南海等密度面环流季节变化的数值模拟研究

In this study, we develop a variable-grid global ocean general circulation model(OGCM) with a fine grid(1/6)°covering the area from 20°S–50°N and from 99°–150°E, and use the model to investigate the isopycnal surface circulation in the South China Sea(SCS). The simulated results show four layer structures in vertical: the surface and subsurface circulation of the SCS are characterized by the monsoon driven circulation, with basin-scaled cyclonic gyre in winter and anti-cyclonic gyre in summer. The intermediate layer circulation is opposite to the upper layer, showing anti-cyclonic gyre in winter but cyclonic gyre in summer. The circulation in the deep layer is much weaker in spring and summer, with the maximum velocity speed below 0.6 cm/s. In fall and winter, the SCS deep layer circulation shows strong east boundary current along the west coast of Philippine with the velocity speed at 1.5 m/s, which flows southward in fall and northward in winter. The results have also revealed a fourlayer vertical structure of water exchange through the Luzon Strait. The dynamics of the intermediate and deep circulation are attributed to the monsoon driving and the Luzon Strait transport forcing.     

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     

南海环流动力机制研究综述

南海的环流复杂,但通过近20 a来的研究工作,国内外学者对此已取得了不少的成果.本文就南海环流框架性的问题,综述了有关的文献,认为对南海上层海洋三方面的环流分量的驱动机制已有了初步的认识.这三方面分别是:(1)准季节性风场;(2)黑潮向南海的净输运;(3)黑潮向南海的涡度平流输送.但是对这些驱动的时空变化仍相当不清楚.三者皆增强了南海北部的海盆尺度气旋式环流,其强化的西南向西边界流靠近东沙群岛,建议称为“东沙海流”.没有水文证据显示黑潮水是以分支形式进入南海,其向南海的输运也不可能主要通过中尺度涡过程,具体机制有待研究.每年在南海生成的中尺度涡平均约有10个,风场与沿岸地形所生成的强风应力旋度可能是其主要的驱动机制.作为框架性的认识,也有三方面的工作进行得较少,即:(1)吕宋海峡的上层水交换;(2)南海的中尺度涡生成机制,虽然强风应力旋度及前述的第三种环流驱动机制也有中尺度涡伴生;(3)自吕宋海峡进入的深层水对南海上层海洋环流的影响.     

南海表层流场的卫星跟踪浮标观测结果分析

运用卫星跟踪漂移浮标资料分析南海表层海流 ,研究了有关海域的表层海流特征。结果表明 ,秋、冬季入侵南海的黑潮水有一小部分沿台湾南岸折回黑潮主干 ,并有时在台湾西南外海形成反气旋涡旋 ,其余大部分黑潮水西行进入南海内部。吕宋岛西部沿岸流始于 1 3°N以南 ,沿菲律宾西海岸北上抵达吕宋岛西北角 ,与黑潮水混合后西行     

2001年冬春转换期间南海东北部水文和环流特征

根据2001年3月份南海东北部航次调查温、盐资料,分析了2001年冬末春初南海东北部温、盐结构和环流的特征.分析结果表明:观测期间南海东北部环流主要受一次海盆尺度气旋型冷环流支配,冷环流呈现双核结构,垂向尺度接近1000 m.吕宋海峡内侧断面的水交换在600 m以浅海水流入南海,在断面南部(20°N以南)中层和深层有流出,断面法向地转流向西净输运量为6.9×106m3/s;直接的黑潮入侵不超过120.5°E,但有部分的黑潮水沿陆坡达到台湾岛西南部海域,并更有一部分逸入东沙岛以西海域,与南海水混合变性.     

Observations of near surface current at the Luzon Strait in winter

One hundred and ninety-one Argos satellite-tracked drifters deployed at the Luzon Strait in winter during 1991 to 2004 were ana- lyzed to understand the near surface current in northern South China Sea (SCS). Several major track patterns of these drifters have been found. There are: (1)shelf slope landing way (SLW) ; (2)deep basin way (DBW) ;(3) weak loop current pattern; (4) northward movement directly driven by the Kuroshio. These observations show the effects of the basin scale gyre circulation, mesoscale eddies and the Kuroshio on the drifters' ovement.     

