Three-dimensional calculations of the currents in the Huanghai Sea and East China Sea during June of 1999

Based on the wind and hydrographic data obtained by R/V Xiangyanghong 14 duringJune of 1999, the currents in the Huanghai Sea and East China Sea are computed by the three dimen-sional non-linear diagnostic, semidiagnostic models and prognostic in the σ coordinate. The computed re-sults show that the density and velocity fields and so on have been adjusted when time is about 3 days,namely the solution of semidiagnostic calculation is obtained. In the northwest part of the computed re-gion, the Huanghai coastal current flows southeastward, and then it flows out the computed region southof Cheju Island. In the west side of the southern part of the computed region, there is other current,which is mainly inshore branch of Taiwan Warm Current, and it flows cyclonically and turns to thenortheast. In the region north of the above two currents, there is a cyclonic eddy southwest of Cheju Is-land, and it has characteristics of high density and low temperature. There is an offshore branch of Tai-wan Warm Current in the west side of the Kuroshio, and it makes a cyclonic meander, then flows north-eastward. The Kuroshio in the East China Sea is stronger, and flows northeastward. Its maximum hori-zontal velocity is 108.5 cm/s at the sea surface, which is located at the northern boundary, and it is106.1 cm/s at 30 m level, 102.2 cm/s at 75 m level and 85.1 cm/s at 200 m level, respectively, whichare all located at the southern boundary. Comparing the results of diagnostic calculation with those ofsemidiagnostic and prognostic calculations indicates that the horizontal velocity field agrees qualitatively,and there is a little difference between them in quantity. The comparison between the computed veloci-ties and the obeered velocities at the mooring station show that they agree each other.     

Three dimensional diagnostic, semidiagnostic and prognostic calculations of current in the East China Sea in April of 1994

ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｒｅａｒｅｍａｎｙｍｏｄｅｌｓｔｏｃａｌｃｕｌａｔｅｔｈｅｃｕｒｒｅｎｔｓｉｎｔｈｅＥａｓｔＣｈｉｎａＳｅａａｎｄｏｔｈｅｒｎｅｉｇｈｂｏｒ ｉｎｇｓｅａｓ ,ａｎｄｓｏｍｅｏｆｔｈｅｍａｒｅｂｅｉｎｇｍｏｄｉｆｉｅｄａｎｄｄｅｖｅｌｏｐｅｄｗｉｔｈｔｈｅｔｉｍｅ .Ｔｈｅｓｅｍｏｄｅｌｓａｒｅａｓｆｏｌｌｏｗｓ :(1 )ｔｈｅｆｉｎｉｔｅｅｌｅｍｅｎｔｍｅｔｈｏｄ ,ａｎｄａｃｏｍｂｉｎａｔｉｏｎｏｆｆｉｎｉｔｅｅｌｅｍｅｎｔｍｅｔｈｏｄｗｉｔｈｔｈｅａｃｃｕｒａｔｅｓｏｌ…     

Calculation of current in the Taiwan Strait during summer Ⅱ.Three-dimensional semidiagnostic and prognostic calculations

INTRoDUCTIONAdiagnosticmodel(WangandYuan,1997)hasbeenusedtocalculatethecurrentintheTaiwanStrait(TS)duringsummer.Astothesemidiagnosticmodel,SarkisyanandYu(1983)firstlysetupasemidiagnosticmodel,whichisalsocalledanadjustablem0del,andtheyusedittocalculatethecirculati0n0vertheAtlanticOcean.YuanandPan(l995)alsodevelopedathree-di-mensi0nalsemidiagnosticmodelandcalculatedthecirculationovertheEastChinaSea.Theprog-mpticm0dlfortheoceans,whichissimilartothesemidiagnosticmodel,wasstudiedearlierby…     

