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1.
Kelvin波和Rossby波是经常出现于海洋中的边界波;南海的复杂岸线、陡变地形和热盐场时空结构的不均匀性具有形成强迫Kelvin波和地形Rossby波的条件。现有研究表明,南海大部分中尺度涡形成于东部一些较大岛屿附近;这些中尺度涡一旦形成后,就在β效应作用下向西移动并最终耗散于西边界,且其波动一般以Rossby波的形式向西传播。因此,南海环流的多涡结构与中尺度波动之间存在着一定的联系。在南海北部,中尺度涡主要由黑潮入侵和风应力旋度所诱生,而在南海南部而以风应力旋度为主要成因。提出了利用线性波动动力学模式来研究南海南部中尺度波动、分析风应力强迫所产生的中尺度波动特征和规律,并据此建立相应的数值模式来揭示该海区环流的动力学和热动力学机制的思路,以便了解该海区流场季节性变化与中尺度波动之间的内在关系。 相似文献
2.
《地球科学进展》2019,(10)
中尺度涡在南海活动频繁,尤其是持续时间长的强中尺度涡对海区内多尺度环流系统的能量输送和物质搬运具有重要调控作用。利用AVISO卫星高度计资料和最外层闭合等值线法,对2011—2018年南海北部的中尺度涡进行识别和追踪,重点讨论中尺度涡在最近几年的时空分布变化。统计结果显示,南海北部平均每年生成8.6个反气旋涡和4.5个气旋涡(持续时间大于28天),其中近1/3为强中尺度涡(持续时间大于45天),表现出较强的涡动能和非线性等动力特征,基本与前人统计的其他年份结果一致。南海北部中尺度涡的生成地点、传播路径以及活动频率分布具有显著的季节变化特征。对比发现,反气旋涡在秋季和冬季主要形成于吕宋海峡北侧,沿等深线向西南移动,最高活动频率超过30%;夏季主要在菲律宾吕宋岛西侧形成,平行于纬线向西移动。而气旋涡在冬季和春季主要形成于吕宋海峡西侧,向西南移动,最高活动频率约为26%。另外,台湾岛西南岸外易生成强中尺度涡涡对,综合黑潮指数进一步分析发现,黑潮入侵南海形成流套是促使该强涡对生成的主要机制。 相似文献
3.
《地球科学进展》2017,(10)
海洋中尺度涡广泛分布于全球海洋且能对大气造成显著影响。在全面陈述大气边界层和局地环流对中尺度涡响应的基础上,论述了与其相应的物理机制,并系统介绍了有关中尺度涡对天气系统影响的最新研究进展。(1)中尺度涡引起的海表温度异常通过改变湍流热通量来引起洋面风速、散度以及云量和降水的异常,并在垂直方向上产生异常的次级环流。并且,大气对中尺度涡的响应有明显的区域和季节差异。(2)在南海、黑潮延伸区和南大洋,中尺度涡可分别通过改变海表面气压或大气边界层稳定度来影响其上的洋面风速。通过分析大气异常中心与中尺度涡的位相关系并配合动力诊断可区分这2种机制。(3)中尺度涡能改变大气中的能量转换从而影响风暴路径和急流位置,并能通过遥相关影响下游地区的天气型。此外,中尺度涡所造成的海洋上层温度变化还将对热带气旋的增强和维持起重要作用。 相似文献
4.
南海南部海洋环流研究的新进展 总被引：16，自引：0，他引：16
综合近期南海南部环流研究的主要成果，描述南海南部的主要流系及其变化。指出研究海区环流主要由季风所驱动。东北季风期，其西部主要由气旋式环流所控制，东部则受较弱的反气旋式环流控制，在二者结合部形成强的逆风海流。西南季风期，海区大部分受反气旋式环流控制，其北侧为一气旋式环流，二者结合部形成强的东向离岸流。还讨论了环流的演变特性和流涡的形成机制。 相似文献
5.
