Thermal fronts and cross-frontal heat flux in the southern Huanghai Sea and the East China Sea

Synoptic features in/around thermal fronts and cross-frontal heat fluxes in the southern Huanghai./Yellow Sea and East China Sea （HES） were examined using the data collected from four airborne expendable bathythermograph surveys with horizontal approxmately 35 km and vertical 1 m（from the surface to 400 m deep） spacings. Since the fronts are strongly affected by HES current system, the synoptic thermal features in/around them represent the interaction of currents with surrounding water masses. These features can not be obtained from climatological data. The identified thermal features are listed as follows ： （ 1 ） multiple boundaries of cold water, asymmetric thermocline intrusion, locally-split front by homogeneous water of approxmately 18 ℃, and mergence of the front by the Taiwan Warm Current in/around summertime southern Cheju - Changjiang/Yangtze front and Tsushima front; （2） springtime frontal eddy-like feature around Tsushima front; （3） year-round cyclonic meandering and summertime temperature-inversion at the bottom of the surface mixed layer in Cheju - Tsushima front; and （4） multistructure of Kuroshio front. In the Kuroshio front the mean variance of vertical temperature gradient is an order of degree smaller than that in other HES fronts. The southern Cheju- Changjiang front and Cheju -Tsushima front are connected with each other in the summer with comparable cross-frontal temperature gradient. However, cross-frontal heat flux and lateral eddy diffusivity are stronger in the southern Cheju - Changjiang front. The cross-frontal heat exchange is the largest in the mixing zone between the modified Huanghai Sea bottom cold water and the Tsushima Warm Current, which is attributable to enhanced thermocline intrusions.     

Thermal and haline fronts in the Yellow/East China Seas: Surface and subsurface seasonality comparison

Seasonal variability of surface and subsurface thermal/haline fronts in the Yellow/East China Seas (YES) has been investigated using three-dimensional monthly-mean temperature and salinity data from U.S. Navy’s Generalized Digital Environmental Model (Version 3.0). The density-compensated Cheju-Yangtze Thermal/Haline Front has (northern and southern) double-tongues. The northern tongue is most evident throughout the depth from December to April. The southern tongue is persistent at the subsurface with conspicuous haline fronts. The thermal (haline) frontal intensity of the northern tongue is controlled mainly by the temperature (salinity) variation on the shoreward (seaward) side of the front. The cold water over the Yangtze Bank is influential in generating the southern tongue and intensifying the Tsushima Thermal Front. The year-round Cheju-Tsushima Thermal Front is evident throughout the depth and intensifies from July to December. The northern arc of the Yangtze Ring Haline Front is manifest in spring and is sustained until summer, whereas the southern one is fully developed in summer because of eastward migration of the Yangtze Diluted Water. The area showing strong frontal intensity in the Chinese Coastal Haline Front shifts seasonally north and south along the Zhejiang-Fujian coast. The Generation and evolution of YES fronts are closely associated with YES circulation (inferred from the linkage of the water masses). Moreover, the subsurface temperature/salinity evolution on the fronts in the Yellow Sea differs from that in the East China Sea owing to local factors such as wintertime vertical mixing and a summertime strong thermocline above the Yellow Sea Bottom Cold Water.     

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.     

The circulation in the southern Huanghai Sea and northern East China Sea in June 1999

On the basis of hydrographic data and current measurement (the mooring system, vessel-mounted ADCP and toward ADCP) data obtained in June 1999, the circulations in the southern Huang-hai Sea (HS) and northern East China Sea (ECS) are computed by using the modified inverse method. The Kuroshio flows northeastward through eastern part of the investigated region and has the main core at Section PN, a northward flow at the easternmost part of Section PN, a weaker anti-cyclonic eddy between these two northward flows, and a weak cyclonic eddy at the western part of Section PN. The above current structure is one type of the current structures at Section PN in ECS. The net northward volume transport (VT) of the Kuroshio and the offshore branch of Taiwan Warm Current (TWCOB) through Section PN is about 26.2×106m3/s in June 1999. The VT of the inshore branch of Taiwan Warm Current (TWCIB) through the investigated region is about 0.4×106m3/s. The Taiwan Warm Current (TWC) has much effect on the currents over the     