东海黑潮周边中尺度涡的分布、运动规律以及生成机制

为了探究东海黑潮周边涡旋分布、形成机理及运动规律,基于法国国家空间研究中心(CNES)卫星海洋学存档数据中心(AVISO)的中尺度涡旋数据集展开了研究。首先,统计了近27年东海黑潮周边的涡旋分布,发现在黑潮弯曲海域产生了650个涡旋,在黑潮中段海域产生了271个涡旋,其中直径100~150 km之间的涡旋数量最多,涡旋振幅主要集中在2~6 cm。其次,分析了东海黑潮的运动路径和涡运动过程,结果表明,黑潮气旋式弯曲海域内侧易产生气旋涡,且移动路径较长,如台湾东北海域黑潮流轴气旋式弯曲处产生的涡旋,其平均位移达到了87.6 km;当反气旋式弯曲海域内侧产生反气旋涡时,涡旋往往做徘徊运动。黑潮中段海域的涡旋呈现出气旋涡在黑潮主轴西侧、反气旋涡在黑潮主轴东侧的极性对称分布特征,两类涡都沿黑潮主轴向东北方向移动。最后,结合再分析的流场、海面高度数据,讨论了涡旋运动规律和生成机制。黑潮弯曲处涡旋的生成与黑潮流体边界层分离有关,奄美大岛南部到冲绳岛西侧的黑潮逆流对黑潮中段海域涡的极性对称分布起到了关键作用,涡旋在运动过程中通常经历生长、成熟和衰变三个阶段。     

中国近海及其附近海域若干涡旋研究综述Ⅱ.东海和琉球群岛以东海域

综述东海和琉球群岛以东海域若干气旋型和反气旋型涡旋的研究.对东海陆架、200m以浅海域,主要讨论了东海西南部反气旋涡、济州岛西南气旋式涡和长江口东北气旋式冷涡.东海两侧和陆坡附近出现了各种不同尺度的涡旋,其动力原因之一是与东海黑潮弯曲现象有很大关系,其次也与地形、琉球群岛存在等有关.东海黑潮有两种类型弯曲:黑潮锋弯曲和黑潮路径弯曲.黑潮第一种弯曲出现了锋面涡旋,评述了锋面涡旋的存在时间尺度与空间尺度和结构等;也指出了黑潮第二种弯曲,即路径弯曲时在其两侧出现了中尺度气旋式和反气旋涡,讨论了它们的变化的特性.特别讨论了冲绳北段黑潮弯曲路径和中尺度涡的相互作用,着重指出,当气旋式涡在冲绳海槽北段成长,并充分地发展,其周期约在1~3个月时,它的空间尺度成长到约为200km(此尺度相当于冲绳海槽的纬向尺度)时,黑潮路径从北段转移到南段.也分析了东海黑潮流量和其附近中尺度涡的相互作用.最后指出在琉球群岛以东、以南海域,经常出现各种不同的中尺度反气旋式和气旋式涡,讨论了它们在时间与空间尺度上变化的特征.     

南海东北部及台湾海峡附近环流的一个耦合模式Ⅰ.模式的建立及背景

通过对南海东北部及台湾海峡邻近海域环流产生影响的各个动力因子进行量级分析,在Hurlburt等人数值模式的基础上,建立起分区性的正压、斜压耦合模式,以便能反映大陆架、大陆坡变化剧烈的底形效应对边缘海环流的影响。将该模式用于南海东北部及台湾海峡附近环流的数值研究。初步的试验计算结果表明,耦合模式能克服两层模式易发生"交面"和"交底"等现象的缺点,同时能反映斜压效应及底形效应的影响,使模拟的计算结果更切合实际,即：（1）黑潮通过巴士海峡侵入南海海域,并导致东沙群岛附近终年存在一个气旋涡;（2）台湾海峡西南海域的大陆架－大陆坡底形效应十分重要;（3）海水在台湾海峡的流动基本上为N向流动,流量约为2×10~6m~3·s-1;（4）模式中有类似于南海暖流的海流出现。     

The Kuroshio east of Taiwan and the currents east of the Ryūkūy-guntōduring October of 1995

