中尺度涡旋影响吕宋海峡黑潮变异的动力机制

使用1.5层约化重力准地转模式,研究了西边界流在西边界缺口处当处于迟滞过程的临界状态时,其路径转变受中尺度涡旋影响的动力机制,初步探讨了中尺度涡旋影响西边界流在缺口处路径变化的几种形式.结果表明,气旋和反气旋中尺度涡旋都可能使西边界流产生由入侵流态到跨隙流态的转变,而只有反气旋式中尺度涡才有可能诱发西边界流由跨隙流态向入侵流态的转变.当西边界流远离其临界状态时,其路径不容易受中尺度涡旋的影响,此时跨隙的西边界流会阻挡中尺度涡旋在缺口处的向西传播,并迫使涡旋在吕宋海峡东侧向北移动.以上结果用来解释了吕宋海峡黑潮变异的某些结构特征.     

利用Argos浮标资料对黑潮入侵南海问题的分析

通过对Argos浮标资料的分析,针对黑潮能否在吕宋海峡入侵南海的问题进行了研究,结果表明:黑潮由吕宋海峡入侵南海主要发生在秋、冬两季,春、夏季基本上不发生。而入侵主要是以流的形式传入,秋季少量的入侵水会有分支沿台湾海峡北上,冬季黑潮自吕宋海峡入侵南海后向西进入南海腹部。并对其季节变化原因作了初步讨论,该区域风应力和黑潮流量的季节性变化可能是重要原因。     

局地风急流对缺口处西边界流流径的影响

基于缺口处的西边界流流态存在迟滞回归现象, 使用1.5 层约化重力浅水模式, 研究了受山脉与地形影响的局地风急流对西边界流流径的影响。结果显示, 在西边界流从跨越态向入侵态转变的临界状态, 局地的西向和南向风应力能够使西边界流向入侵态转变, 局地的东向和北向风应力不能使其发生转变; 在西边界流从入侵态向跨越态转变的临界状态, 除西风以外的风应力都能使西边界流向跨越态转变。此外数值实验还表明风应力旋度的作用强于风应力大小的作用。     

南海北部次表层盐度的变化及其与北赤道流分叉点的关系

吕宋海峡是南海与外界水交换的重要通道,黑潮作为北太平洋最强的1支西边界流,在经过吕宋海峡时会对南海北部的环流和环境产生重要影响。本文用1991—2011年期间CTD断面实测资料和高度计资料,提取23.0~25.5 kg/m³等密度面之间的盐度极大值,研究了南海北部不同年月盐度极大值变化、黑潮入侵方式与强弱,以及盐度极大值变化与北赤道流分叉点南北移动的关系,结果表明:(1)黑潮入侵南海方式多样,既有分支形式,也有弯曲、流套形式。(2)不同年月间,黑潮入侵南海的强弱存在较大差别,120°E断面的次表层盐度极大值的变动可超过0.3。(3)北赤道流分叉点位置的南北变动对黑潮入侵南海的强弱具有重要影响:北赤道流分叉点位置偏北,黑潮入侵南海较强;北赤道流分叉点位置偏南,则黑潮入侵相对较弱。     

源区黑潮研究进展

黑潮(Kuroshio)作为太平洋上一支强大的西边界流,起源于菲律宾以东海域,经吕宋海峡,从台湾以东进入东海,穿越吐噶喇海峡进入日本以南海域,最后汇入北太平洋环流。本文作者所指源区是从菲律宾的吕宋岛以东至我国台湾岛以东之间,在此区域黑潮流经吕宋海峡,流态发生显著变化,是近几年来各国学者研究的重点。关于菲律宾以东黑潮的研究较少,作者重点阐述吕宋海峡处和台湾以东黑潮的研究进展。一、吕宋海峡处黑潮吕宋海峡由巴士海峡、巴林塘海峡和巴布延海峡三个海峡组成。该区属于副热带海洋性气候,具有明显的季风特点。吕宋海峡靠近台湾一侧的…     