关于黑潮延伸体海域水体的三维热结构时-空变化特征研究

基于西北太平洋Argo数据资料,利用参数化方法,从Argo温盐剖面数据中提取出一系列特征动力参数,定量分析黑潮延伸体海域水体的三维热结构的时-空变化特征、季节变化特征及其与地形和环流的关系。结果表明:黑潮延伸体海域水体的海表面温度存在着明显的冬春弱,夏秋强的季节变化特征,冬季平均海表面温度为15℃,夏季则达到了27℃;混合层深度在春季和夏季都较深,在180 m左右,秋冬较浅,在17 m左右,在水平方向上混合层深度有较强的梯度;温跃层春、夏、秋、冬4季的平均温度表现出明显的南北差异,夏季南部海域平均温度为14℃左右,北部海域较低为5℃左右;季节性温跃层深度大约在100 m左右;黑潮延伸体海域水体的温跃层底部最大深度在800 m左右;黑潮延伸体主体海域中心位置冬天在36°N左右,夏天大约移到34°N。     

Variability of the circulation in the southern Huanghai Sea and East China Sea during the two investigative cruises in June 1999

1IntroductionAlotofworkonthestudyofthecircula-tionintheHuanghai(Yellow)Sea(HS)andEastChinaSea(ECS)hasbeenmadeandreviewedbyscientists,suchasSu(1998),Suetal.(1994),Guan(1985),YuanandSu(1983,2000),Yuanetal.(1997,1988,1994,2001),Tangetal.(2000)andsoon.Inthispapertheseworks willnotbereviewedagainduetolimitationofpages.Thejointinvestigationontheair-seainteractionprocessofcycloneoutbreakoverthesouthernHuanghaiSeaandEastChinaSeawascarriedoutinthecooperativestudybytheChinese(in-clusiveofTaiwa…     

海浪混合参数化的渤海、黄海、东海水动力环境数值模拟

在浪-流耦合的概念下,对Princeton Ocean Model(POM)模式进行改进,增加特征波参数下的海浪混合作用,并把潮流和环流同时模拟,得到了渤海、黄海、东海典型的环流和水文特征,特别是夏季黄海的温跃层现象,夏季长江冲淡水扩展路径以及我国东部海域冬季和夏季典型环流等.研究表明,海浪的作用使海洋上层混合得更均匀,潮流的作用使海洋底层混合得更均匀,二者是温跃层形成的重要原因;考虑潮效应模拟流场,由于潮扩散和潮余流的作用,长江冲淡水路径与实际观测更为符合.     

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.     

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.     

Distribution of zooplankton biomass in the southeastern East China Sea

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东海海水中的溶存甲烷

基于1994年秋季航次在东海的调查资料,较详细地分析了溶存甲烷在水体中的分布规律、成因和来源.表层水中溶存甲烷呈过饱和状态,饱和度127%～254%,温跃层以上水体中,甲烷的断面分布不同于营养盐的分布,各站测值相近,没有显示出受长江冲淡水的影响,而呈现的舌状分布,在陆架底层水中有明显的高浓度甲烷水体,表明甲烷从沉积物中迅速扩散进入底层水.黑潮次表层水的涌升过程稀释了陆架边缘底层水中的甲烷.在陆架和大洋区测站上,甲烷的垂直分布不同,前者主要受物理混合过程所控制;后者呈大洋区分布特征,在温跃层附近出现甲烷的次表层最大,这可能是陆架底层高浓度甲烷沿等密度面的输送所致.     

THE VERTICAL CHARACTERISTICS OF INTERNAL WAVES IN SHALLOW REGION OF THE EAST CHINA SEA ANALYSED FROM CTD DATA

The vertical characters of temperature, salinity and density fluctuations in shallow region of the East China Sea are analysed by using 12 CTD short records with 1-hour intervals. The average S,t and p profiles can be divided into three distinctive layers: the thermocline, and the layers above and below it. The fluctuations of t, S and p are basically caused by internal waves, but there are somewhat intrusions or entrainments at the thermocline boundaries. The vertical displacement of the thermocline centre is up to more than 6.35m and the thermocline thickness changes from 3.5 to 8.0 m. Their varature with time are intermittent and rather irregular. The vertical wavenumber spectra of temperature fluctuations have been estimated by using the maximum entropy method, indicating that energy is mainly contained in the low-wavenumber range (<0.13cpm) with two sharp peaks probably corresponding to the first and second modes of internal waves, whose dependence is estimated to be less than β-2. There exist dep     

南黄海溶解氧的垂直分布特性

根据中韩黄海水循环动力学合作研究项目1996～1998年对南黄海全海域6个航次的现场调查资料,对南黄海溶解氧的断面分布和垂直分布特征及其季节变化规律进行了系统、全面地研究,并对更半年溶解氧垂直分布最大值的地理分布、强度及与温跃层和生物活动的关系等进行了进一步的探讨.     

