trends of both atmospheric circulation and SSTAs affect wintertime TCs, inducing fewer TC occurrences and causing more TCs to move westward.  相似文献   

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