南海海洋环流研究综述 总被引：18，自引：0，他引：18
综述了近二十年来南海海洋环流的主要研究成果，指出太阳辐射、季风和地形是影响南海环流的主要因素；提出了南海环流研究中应特别注意的几个关键问题，即南海环流的平均状态、南海暖流、南海中的局地涡旋、南海暖池、黑潮与南海水的交换、地形对南海环流的作用以及南海水温变化与ENSO的关系等；最后就目前研究中存在的困难提出了相应的对策。 相似文献
6.
在利用南海西沙海域多年声学多普勒流速剖面仪(ADCP)观测流速资料分析近惯性内波运动的生成、传播等演变特征的过程中,发现冬季和夏季的近惯性振荡频率存在整体性的偏移效应。ADCP所处海域位于南海西边界急流区,冬季和夏季的背景环流分别为东北向和西南向,背景环流的方向性差异可能影响近惯性振荡频率的偏移效应。针对背景环流的不同方向,筛选出其对应的近惯性振荡信号,进行合成分析,探讨南海西边界急流如何影响近惯性振荡特征。从背景涡度的角度对这一影响机制做出了解释:夏季时,东北方向背景环流的水平剪切使得局地产生负的背景涡度,近惯性振荡频率往低频方向偏移("红移"现象);冬季时,西南向背景环流的水平剪切导致局地产生正的背景涡度,近惯性振荡频率往高频方向偏移("蓝移"现象)。 相似文献
7.
《地球科学进展》2020,(6)
海洋中广泛存在的中尺度涡旋对动量、能量、热量和物质传输起着至关重要的作用。详细介绍了利用卫星高度计资料识别中尺度涡的闭合等值线、Okubo-Weiss数、绕角和流矢量的方法。结果表明,绝大部分涡旋都呈近刚性旋转的非线性特征,生命周期大于等于16周涡旋的平均寿命、传播距离、振幅和半径分别为32周、550 km、8 cm和90 km。重点介绍了结合卫星高度计和Argo浮标资料合成中尺度涡三维结构的方法。受生成地和移动到当地海洋温盐背景场的共同作用,涡旋呈现不同的三维结构。从演变角度简单介绍了墨西哥湾的回流环和大西洋的地中海涡旋的基本特征。最后,对中尺度涡研究的难点问题,如次中尺度过程、中尺度涡能量耗散和次表层涡旋等进行讨论,并提出今后应从中尺度涡立体化、机动性观测,中尺度涡多学科融合式观测以及多尺度相互作用等方面开展突破性研究。 相似文献
8.
基于NOAA OISST.V2月平均SST资料和FSU月平均风应力资料对南海的SST和风场异常进行了分析,发现：南海对1997/1998年El Nio事件响应最为强烈,并在1997/1998年冬季和次年的夏季SST存在2个异常高峰值,风速存在2个异常减小的极值。为研究南海环流在1997/1998年的异常变化,利用ECOM水动力模型计算了1995—2000年的南海环流场,分析了1998年1月和8月南海水位和环流的异常分布,二者均存在显著的异常：①1月,整个南海海盆为正的水位异常,流场为反气旋异常环流,冬季控制整个南海海盆的气旋式环流减弱;②8月,南海海盆水位为正异常,特别是越南东部海区出现较强的正水位异常,南海南部的高水位中心扩大北移;异常流场表现为南部为气旋式异常环流,北部为反气旋的异常环流,且在越南东部海区形成非常强的反气旋异常环流中心,使得控制南海南部的反气旋环流和北部的气旋环流均减弱。风应力的分析表明,风应力旋度的异常变化是南海环流年际异常变化的主要因素。 相似文献
9.
基于NOAA OISST.V2月平均SST资料和FSU月平均风应力资料对南海的SST和风场异常进行了分析,发现:南海对1997/1998年El Nino事件响应最为强烈,并在1997/1998年冬季和次年的夏季SST存在2个异常高峰值,风速存在2个异常减小的极值.为研究南海环流在1997/1998年的异常变化,利用ECOM水动力模型计算了1995-2000年的南海环流场,分析了1998年1月和8月南海水位和环流的异常分布,二者均存在显著的异常:①1月,整个南海海盆为正的水位异常,流场为反气旋异常环流,冬季控制整个南海海盆的气旋式环流减弱;②8月,南海海盆水位为正异常,特别是越南东部海区出现较强的正水位异常,南海南部的高水位中心扩大北移;异常流场表现为南部为气旋式异常环流,北部为反气旋的异常环流,且在越南东部海区形成非常强的反气旋异常环流中心,使得控制南海南部的反气旋环流和北部的气旋环流均减弱.风应力的分析表明,风应力旋度的异常变化是南海环流年际异常变化的主要因素. 相似文献
10.