On the basis of hydrographic data obtained during two October cruises of 1995, a modified inverse method is used to compute the Kuroshio east of Taiwan and the currents east of the Ryukyu-gunto.The net northward volume transport(VT) of the Kuroshio through Section TK₂-K₂ southeast of Taiwan is about 57.8×10⁶ m³/s.There are four current cores of the Kuroshio at Section TK₂-K₂.Its main core is near the south of Taiwan, and its maximum speed is about 257 cm/s at the surface.After the Kuroshio flows through Section TK₂-K₂, there are three branches of the Kuroshio.The main branch of the Kuroshio flows northward into Section TKa east of Su''ao.The second branch of the Kuroshio flows northward through Section TKa and then enters the East China Sea through the region between Yonakunijima and Iriomote-shima.The net northward VT of the Kuroshio through Section TK4 is about 21.6×10⁶ m³/s.The eastern branch of the Kuroshio flows northeastward through the region between a stronger cyclonic eddy and a recirculating anticyclonic gyre, and then flows continuously northeastward to the region east of the Ryūkyū-guntō and becomes a part of the origin of the western boundary current east of the Ryūkyū-guntō.Another part of the origin of the western boundary current east of the Ryūkyū-guntō comes from a recirculating anticyclonic gyre.From the above, in the regions east of Taiwan end east of the Ryūkyū-guntō the pattern of circulation during October of 1995 differs from the pattern of circulation during early summer of 1985.There are several eddies of different scales in this computational region.For example, there is a meso-scale stronger cyclonic eddy whose center is located at about 23°N, 124°20''E.     

吕宋和台湾岛以东黑潮季节与年际变化规律的对比分析

黑潮是北太平洋副热带环流系统的一支重要的西边界流。前人对不同流段黑潮的季节和年际变化进行了诸多研究,然而基于不同数据所得结论仍存在差异,尤其是不同模式计算所得流量差别很大,而且以往研究往往着眼于某一流段,对不同流段黑潮变化之间的异同及其原因涉及较少。本文基于卫星高度计数据,评估了OFES(Ocean generalcir culation model For the Earth Simulator)和HYCOM(Hybrid Coordinate Ocean Model)两个模式对吕宋岛和台湾岛以东黑潮季节与年际变化的模拟能力,进而对两个海域黑潮变化的异同及其物理机制进行了分析。结果表明:HYCOM模式对黑潮季节变化的模拟较好,而OFES模式对黑潮年际变化的模拟较好。吕宋岛以东黑潮和台湾岛以东黑潮在季节与年际尺度上的变化规律均不相同,且受不同动力过程控制。吕宋岛以东黑潮呈现冬春季强而秋季弱的变化规律,主要受北赤道流分叉南北移动的影响;而台湾岛以东黑潮呈现夏季强冬季弱的变化特点,主要受该海区反气旋涡与气旋涡相对数目的季节变化影响。在年际尺度上,吕宋岛以东黑潮与北赤道流分叉及风应力旋度呈负相关,当风应力旋度超前于流量4个月时相关系数达到了-0.56;而台湾岛以东黑潮的流量变化则受制于副热带逆流区涡动能的变化,且滞后于涡动能9个月时达到最大正相关,相关系数为0.44。本研究对于深入理解不同流段黑潮的多尺度变异规律及其对邻近海区环流与气候的影响具有重要意义,同时对于黑潮研究的数值模式选取具有重要参考价值。     

台湾以东中尺度涡对黑潮入侵东海路径的影响

利用AVISO数据集的卫星高度计资料,分析了中国台湾以东中尺度涡的时空特征,通过具体的中尺度涡实例探讨了其对台湾以东黑潮路径的影响。研究表明气旋式中尺度涡在春夏季节的数目要少于反气旋式中尺度涡,在秋冬季节气旋式涡旋个数则多于反气旋涡;并且台东以东区域涡旋传播存在多种路径,涡旋的存在对台湾东北部黑潮入侵东海的路径具有重大影响,特别是2004年夏季台湾以东区域存在多个涡旋,相应的吕宋海峡黑潮主轴向东偏移明显,台湾东北黑潮入侵东海的路径发生了显著变化。     