基于拉格朗日拟序结构的吕宋海峡表层水交换研究

黑潮通过吕宋海峡入侵南海呈现明显的瞬态特征。以往的研究通常将黑潮在吕宋海峡附近的流态分为几种不同类型。本文基于表层地转流计算得到的有限时间李雅普诺夫指数场（FTLE），展示了拉格朗日视角下的吕宋海峡上层水交换特征。从FTLE场提取的拉格朗日拟序结构（LCSs）很好地识别了吕宋海峡附近的典型流态和旋涡活动。此外，这些LCSs还揭示了吕宋海峡周围复杂的输运路径和流体域，这些特征得到了卫星跟踪浮标轨迹的验证，且从流速场中是无法直接识别的。FTLE场显示，吕宋海峡附近表层水体的输运形态主要可分为四类。其中，黑潮直接向北流动的“跨越”形态和顺时针旋转的“流套”形态的发生频次明显高于直接进入南海的黑潮分支“渗入”形态和南海水流出至太平洋的“外流”形态。本文还进一步分析了黑潮在吕宋海峡处的涡旋脱落事件，突出强调了LCSs在评估涡旋输运方面的重要性。反气旋涡旋的脱落个例表明，这些涡旋主要源自黑潮“流套”，涡旋脱落之前可有效地俘获黑潮水。LCS所指示的输运通道信息有助于预测最终被反气旋涡所挟卷水体在上游的位置。而在气旋涡的形成过程中，LCS的分布特征表明，大部分气旋涡并未与黑潮水的输运路径相连通。因此，气旋涡对从太平洋到南海的上层水交换的贡献较小。     

周期性的或伴有贯穿流的西边界流跨隙流动的迟滞变异过程

使用1.5层准地转约化重力模式研究了周期性的或伴有贯穿流的西边界流跨隙流动的迟滞变异过程。当西边界流变化的周期比罗斯贝波在缺口处调整的时间尺度大得多时，在雷诺数增加和减少过程的霍夫分叉点都发生延迟，从而产生新的雷诺数迟滞区间；并且西边界流流态转变的临界值变化显著；且周期强迫越短，雷诺数迟滞区间越大。当西边界流变化的周期与罗斯贝波在缺口处调整的时间尺度相当时，西边界流在缺口的流态呈无迟滞的周期性变化，且西边界流入侵西海盆的程度随周期减少而变小。此外，当贯穿流的流量大于西边界流的一半时，会显著影响西边界流在缺口处的迟滞变异过程；西边界流向西入侵程度和流态转变发生的临界雷诺值均发生变化，且贯穿流流量越大变化越大。     

黑潮在吕宋海峡的形变及动力机制

根据１９９０年以来对吕宋海峡和中国南海（ＳＣＳ）北部的ＷＯＣＥ水文资料和其它海洋调查资料的分析，以及对同一海区的卫星遥测海表温度（ＳＳＴ）的资料处理，推断在吕宋海峡常年存在黑潮路径弯曲，西折进入ＳＣＳ并又流出ＳＣＳ的现象，作者将黑潮的这种变形称为“黑潮流套”。黑潮变形进入ＳＣＳ的位置在冬季位于海峡中部、南部附近，范围较大；在夏季略向北移，较集中于海峡中部，范围较小。作者认为，黑潮流套现象可用位涡守恒理论作定性的解释：当黑潮在吕宋海峡失去西边界支持后，其流轴以西贴近西边界的一部分流体，因具有较大的相对正涡度，会脱离黑潮主体在南海东北部形成反时针旋转或顺时针旋转的环流，而黑潮主体会以顺时针旋转的形式在海峡以西的海域出现。整个黑潮以弯曲、扩展的形式在海峡处产生形变，在海峡东侧出现反气旋涡旋的倾向。吕宋海峡黑潮流套及南海北部的诱生环流之流型，会因黑潮本身以及副热带环流整体的变化而变化，也与海峡的宽度有关。总之，吕宋海峡黑潮流套的形成是由当地特殊的地形条件和地转β效应这些内部机制决定的，它的常年存在有其必然性     

混合坐标模式HYCOM模拟COADS强迫下的南海平均环流

采用混合坐标模式(HYCOM)模拟南海环流,同时利用海表温度卫星资料和吕宋海峡Sb-ADCP观测海流数据来评估模式结果.地形敏感性实验表明,吕宋海峡地形数据对模拟黑潮入侵方式影响较大,在地形误差较大的情况下,模拟的黑潮可能以反气旋流套方式入侵.和Pathfinder海表温度卫星资料比较,模式输出的月平均温度在海盆区域误差较小.ERA-15资料强迫所模拟的吕宋海峡上层环流和Sb-ADCP观测一致,而COADS结果低估了吕宋海峡的体积输送.     