《地球科学进展》2016,(5)
中国Argo计划组织实施15年以来,在太平洋和印度洋等海域布放了350多个剖面浮标,建成了我国Argo大洋观测网,并建立了针对Argo剖面浮标的资料接收、处理和分发系统,利用Argo资料开发了多个数据产品,在一定程度上推动了国内海洋数据的共享进程。海量的Argo资料已成为我国海洋和大气科学领域基础研究及业务化应用的主要数据源,特别是在热带气旋(台风)、海洋环流、中尺度涡、湍流、海水热盐储量与输送、大洋水团以及海洋、天气/气候业务化预测预报等方面取得了一批重要的研究和应用成果。随着国际Argo计划由"核心Argo"向"全球Argo"拓展,我国Argo大洋观测网的长期维护和持续发展面临巨大挑战,应紧紧抓住这一难得的机遇,利用国产北斗剖面浮标在南海及邻近我国的西北太平洋和印度洋海域建成Argo区域海洋观测网,为应对全球气候变化及防御自然灾害,更多地承担一个海洋大国的责任和义务。 相似文献
11.
As one of the most important mesoscale ocean features, the mesoscale eddies are omnipresent and have significant impact on the overlying atmosphere. Based on the comprehensive review of the influence of mesoscale eddies on the atmospheric boundary layer and the local circulation, the corresponding physical mechanisms and their impacts on weather systems were presented systematically. ①Eddy-induced SST anomalies may modify the surface wind speed, horizontal divergence, cloud and precipitation through turbulence heat flux anomalies. Meanwhile, additional secondary circulations arise over the eddies. What is more, there are obvious regional and seasonal differences for atmospheric responses. ② Studies in the South China Sea, the Kuroshio Extension region and the Southern Ocean indicate that atmospheric responses to mesoscale eddies can be explained by the changes of sea level pressure or the vertical momentum transport. These two mechanisms can be distinguished by the phase relationship between the atmospheric anomaly center and the eddy core. Diagnosis on the inner dynamical processes may draw better conclusions. ③The energy conversions are affected by mesoscale eddies, which may affect storm tracks and jet streams, and finally result in distant influences on weather patterns. Moreover, sea temperature anomalies from sea surface to the thermocline associated with mesoscale eddies have significant impacts on the intensification and the maintenance of tropical cyclones. 相似文献
12.
Mesoscale eddies, which are widely found in the oceans, play a vital role in momentum, energy, heat and mass transport. The Euler method for identifying mesoscale eddies using satellite altimeter data was presented in detail, including closed SLA contours, OW numbers, Winding-Angle and flow vector methods. The results show that mesoscale eddies are almost nonlinear and solid-body rotation. The long-lived eddies with lifetimes ≥16 weeks have an average lifetime of 32 weeks and an average propagation distance of 550 km. Their mean amplitude and a speed-based radius scale as defined by the automated procedure are 8 cm and 90 km, respectively. The method combining with SLA and Argo profiles to composite the three-dimensional structure were addressed. Due to the different temperature and salt structure in the various oceans of the world, the eddies in different oceans show different three-dimensional structures, which are influenced by both the generation and local temperature and salinity. Two special types of eddies were introduced from the perspective of generation, evolution and dissipation processes, namely the Loop Current Ring in the Gulf of Mexico and Mediterranean eddy in the Atlantic Ocean. Finally, issues including submesoscale processes, dissipation of eddies and subthermocline eddies were discussed, and some future research directions were proposed. 相似文献
13.