Numerical study of the influence of Kuroshio Current on the thermocline in the sea area around Taiwan Island

1 INTsoDUcrIONTemperature is one of the most impoFtant essential factors of ocean, and its verticalstructure, especially the phenomenon ofthermocline, is concerned by military and manufacturepractices at all times. There are two classes of research methods for thermocIine, statisticmethod and numerical method. In recent years, more attention has been paid to the latterwhich becomes the primary development direction. Since Munk et al (1948) pot forward1-D model of thermocline at steady sta…     

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     

Baroclinic eddies south of Cheju Island in the East China Sea

The detailed structures of baroclinic eddies, that is, an anticlockwise circulation in the upper layer and a clockwise one in the lower layer south of Cheju Island in the East China Sea have been revealed by intensive field observation. Such baroclinic eddies are accompanied by the southward spreading of the Yellow Sea Bottom Cold Water.     

1998年夏季南海水团分析

根据 1 998年夏季“南海季风试验 ( SCSMEX)”期间所获的 CTD资料 ,使用系统聚类、Fuzzy模式聚类、Bayes判别分析和 Fuzzy分析等水团分析方法 ,对南海水体的结构和水团配置状况等进行了分析 ,划出了南海存在的 9个主要水团 ,并对各水团的温、盐度特征进行了初析。在调查期间 ,南海本地水 (南海水 )几乎控制了整个调查海区 ,而黑潮水仅出现在台湾岛的西南海域 ;海水强烈混合发生在吕宋海峡附近 ;在中南半岛以东和吕宋岛以西海域 ,表层水明显下沉 ;在南海东南部可能有来自苏禄海的海水 ,其温、盐度特征类似于吕宋海峡中的黑潮水     

Features of the hydrological structure and circulation in the north-western Black Sea: shipboard and satellite observations in 1989–1990

The results of shipboard and satellite observations of the synoptic variability in the region of the continental slope south of the Tarkhankut Cape are considered. Ship observations revealed a two-layer circulation system of currents. An anticyclonic meander is localized within the upper mixed layer. A cyclonic disturbance, related to the main Black Sea current, occupies the water column below the seasonal thermocline. The interaction between the thermohaline fields is presumably induced by the anticyclonic atmospheric circulation. The satellite-derived images revealed a complex pattern of the large-scale dynamics of seawater over the entire north-western Black Sea.Translated by Mikhail M. Trufanov.     

南黄海西部2007年4月的逆温跃层

利用南黄海西部2007-04的温盐实测资料,采用海洋层结谱表达法及自适应识别,得到逆温跃层的"五点三要素",形成强度要素平面分布图.分析表明,逆温跃层的存在与黄海暖流水有直接的关系:1)4月份,黄海暖流水受到的海面冷却仍是产生逆温跃层的普遍原因,在该海区黄海暖流向北延伸和向两侧拓展的区域都有该种类型的逆温跃层存在,位置相对较浅;2)但在偏南的黄海暖流主干区,海面冷却产生的效应被主流区的热量补充所抵消,逆温跃层很弱甚至消失,这是该月份逆温跃层分布区向北退缩并在南部中心附近呈现缺失区的主要原因;3)南下的鲁北沿岸流水的冷水叠加在黄海暖流水的暖水上方,使逆温跃层加强,使得冷暖水的作用区成为强逆温跃层区;4)黄海暖流左侧冷沿岸流水及右侧冷水的前端向黄海暖流楔入,其前端往往覆盖在底层高温高盐的黄海暖流水上方形成下逆温跃层,从而形成双逆温跃层.这些特点,较以前认知更加客观、全面、细致和准确.     

黄、东海地理环境与环流系统分析——长江口及济州岛邻近海域综合调查研究报告(第二章)

简要介绍了黄海和东海的地理环境概况,着重分析调查海域的环流系统。有如下一些初步看法与结论。 台湾暖流的前缘混合水,可从长江冲淡水底层穿越而影响到苏北沿岸,直到32°N以北的浅水区域。对马暖流西侧的水体是东海混合水,而其东侧为黑潮分支。黄海暖流的流向在不同季节具有规律的摆动。黄海底层冷水团属于季节性水团,其强盛及消衰与温跃层的形成及消亡紧密相关。黄海底层冷水团与中部底层冷水并非每年彼此独立,它们的共同特征甚至比其差异更明显。夏季东海冷水不能借助爬升侵入黄海底层冷水团内部。在济州岛南部区域,中层的逆温、逆盐现象,是由黄海密度环流的扩散效应与东海冷水沿黄海底层冷水团边界的爬升这两个原因而形成的。