入侵南海的黑潮流套及其脱落涡旋

将2003年、2004年和2005年秋、冬季在吕宋海峡投放的卫星跟踪漂流浮标(Argos)资料用于分析黑潮通过吕宋海峡时的流型。结果表明,秋、冬季黑潮表层流存在3种类型:北向型、西向型和流套-涡旋型,后两种入侵南海。统计分析指出吕宋海峡表层流进入流套-涡旋型路径的概率为0.23,黑潮流套的纬向尺度最大达210km,仅发生在恒春海脊西侧的台湾岛西南海域。黑潮流套仅是黑潮流分离的一部分,而非黑潮整体蛇形入侵南海,这与墨西哥湾的蛇形流不一样。在流套内西向流速大于东向流速,这可能是流套西向发展的原因之一,黑潮流套常可演变成脱落涡旋,也可能就地消亡。脱落涡旋以约10cm/s速度西移。     

Wind-induced Kuroshio intrusion into the South China Sea

The Kuroshio flows north along the east coasts of the Philippines and Taiwan. Between these two land masses lies the Luzon Strait which connects the Pacific Ocean to the South China Sea. The Kuroshio usually flows north past this strait, but at times part or all of it flows west through the strait into the South China Sea forming a loop current. It has been suggested that the loop current forms when the northeast monsoon deflects the Kuroshio through the Luzon Strait. In this study, satellite-derived sea-surface temperature images are used to observe the Kuroshio in the Luzon Strait region. Together with wind data from the region, these observations indicate a loop-current development process which is largely determined by an integrated supercritical wind stress parameter. The loop current grows when a four-day average of the local wind-stress component directed to the south exceeds 0.08 Nm^–2. When this average wind-stress component drops below the critical value, the Kuroshio returns to its northward path.     

A numerical study of the summertime flow around the Luzon Strait

Luzon Strait, a wide channel between Taiwan and Luzon islands, connects the northern South China Sea and the Philippine Sea. The Kuroshio, South China Sea gyre, monsoon and local topography influence circulation in the Luzon Strait area. In addition, the fact that the South China Sea is a fairly isolated basin accounts for why its water property differs markedly from the Kuroshio water east of Luzon. This work applies a numerical model to examine the influence of the difference in the vertical stratification between the South China Sea and Kuroshio waters on the loop current of Kuroshio in the Luzon Strait during summer. According to model results, the loop current’s strength in the strait reduces as the strongly stratified South China Sea water is driven northward by the southwest winds. Numerical results also indicate that Kuroshio is separated by a nearly meridional ridge east of Luzon Strait. The two velocity core structures of Kuroshio can also be observed in eastern Taiwan. Moreover, the water flowing from the South China Sea contributes primarily to the near shore core of Kuroshio.     

A numerical study of the South China Sea deep circulation and its relation to the Luzon Strait transport

A fine-resolution MOM code is used to study the South China Sea basin-scale circulationand its relation to the mass transport through the Luzon Strait. The model domain includes the South China Sea, part of the East China Sea, and part of the Philippine Sea so that the currents in the vicinity of the Luzon Strait are free to evolve. In addition, all channels between the South China Sea and the Indonesian seas are closed so that the focus is on the Luzon Strait transport. The model is driven by specified Philippine Sea currents and by surface heat and salt flux conditions. For simplicity, no wind-stress is applied at the surface.The simulated Luzon Strait transport and the South China Sea circulation feature a sandwich vertical structure from the surface to the bottom. The Philippine Sea water is simulated to enter the South China Sea at the surface and in the deep ocean and is carried to the southern basin by western boundary currents. At the intermediate depth, the net Luzon Strait transport is out of t     