Mesoscale eddies are active and energetic in the South China Sea (SCS), and play an important role in regulating the multi-scale circulation and mass transportation in the region, especially for those long-lived strong eddies. Using AVISO altimeter data and outermost closed contour sea level anomaly method, this study identified and tracked mesoscale eddies in the northern SCS during 2011-2018, and focused on the temporal and spatial characteristics of mesoscale eddies in recent years. Similarly to previous results in this region, statistical results show that about 8.6 anticyclonic eddies and 4.5 cyclonic eddies (lifetime > 28 days) were born per year. Among them, about 1/3 of the total number are strong eddies (lifetime > 45 days), showing relatively strong dynamic characteristics, such as strong Eddy Kinetic Energy (EKE) and highly nonlinear feature. Statistics also show significant seasonal variability in mesoscale eddies’ birth places, trajectories and distribution of frequency of occurrence. Specifically, anticyclonic eddies mainly form at the north part of Luzon Strait between autumn and winter, and then move southwestward along isobaths. During this period, the largest value of the frequency of occurrence is over 30%. In summer, most of them form in the west off Luzon Island, and then move westward paralleling to latitude lines. In contrast, cyclonic mainly form in the west off Luzon Strait, and then move westward in winter and spring. During this period, the largest value is about 26%. In addition, observation finds that the strong mesoscale eddy pair could generate off the southwest of Taiwan Island. Analysis of the Kuroshio SCS Index (KSI) implies that loop current caused by Kuroshio intrusion is the most important mechanism for the formation of eddy pair. 相似文献
14.
A comparative modeling approach is used to study the mesoscale dynamics of coastal transition zones in the upwelling systems
of Western Sahara and central California. It is shown that large differences in eddy activity and mixing exist between the
two systems. Since upwelling-favorable winds off Central California and Western Sahara have similar amplitudes, we suggest
that observed and modeled differences in eddy activity are due to differences in configuration parameters. It is argued that
two of these parameters, stratification and topography, eventually affect the energy available for the mesoscales through
baroclinic instability. The large difference in stratification appears to be linked to the salinity structure formed by the
large-scale circulation and is directly related to available potential energy. The shape of the continental shelf affects
the position, structure, and scale of the Ekman divergence, hence upwelling intensity, and frontal formation. The potential
impact of mesoscale eddy mixing and its variability on upwelling ecosystems is discussed. 相似文献
15.
东亚梅雨锋暴雨研究进展 总被引：11，自引：0，他引：11
对梅雨锋的大尺度环流、梅雨锋的次天气尺度和中尺度特征、梅雨锋低空急流和暴雨发展等问题的研究进展作了概述，对低空急流和暴雨发展的各种观点进行了评述，并提出了新的见解和研究结果。 相似文献
16.
中国近海海洋锋和锋面预报研究进展 总被引：1，自引：0，他引：1
海洋锋是水文要素特性不同的2个水团之间的狭窄过渡带,是一种重要的中尺度海洋现象,对渔业、军事和海洋环境保护等许多领域有重要影响,已经成为近年来物理海洋学以及海洋交叉学科中的重要课题之一。中国近海由于众多环流、水团和涡旋在此交汇,海洋锋现象十分显著,近年来,我国学者对中国近海的海洋锋产生机制和变化规律取得了一定的进展。首先从实测水文资料分析、遥感资料分析和数值模拟3个方面分别回顾了黄海、东海、南海北部等中国近海海域海洋锋的研究进展。对于海洋锋的预报研究,我国起步较晚,但目前对近海海洋锋预报的需求十分迫切。回顾总结了国外海洋锋预报的进展,集中介绍了黑潮锋、冰岛—法罗群岛锋、湾流锋和墨西哥湾锋面涡旋的预报方法和现状,最后对如何开展中国近海海洋锋预报提出思考和展望。 相似文献
17.
Ping Zhu 《Natural Hazards》2008,47(3):577-591
Hurricane wind damage constitutes the largest percentage of catastrophic insured losses in the US. Yet the complicated wind
structures and their changes are not fully understood and, thus, have not been considered in current risk catastrophic models.