Influence of Mesoscale Eddies on Variations of the Kuroshio Path South of Japan

The influences of mesoscale eddies on variations of the Kuroshio path south of Japan have been investigated using time series of the Kuroshio axis location and altimeter-derived sea surface height maps for a period of seven years from 1993 to 1999, when the Kuroshio followed its non-large meander path. It was found that both the cyclonic and anticyclonic eddies may interact with the Kuroshio and trigger short-term meanders of the Kuroshio path, although not all eddies that approached or collided with the Kuroshio formed meanders. An anticyclonic eddy that revolves clockwise in a region south of Shikoku and Cape Shionomisaki with a period of about 5–6 months was found to propagate westward along about 30°N and collide with the Kuroshio in the east of Kyushu or south of Shikoku. This collision sometimes triggers meanders which propagate over the whole region south of Japan. The eddy was advected downstream, generating a meander on the downstream side to the east of Cape Shionomisaki. After the eddy passed Cape Shionomisaki, it detached from the Kuroshio and started to move westward again. Sometimes the eddy merges with other anticyclonic eddies traveling from the east. Coalescence of cyclonic eddies, which are also generated in the Kuroshio Extension region and propagate westward in the Kuroshio recirculation region south of Japan, into the Kuroshio in the east of Kyushu, also triggers meanders which mainly propagate only in a region west of Cape Shionomisaki. This revised version was published online in July 2006 with corrections to the Cover Date.     

琉球群岛附近海域中尺度涡的初步研究

采用1977年1月至2006年12月高分辨率全球大洋环流模型OFES输出结果对琉球群岛附近海域的中尺度涡进行了研究分析。结果表明:(1)尺度较大的涡旋的分布密集区主要有台湾以东海域、琉球海沟上层海域和四国以南海域。(2)琉球海流流经海域的反气旋涡旋占优势,有利于琉球海流的发展。(3)琉球海流受中尺度涡的影响十分显著,纬度越低,其受中尺度涡的影响越明显,而黑潮相对比较稳定,受中尺度涡的影响并不显著。(4)四国以南海域暖涡从黑潮脱落之后向西南移动,该涡旋的移动对琉球海流和黑潮产生特别显著的影响。文章的最后还讨论了中尺度涡与黑潮弯曲以及琉球海流可能存在的联系。     

A case study of a Kuroshio main path cut-off event and impacts on the South China Sea in fall-winter 2013–2014

This study examines a Kuroshio main path(KMP) cut-off event east of Taiwan Island occurred in fall-winter2013–2014 and its impacts on the South China Sea(SCS) by analyzing satellite altimetry and mooring observations. Satellite altimeter sea level anomaly(SLA) images reveal a complete process that a huge cyclonic eddy(CE) from the Pacific collided with the Kuroshio and the western boundary from 15 October 2013 to 15 January 2014. Mooring observations evidenced that the Kuroshio upper ocean volume transport was cut off more than 82% from 17×106 m~3/s in September to 3×106 m~3/s in November 2013. The KMP cut-off event caused the Kuroshio branching and intruding into the SCS and strengthened the eddy kinetic energy in the northern SCS west of the Luzon Strait. Using the total momentum as a dynamic criterion to determine the role of eddy collision with the Kuroshio reasonably explains the KMP cut-off event.     

台湾以东黑潮的低频变化及机制研究

本文基于AVISO（Archiving, Validation and Interpretation of Satellite Oceanographic data）1993-2015年间的海表面绝对动力高度数据,研究了台湾以东黑潮的低频变化特征,并探讨了影响其变化的机制。结果表明,台湾以东多年平均的黑潮流幅值约为136 km,表层流量值约为7.75×104 m2/s,对应的标准差分别为28 km和2.14×104 m2/s。台湾以东黑潮不仅具有显著的季节变化特征,还具有显著的年际变化特征。功率谱分析结果表明,台湾以东黑潮表层流量具有1 a和2.8 a的显著周期。空间上,台湾东南部黑潮的年际变化幅度比东北部强烈。相关性及合成分析结果表明,台湾以东黑潮的年际变化与PTO（Philippines-Taiwan Oscillation）之间存在显著的相关性。PTO年际震荡所导致的副热带逆流区反气旋式涡旋与气旋式涡旋的相对强度是影响台湾以东黑潮年际变化的主要动力因素。     