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。     

Interannual variability of the Kuroshio intrusion in the South China Sea

The interannual variability of intrusions of the Kuroshio into the South China Sea (SCS) is investigated using satellite remote sensing data supported by in-situ measurements. The mesoscale circulation of the SCS is predominantly wind-forced by the northeast winter and southwest summer monsoons. Although the region has been studied extensively, considerable uncertainty remains about the annual and interannual mesoscale nature of the circulation. The frequency and characteristics of Kuroshio intrusions and their effect on circulation patterns in the northeast SCS are also not well understood. Satellite observations of Sea Surface Temperature (SST) from the Tropical Rainfall Measuring Mission (TRMM) and the Advanced Very High Resolution Radiometer (AVHRR) and Sea Surface Height Anomalies (SSHA) from TOPEX/ Poseidon for the period 1997–2005 are used here to analyze the annual and interannual variability in Kuroshio intrusions and their effects on the region. Analysis of SST and SSHA shows the formation and characteristics of intrusions vary considerably each year. Typically, the intrusion occurs in the central region of Luzon Strait and results in an anticyclonic circulation in the northeastern SCS. However, in some years, the intrusion is located in the northern portion of Luzon Strait and a cyclonic intrusion results. Wind stress and wind stress curl derived from the National Aeronautics and Space Administration (NASA) QuikSCAT satellite scatterometer are used to evaluate the relationship between wind stress or wind stress curl and the presence of winter Kuroshio intrusions into the SCS.     

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.     

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.     

Sea surface height anomaly and geostrophic circulation variations in the South China Sea from TOPEX/POSEIDON altimetry

The sea surface height anomaly (SSHA) and geostrophic circulation in the South ChinaSea (SCS) are studied using TOPEX/POSE1DON (T/P) altimetry data. The SSHA, which is obtained after tidal correction based on the tidal results from T/P data, is predominated by seasonal alternating monsoons. The results reveal that the SSHA in the central part of the SCS is positive in spring and summer, but negative in autumn and winter. It is also found that the SSHA in the SCS can be approached with the sum of tidal constituents SA and SSA. The geostrophic circulations in the SCS are calculated according to sea surface dynamic topography, which is the sum of SSHA and mean sea surface height. It is suggested that the circulation in the upper layer of the SCS is generally cyclonic and notably western intensified during autumn and winter, while the western intensification is weak during spring and summer. It is also indicated that the Kuroshio intrudes into the northeastern SCS throuth the Luzon Strait in winter. But ther     

吕宋海峡两侧中尺度涡统计

利用1993-2000年间的T/P卫星高度计轨道资料的时间序列和MODAS同化产品中的卫星高度计最优插值资料对南海东北部海区中尺度涡旋进行动态追踪。按照给定的标准从2种资料中提取了涡旋信息并对其特征量进行统计分析。结果表明,南海东北部海区中尺度涡旋十分活跃,平均每年6个,其中暖涡4个,尺度一般为200~250 km,平均地转流速为44 cm/s;冷涡每年平均2个,尺度一般为150~200 km,平均地转流速为-37 cm/s。吕宋海峡两侧涡旋的比较分析表明,南海东北部海区仍属于西北太平洋副热带海区的涡旋带,冷、暖涡旋处于不断的形成—西移—消散过程中。南海东北部中尺度冷涡大多是南海内部产生的,而暖涡与吕宋海峡外侧暖涡有一定的联系又具有相对的独立性。分析认为西北太平洋的西行暖涡在到达吕宋海峡时,受到黑潮东翼东向下倾的等密度面的抑制和岛链的阻碍,涡旋停滞于吕宋海峡外侧并逐渐消弱,被阻挡于吕宋海峡东侧涡旋释放的能量,形成一支横穿吕宋海峡(同时横穿过黑潮)的高速急流,把能量传递给吕宋海峡西侧的涡旋,使其得到强化,这是吕宋海峡两侧涡旋联系的一种重要机制。     

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.     