The variability of internal tides in the Northern South China Sea

An array of three bottom-mounted ADCP moorings was deployed on the prevailing propagation path of strong internal tides for nearly 1 year across the continental slope in the northern South China Sea. These velocity measurements are used to study the intra-annual variability of diurnal and semidiurnal internal tidal energy in the region. A numerical model, the Luzon Strait Ocean Nowcast/Forecast System developed at the U.S. Naval Research Laboratory that covers the northern South China Sea and the Kuroshio, is used to interpret the observed variation of internal tidal energy on the Dongsha slope. Internal tides are generated primarily at the two submarine ridges in the Luzon Strait. At the western ridge generation site, the westward energy flux of the diurnal internal tide is sensitive to the stratification and isopycnal slope associated with the Kuroshio. The horizontal shear at the Kuroshio front does not modify the propagation path of either diurnal or semidiurnal tides because the relative vorticity of the Kuroshio in Luzon Strait is not strong enough to increase the effective inertial frequency to the intrinsic frequency of the internal tides. The variation of internal tidal energy on the continental slope and Dongsha plateau can be attributed to the variation in tidal beam propagation in the northern South China Sea.     

Intrusion of the Kuroshio into the South China Sea,in September 2008

Using widespread conductivity–temperature–depth (CTD) data in the Philippine Sea and northern South China Sea near the Luzon Strait together with altimeter data, we identified an intrusion of water from the Kuroshio into the South China Sea (SCS) through the Luzon Strait in September 2008. The Kuroshio water obviously intruded into the SCS from 20 to 21°N, and existed mainly in the upper 300 m. The intrusion water extended as far west as 117°E, then looped around in an anticyclonic eddy and returned to the Philippine Sea further north. The dynamics of the Kuroshio intrusion are discussed using a 1.5-layer nonlinear shallow-water reduced-gravity model. The analysis suggests that the strong cyclonic eddy to the east of the Kuroshio in September 2008 was of benefit to the intrusion event.     

基于卫星高度计资料的黑潮入侵南海流径的时间变化规律研究

黑潮入侵南海对南海的温盐平衡、环流、涡旋和局地气候等具有重要作用。基于吕宋海峡处黑潮不同流径的识别方法,对1993～2021年的卫星高度计资料进行识别,获取黑潮不同流径的发生时间,探究黑潮入侵南海流径的时间变化规律。结果表明:(1)黑潮主要以流套(Looping)和分支(Leaking)两种流径入侵南海,Leaking流径发生的时长(710周)和概率(46.9%)要远高于Looping流径(时长218周,概率14.4%)。(2) Looping流径和Leaking流径均可将高温高盐的西北太平洋水带入南海,Looping流径下的平均吕宋海峡上层通量(6.3×10⁶ m³/s)略大于Leaking流径(5.6×10⁶ m³/s)Looping和Leaking流径在4×10⁶ m³/s～6×10⁶ m³/s区间发生时间最长。(3)季节变化上,Looping流径主要发生在冬季,Leaking流径在冬半年均较强,夏季二者发...     

南海东北部叶绿素a浓度对台风“风泵”和黑潮共同作用的响应

南海东北部是寡营养海域，夏季浮游植物叶绿素浓度较低，热带气旋“风泵”效应带来的上层海洋扰动可能引起表层浮游植物的显著增长。以往的研究通常关注热带气旋风应力和海洋中尺度涡对上层海洋浮游植物的影响，本文利用航次CTD、实测叶绿素a浓度、Argo温盐剖面和遥感数据，探讨了台风“风泵”和黑潮共同作用下真光层内浮游植物的变化特征及其成因。结果表明，2015年台风“莲花”过境1周后产生向吕宋海峡西北侧南海海域(A区)入侵的黑潮流套，该入侵的黑潮流套使台风前原有的气旋涡消失，抑制了台风产生的上升流对表层(0～40 m)营养盐供给，使次表层(60～90 m)营养盐富集，进而抑制了表层的叶绿素a增长，促进了次表层叶绿素a的增长；吕宋海峡西侧南海海域(B区)表层的浮游植物叶绿素a浓度增加不仅是源于叶绿素最大层浮游植物的向上输运，更是由于浮游植物的繁殖增长；A区台风引起的流套式的黑潮入侵，促进了B区台风后气旋式流场的形成，产生的持续增强的气旋涡为B区表层叶绿素持续增长提供了充足的营养盐供给。     