台湾以东表面黑潮流量与涡旋场相互作用研究

本文基于法国空间局AVISO中心提供的1993年~2015年的卫星遥感海面高度和海表流场逐日资料,分析了台湾以东表面黑潮流量及其邻近海域的涡旋场（海面高度异常）,得到了台湾以东表面黑潮流量和涡旋场的四个主要周期,并研究了不同对应周期的黑潮表面流量及其邻近涡旋场之间的相互作用关系。论文主要结论如下：（1）基于小波分析法,分析了台湾以东表面黑潮流量及其邻近的涡旋场,发现两者都具有明显的季节、年和年际变化周期。对于表面黑潮流量,除了具有182天（0.5年）和365天（1年）的显著周期外,还存在860天（2.35年）和2472天（6.8年）左右的较为明显的周期。涡旋场也相应地存在200天（0.55年）、374天（1年）、889天（2.43年）和2374天（6.5年）四个较明显的周期,但在不同的纬度存在一定差异;（2）基于相关分析和因果分析法,分析了以上四个周期内表面黑潮流量及其邻近涡旋场的相关性,揭示了黑潮与涡旋在不同周期区间、不同纬度相互影响关系的差异。     

Taiwan Current (Kuroshio) and Impinging Eddies

Considerable westward or nothwestward propagating eddies were found east of Taiwan that cross-explains the anomalies in the repeated hydrography, trajectory of drifting buoys and altimetric analyses. The sea level differences (SLD) across the Taiwan Current (Kuroshio) in the East Taiwan Channel (ETC) are utilized in order to examine the possible implication of eddies in the Taiwan Current transport. It is concluded that Taiwan is impinged by both cyclonic and anticyclonic mesoscale eddies at an interval of about 100 days. An approaching anticyclonic eddy will result in a higher SLD across the ETC and a larger mass transport of Taiwan Current, and, vice versa, a reduction of both SLD and the mass transport in the ETC as a cyclonic eddy arrives. The SLD-inferred northward transport in the ETC is highly coherent at the 100-day band with westward propagating eddies that originated in the interior ocean. The generation mechanism of these eddies are, however, still unclear. Leakage of the Kuroshio water to the east of the Ryukyu Islands is suggested due to the presence of cyclonic eddies. This 100-day rate of eddy-impingement invalidates any observation of 4 months or less, whether with direct or indirect measurements, because any conclusions depend on the presence or absence of eddies. To minimize the contamination from eddies, either long-term observations or eddy-removal procedures are required.     

1995与1996年夏季琉球群岛两侧海流

基于1995,1996年夏季日本调查船的观测资料,采用P矢量方法对琉球群岛两侧的海流进行了计算.结果表明:黑潮为琉球群岛以西海域的一支东北向强流,1996年夏季的流速比1995年夏季的强,在深层出现南向逆流.黑潮东、西两侧分别存在一个反气旋式暖涡和一个弱的气旋式冷涡.1995年夏季,琉球群岛以东,从表层至以下层都存在一支沿岸北上的海流,即琉球海流.该海流来自黑潮分支,为本海区的一个主要物理特征.琉球海流以下出现弱的南向流.冲绳岛以东海域,在25°～25°30'N,128°30'～129°10'E附近从表层至700m水深存在一个中尺度的反气旋式暖涡.在温、盐水平分布图上,对应的出现一个较高温、低密水块.1996年夏季,冲绳岛西南海域存在一个中尺度的反气旋式暖涡和一个气旋式冷涡,形成一个偶极子,中间为较强的南向流,该现象为本海区的一个重要物理特征,属首次报道.冲绳岛以东表层主要被南向流控制,琉球海流不明显.200m以深在近岸出现北向流,这表明琉球海流的核心位于次表层.琉球海流的下面出现南向流.计算海区东北部从表层到700m水深出现一个中尺度的反气旋式暖涡,与1995年夏季时比较,其位置向北移动.此外在1996年夏季从近表层到深层,垂直方向和水平方向上的等温线、等盐线波动很大,例如在C断面上冷、暖涡相间出现,且暖     

Anticyclonic Eddy Revealing Low Sea Surface Temperature in the Sea South of Japan: Case Study of the Eddy Observed in 1999–2000