To obtain realistic landfall hurricane surface winds, a large eddy simulation (LES) framework in a weather forecasting mode
has been developed from a multiple nested Weather Research & Forecasting (WRF) model to explicitly simulate a spectrum of
scales from large-scale background flow, hurricane vortex, mesoscale organizations, down to fine-scale turbulent eddies in
a unified system. The unique WRF-LES enables the high resolution data to be generated in a realistic environment as a hurricane
evolves. In this paper, a simulation of the landfalling Hurricane Katrina is presented to demonstrate various features of
the WRF-LES. It shows that the localized damaging winds are caused by the large eddy circulations generated in the hurricane
boundary layer. With a sufficient computational power, WRF-LES has the potential to be developed into the next generation
operational public wind-field model for hurricane wind damage mitigation. 相似文献
18.
B. N. Goswami 《Journal of Earth System Science》1985,94(3):219-235
A zonally averaged version of the Goddard Laboratory for Atmospheric Sciences (GLAS) climate model is used to study the sensitivity of the northern hemisphere (NH) summer mean meridional circulation to changes in the large scale eddy forcing. A standard solution is obtained by prescribing
the latent heating field and climatological horizontal transports of heat and momentum by the eddies. The radiative heating
and surface fluxes are calculated by model parameterizations. This standard solution is compared with the results of several
sensitivity studies. When the eddy forcing is reduced to 0.5 times or increased to 1.5 times the climatological values, the
strength of the Ferrel cells decrease or increase proportionally. It is also seen that such changes in the eddy forcing can
influence the strength of theNH Hadley cell significantly. Possible impact of such changes in the large scale eddy forcing on the monsoon circulation via
changes in the Hadley circulation is discussed. Sensitivity experiments including only one component of eddy forcing at a
time show that the eddy momentum fluxes seem to be more important in maintaining the Ferrel cells than the eddy heat fluxes.
In the absence of the eddy heat fluxes, the observed eddy momentum fluxes alone produce subtropical westerly jets which are
weaker than those in the standard solution. On the other hand, the observed eddy heat fluxes alone produce subtropical westerly
jets which are stronger than those in the standard solution. 相似文献
19.
The Cretaceous is a special episode in the history of the Earth named for a unique rock type, chalk. Chalk is similar to modern deep-sea calcareous ooze and its deposition in epicontinental seas occurred as these areas became an integral part of the ocean. The shelf-break fronts that today separate inshore from open-ocean waters cannot have existed during the Late Cretaceous probably because the higher sea level brought the base of the wind-mixed Ekman layer above the sea floor on the continental margins.A second peculiarity of the Cretaceous is its warm equable climate. Tropical and polar temperatures were warmer than today. Meridional and ocean-continent temperature gradients were lower. The warmer climate was a reflection of higher atmospheric levels of greenhouse gasses, CO2 and possibly CH4, reinforced by higher water vapor content in response to the warmer temperatures. Most of the additional energy involved in the meridional heat transport system was transported as latent heat of vaporization of H20 by the atmosphere. Poleward heat transport may have been as much as 1 Petawatt (20%) greater than it is today. C3 plants provided for more efficient energy transport into the interior of the continents.Circulation of the Cretaceous ocean may have been very different from that of today. It is impossible for large areas of the modern ocean to become anoxic, but episodes of local anoxia occurred during the earlier Cretaceous and became regional to global during the middle of the Cretaceous. The present ocean structure depends on constant wind systems, which in turn depend on stability of the atmospheric pressure systems forced by polar ice. During most of the Cretaceous the polar regions were ice free. Without polar ice there were seasonal reversals of the high-latitude atmospheric pressure systems, resulting in disruption of the mid- and high latitude wind systems. Without constant mid-latitude westerly winds, there would be no subtropical and polar fronts in the ocean, no well-developed ocean pycnocline, and no tropical subtropical gyres dominating ocean circulation. Instead the ocean circulation would be accomplished through mesoscale eddies which could carry warmth to the polar regions.Greater knowledge and understanding of the Cretaceous is critical for learning how the climate system operates when one or both polar regions are ice free. 相似文献