Circulation of the East China Sea,a numerical study

A three-dimensional, primitive-equation model is developed to study how the Kuroshio, the monsoon, the Yangtze River outflow and the buoyancy forcing from the South China Sea affect the circulation of the East China Sea. It is found that the Kuroshio water usually intrudes into the East China Sea from both sides of Taiwan Island. Winter winds enhance the Kuroshio intrusion from northeast of Taiwan, but weaken it from the Taiwan Strait. Summer winds act in the opposite way. The increased presence of the Kuroshio water in the East China Sea in winter can be largely attributed to the shoreward surface Ekman drift associated with the northerly wind. In summer, the-shaped plume emanating from the Taiwan Strait is, to a large extent, produced by the buoyancy forcing from the South China Sea.In summer, the bimodal distribution of the Yangtze River outflow is initially produced by the upwelling-favorable wind. Away from the Yangtze River, the far-field dispersal of the fresher water depends on the strength of the Kuroshio. A stronger Kuroshio enhances the seaward dispersal of the northern branch of the Yangtze outflow north of Taiwan, but reduces the southward penetration of the southern branch. In winter, downwelling-favorable winds confine the Yangtze River outflow to a narrow band forming nearshore coastal jet penetrating southward. The northern tip of Taiwan acts as a conduit, channeling the seaward dispersal of the fresher water. The model results interpret the observed circulation patterns.     

A high-resolution numerical modeling study of the subtidal circulation in the northern South China Sea

A high-resolution, regional, numerical-model-based, real-time ocean prediction system for the northern South China Sea, called the Northern South China Sea Nowcast/Forecast System (NSCSNFS), has been used to investigate subtidal mesoscale flows during the time period of the Asian Seas International Acoustic Experiment (ASIAEX) field programs. The dynamics are dominated by three influences; 1) surface wind stress, 2) intrusions of the Kuroshio through Luzon Strait, and 3) the large-scale cyclonic gyre that occupies much of the northern South China Sea. Each component primarily drives currents in the upper ocean, so deep currents are rather weak. Wind stress is especially effective at forcing currents over the shallow China shelf. The Kuroshio intrusion tends to flow westward until it meets the northern edge of the large-scale cyclonic gyre. Together, these currents produce an intense, narrow jet directed northwest toward the continental slope, often in the region of the ASIAEX field programs. Upon reaching the slope, the current splits with part flowing northeastward along the slope and part flowing southwestward, producing large horizontal and vertical shears and making this region dynamically very complicated and difficult to simulate. The Kuroshio intrusion tends to be stronger (weaker) when the northeasterly winds are strong (weak) and the large-scale gyre is farther south (north), consistent with conclusions from previous model studies. At the northern boundary, the model produces a persistent northward flow through Taiwan Strait into the East China Sea. Data assimilation in the NSCSNFS model is shown to dampen the system, extracting energy and causing the entire system to spin down.     

1998年春夏南海温盐结构及其变化特征

利用1998年5～8月“南海季风试验”期间“科学1”号和“实验3”号科学考察船两个航次CTD资料,分析了1998年南海夏季风暴发前后南海主要断面的温盐结构及其变化特征.观测发现,南海腹地基本被典型的南海水团所控制,但在南海东北部尤其是吕宋海峡附近,表层和次表层水明显受到西太平洋水的影响.季风暴发以后,南海北部表面温度有显著升高,升幅由西向东递减,而南海中部和南部表面温度基本没变,这使得南海北部东西向温度梯度和整个海盆南北向温度梯度均减小.北部断面表层盐度普遍由34以上降低到34以下,混合层均有所发展,是季风暴发后降水和风力加剧的结果.观测期间黑潮水跨越吕宋海峡的迹象明显但变化剧烈.4～5月,黑潮次表层水除在吕宋海峡中北部出现外,在吕宋岛以西亦有发现,表明有部分黑潮水从吕宋海峡南端沿岸向西进而向南进入南海.6～7月,次表层高盐核在吕宋海峡中北部有极大发展,但在吕宋岛以西却明显萎缩;虽然看上去黑潮水以更强的流速进、出南海,但对南海腹地动力热力结构的影响未必更大.一个超过34.55的表层高盐水体于巴拉望附近被发现,似与通过巴拉望两侧水道入侵南海的西太平洋水有关.