Various kinds of datasets, such as satellite-derived sea surface temperature (SST), sea surface height, surface velocity produced by combining surface drifter and satellite altimeter data, and hydrographic data, led to the discovery of an anticyclonic eddy with lower SST than those of surrounding waters in the Kuroshio recirculation region south of Shikoku, as if the eddy were cyclonic. This anticyclonic eddy was formed east of Kyushu in late August to early September 1999 from the merger of two anticyclonic eddies which had migrated in the recirculation region to the sea south of Japan from the east. After the merger, the anticyclonic eddy strengthened abruptly and began to exhibit the low SST. In October, this eddy coalesced with the Kuroshio and moved swiftly eastward, accompanied by an amplitude growth of the Kuroshio meander. In mid November, off the Kii Peninsula, the eddy detached from the meandering Kuroshio. It then moved southwestward and again slowly propagated westward along the 30°N line. During this period, at least from late October 1999 to January 2000, SSTs over the anticyclonic eddy were found to be continuously lower than those of surrounding waters. This case tells us that we have to pay careful attention to the interpretation of mesoscale SST distributions. This revised version was published online in July 2006 with corrections to the Cover Date.     

Primary Study of the Mechanism of Eddy Shedding from the Kuroshio Bend in Luzon Strait

The mechanism of the anticyclonic eddy's shedding from the Kuroshio bend in Luzon Strait has been studied using a nonlinear 2 1/2 layer model, in a domain including the North Pacific and South China Sea. The model is forced by steady zonal wind in the North Pacific. Energy analysis is adopted to detect the mechanism of the eddy shedding. Twelve experiments with unique changes of wind forcing speed (to obtain different Kuroshio transports at Luzon Strait) were performed to examine the relationship between the Kuroshio transport (KT) and the eddy shedding events. In the reference experiment with KT of 22.7 Sv (forced with zonal wind idealized from the annual mean wind stress from the COADS data set), the interval of eddy shedding is 70 days and the shed eddy centers at (20°N, 117.5°E). When the Kuroshio bend extends westward, the southern cyclonic perturbation grows so rapidly as to form a cyclonic eddy (18.5°N, 120.5°E) because of the frontal instability in the south of the Kuroshio bend. In the evolution of the cyclonic eddy, it cleaves the Kuroshio bend and triggers the separation of the anticyclonic eddy. In statistical terms, anticyclonic eddy shedding occurs only when KT fluctuates within a moderate range, between 21 Sv and 28 Sv. When the KT is larger than 28 Sv, a stronger frontal instability south of the Kuroshio bend tends to generate a cyclonic eddy of size similar to the width of the Luzon Strait. The bigger cyclonic eddy prevents the Kuroshio bend from extending into the SCS and does not lead to eddy shedding. On the other hand, when the KT decreases to less than 21 Sv, the frontal instability south of the Kuroshio bend is so weak that the size of corresponding cyclonic eddy is smaller than half the width of the Luzon Strait. The cyclonic eddy, lacking power, fails to cleave the Kuroshio bend and cause separation of an anticyclonic eddy; as a result, no eddy shedding occurred then, either.     

中国近海及其附近海域若干涡旋研究综述 Ⅰ.南海和台湾以东海域

综述了南海和台湾以东海域若干气旋型和反气旋型涡旋研究.在南海存在着许多活跃的中尺度涡,我们分别对南海中、南部海域和南海北部海域中尺度涡作了评述.在南海北部海域,目前最感兴趣的问题为:南海水与西菲律宾海通过吕宋海峡的交换的物理过程,以及黑潮是否以反气旋流套形式进入南海.这些问题目前尚不清楚,尤其是这些问题的机理.这些问题必须通过今后深入和细致的、长时间的海流和水文观测,以及长时间卫星遥感观测资料的论证才能逐渐认识清楚.台湾以东海域,黑潮两侧经常出现中尺度涡,而且变化较大而复杂.文中着重讨论兰屿冷涡和台湾东北的气旋式冷涡.     

环台湾岛海域冬季水文要素的数值模拟

本文利用POM模式对环台湾岛海域冬季的水文要素进行了数值模拟,对有代表性的水平环流、温度场和上升流三个要素所进行的分析表明:模式再现了台湾岛东岸的高温高盐强流速区即黑潮,黑潮在冬季并无直接进入台湾海峡的分支存在;西岸的东北向流在冬季各个层次上都存在,台湾东北部的冷涡模拟与实况较为一致。温度场和上升流的分布与水平环流有很好的对应关系。本文还进一步验证了前人的一些研究成果,并对一些特殊物理现象的成因进行了定性解释。