Numerical study on the summer circulation of the upper South China Sea and its establishment

A coupled single-layer/two-layer model is employed to study the South China Sea (SCS) upper circulation and its response before and after the onset of summer monsoon. It is found that, in summer, due to the β effect and the first baroclinic mode of the wind-driven current, a northward western boundary jet current is formed along the Indo-China Peninsula coast, and it leaves the coast at about 13° N and diffuses towards northeast; next to the Indo-China Peninsula, a large anticyclonic     

冬季南海上层环流动力机制的数值研究

通过利用一个分区性的正压-斜压衔接模式来探讨冬季南海的上层环流特征及其动力机制,结果表明:(1)在南海北部,流态主要受黑潮的影响,除了东沙群岛西南的大陆架海域以及吕宋岛北部西岸附近各为一反气旋涡外,整个南海北部为一气旋式大环流所控制.(2)在南海南部主要是风生环流,源自粤西沿岸的水体在东北季风的作用下顺南海西边界岸线向南流动,形成一支相当强的西边界流;同时,由于受北康暗沙以南的陆架坡底形效应和β效应的作用,使得在南海南部出现以一个反气旋涡在南沙海槽处产生、发展并向西传播乃至衰减的约50d的周期性过程     

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。     

Several significant hydrographic characteristics and their formation mechanism in the South China Sea during the spring and summer of 1998

INTRODUCTIONTheSCSisthelargestmarginseainthewestoftheNorthPacificOcean .Theprevailingwindinwinterisnortheast,whileinsummeritissouthwest .Itisstilluncertainthathowthecirculationandtemperature -salinityfieldassociatewiththemonsoonforcingandaccompanywithseveralkindsofvariationsbeforeorafterthesummermonsoonburst .DuringSECMEXin 1 998,twointensiveobservationperiods (IOP)havebeencarriedoutntheSCS (Fig 1 ) :IOP1 ,from 1 0Aprilto 5May ;IOP2 ,from 1 2JunetoJuly 6 ,inordertounderstandthe…     

Surface current field and seasonal variability in the Kuroshio and adjacent regions derived from satellite-tracked drifter data

The muhiyear averaged surface current field and seasonal variability in the Kuroshio and adjacent regions are studied. The data used are trajectories and （1/4） ° latitude by （1/4） ° longitude mean currents derived from 323 Argos drifters deployed by Chinese institutions and world ocean circulation experiment from 1979 to 2003. The results show that the Kuroshio surface path adapts well to the western boundary topography and exhibits six great turnings. The branching occurs frequently near anticyclonic turnings rather than near cyclonic ones. In the Luzon Strait, the surface water intrusion into the South China Sea occurs only in fall and winter. The Kuroshio surface path east of Taiwan, China appears nearly as straight lines in summer, fall, and winter, when anticyclonic eddies coexist on its right side; while the path may cyclonically turning in spring when no eddy exists. The Kuroshio intrusion northeast of Taiwan often occurs in fall and winter, but not in summer. The running direction, width and velocity of the middle segment of the Kuroshio surface currents in the East China Sea vary seasonally. The northward intrusion of the Kuroshio surface water southwest of Kyushu occurs in spring and fall, but not in summer. The northmost position of the Kuroshio surface path southwest of Kyushu occurs in fall, but never goes beyond 31 °N. The northward surface current east of the Ryukyu Islands exists only along Okinawa-Amami Islands from spring to fall. In particular, it appears as an arm of an anti- cyclonic eddy in fall.     

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.     

南海东北部海域次表层水与中层水之流径

1992年春季以及1994年夏季，台湾海峡两岸曾同时出动多艘研究船在南海东北部海域协力执行了两次较大区域的水文调查作业。根据温盐曲线之类聚情形，发现盐温变率比（即温盐曲线斜率之倒数）是除了盐度极大值与盐度极小值外另一个简单又好用的温盐特征参数。此值乍视之下仅与温盐曲线之形状有关，但因其隐涵了时间的效应，故可有效反映出水团之变性程度，对分析、推断水团之流径甚有助益。经分析、对比温盐参数与动力高度之水平分布，发现1992年春季观测时之地转流场与温盐参数二者趋势不甚一致，但1994年夏季之测情却有很好的共通性，似乎表示后者之流况系处于稳定状态，因此观测现象应较具代表性。资料亦显示：不论春、夏，在吕宋岛西北角与东沙群岛之间的广大海域主要是受成群的气旋型环流所控制，此气旋群之范围因季节而异，夏季时其势力较向东、向北扩展，因而在巴士海峡、巴林塘海峡阻挡住黑潮区之外洋次表层与中层水团向西伸展，但外洋水团仍可在台湾岛南端逸入南海东北部，然后被南海内部流系辗转带往南海腹地。春季时，外洋水团虽可占据气旋群环流场东北方之台湾西南外海，但并未见能长驱直入南海内部者，仅有部分经变性后之外洋水被气旋群西侧之环流带往南海中部，表示逸入过程是南海与西菲律