南海西北陆坡区内潮与近惯性内波观测研究

通过对2006年南海西北部海域近3个月的全水深流速观测资料的分析,研究了该海区正压潮、内潮及近惯性内波的时空分布特征。结果表明,全日内潮明显强于半日内潮,且最大潮流均出现在海洋上层;内潮的主轴方向基本沿东南-西北方向,近似与局地等深线垂直;内潮能量显示出明显的时间长度约为半月的大小潮调制周期;全日内潮的coherent部分占全日内潮能量的70%,而半日内潮的coherent部分占半日内潮能量的53%;进一步研究发现半日内潮主要由第一模态主导,而全日内潮第三模态能量占总能量的比例仅次于第一模态且量值上与之相当;强风过程可激发出强的近惯性运动,暖涡使得近惯性内波能量更有效地向海洋深层传播,冷涡则不利于近惯性内波能量向下传播。     

A study of internal solitary waves observed on the continental shelf in the northwestern South China Sea

Based on in-situ time series data from the acoustic Doppler current profiler (ADCP) and thermistor chain in Wenchang area, a sequence of internal solitary wave (ISW) packets was observed in September 2005, propagating northwest on the continental shelf of the northwestern South China Sea (SCS). Corresponding to different stratification of the water column and tidal condition, both elevation and depression ISWs were observed at the same mooring location with amplitude of 35 m and 25 m respectively in different days. Regular arrival of the remarkable ISW packets at approximately the diurnal tidal period and the dominance of diurnal internal waves in the study area, strongly suggest that the main energy source of the waves is the diurnal tide. Notice that the wave packets were all riding on the troughs and shoulders of the internal tides, they were probably generated locally from the shelf break by the evolution of the internal tides due to nonlinear and dispersive effects.     

南海北部相干内潮和非相干内潮演变特征

通过南海北部跨越陆坡和陆架区的3套潜标数据,对全日和半日相干、非相干内潮的动能变化特征进行了研究。研究表明,全日内潮沿陆坡区向陆架区传播的过程中,在陆坡区主要以全日相干内潮生成为主,平均动能生成率为2.32 J/（m3·s）;在陆架区以全日相干内潮耗散为主,平均动能耗散率为0.44 J/（m3·s）。全日非相干内潮动能在陆坡和陆架区均增长,平均动能生成率分别为0.39 J/（m3·s）和0.03 J/（m3·s）。全日与半日相干内潮动能在陆坡和陆架区的表现不同,陆坡区的全日相干内潮动能明显大于陆架区的全日相干内潮动能,而半日相干内潮动能在陆坡和陆架区没有明显差别;陆架区的全日和半日非相干内潮动能要大于陆坡区的全日和半日非相干内潮动能。     

南海东北部内潮的模态结构和传播

The evolution of energy, energy flux and modal structure of the internal tides(ITs) in the northeastern South China Sea is examined using the measurements at two moorings along a cross-slope section from the deep continental slope to the shallow continental shelf. The energy of both diurnal and semidiurnal ITs clearly shows a～14-day spring-neap cycle, but their phases lag that of barotropic tides, indicating that ITs are not generated on the continental slope. Observations of internal tidal energy flux suggest that they may be generated at the Luzon Strait and propagate west-northwest to the continental slope in the northwestern SCS. Because the continental slope is critical-supercritical with respect to diurnal ITs, about 4.6 kJ/m~2 of the incident energy and 8.7 kW/m of energy flux of diurnal ITs are reduced from the continental slope to the continental shelf. In contrast, the semidiurnal internal tides enter the shelf because of the sub-critical topography with respect to semidiurnal ITs.From the continental slope to the shelf, the vertical structure of diurnal ITs shows significant variation, with dominant Mode 1 on the deep slope and dominant higher modes on the shelf. On the contrary, the vertical structure of the semidiurnal ITs is stable, with dominant Mode 1.     

南海北部陆架区内孤立波向岸传播过程研究

南海北部是全球海洋中内孤立波最强和最为活跃的海域。然而,内孤立波在传入陆架区后,其形态发生显著变化,其传播演变过程表现出高度的复杂性。本研究综合卫星图像和数值模式手段研究了内孤立波在向岸传播过程中的空间变化特征。可见光卫星图像研究结果显示,南海北部陆架区存在三种形态的内孤立波,分别为第一模态下凹型内孤立波、第一模态上凸型内孤立波和第二模态内孤立波。受水深和层结变化的控制,它们的分布区域显著不同。基于MITgcm的数值模拟研究表明,上凸型内孤立波由第一模态下凹内孤立波经过极性转换过程发展而来,而第二模态内孤立波由第一模态下凹内孤立波与急剧变浅地形相互作用而产生。     

Simulation of barotropic and baroclinic tides in the South China Sea

The four leading tidal constituents M2, S2, K1 and O1 in the South China Sea are simulated by using POM. The model is forced with tide-generating potential and four leading tidal constituents at the open boundary. In order to simulate more exactly, TOPEX/Poseidon altimeter data are assimilated into the model and the open boundary is optimized. The computed co-tidal charts for M2 and K1 constituents are generally consistent with previous results in this region. The numerical simulation shows that energetic internal tides are generated over the bottom topography such as the Dongsha Islands, the Xisha Islands, the Zhongsha Islands, the Nansha Islands and the Luzon Strait.     

1998年南海北部20天定点连续观测的内潮分析（英文）

对1998年6月南海北部20天的海流和温度定点连续观测资料进行分析,得到该海域内潮的特征及其能量分布。分析结果显示内潮的主要成分为O1,K1,M2与S2分量,其中全日内潮（O1与K1）的能量占主要部分。在观测期间,此四个分量的海流失量均为顺时针旋转,其潮流椭圆半长轴的最大值超过14cm/s。海水温度的变化显示出内潮存在准日周期振动,平均垂向振幅达到50m。观测到的内潮携带高能量且其活动存在不连续性,在观测范围内,全日内潮的动能及势能密度的最大值分别达到2kJ/m^2及3.5kJ/m^2,半日内潮的动能及势能密度的最大值分别达到1kJ/m^2及1.5kJ/m^2。     

Turning depths of internal tides in the South China Sea inferred from profile data

Theoretically, propagating internal tides in the ocean may reflect at turning depths, where buoyancy frequencies equal tidal frequencies, before colliding with the air-sea interface or rugged bottom topography. Globally, the internal tide lower turning depths（ITLTDs） in the open ocean have been mapped; however, knowledge of the presence of ITLTDs in the South China Sea（SCS） is lacking. In this study, 2 125 high-quality temperature-salinity profiles（including 58 deep-sea hydrographic measurements...     

南海北部中尺度涡与内波相遇的特征分析

基于2009年12月~2010年4月南海北部大陆坡上东沙岛以西的一套潜标资料,分析一个中尺度涡与内波相遇时海水温度的变化特征。根据潜标上的温压记录,利用功率谱分析,发现潜标布放处存在周期为20~30 min的内孤立波及全日和半日周期的内潮;结合海表面高度异常资料,描述此处一个中尺度涡的经过过程。利用天文潮大潮发生的时间规律,推断出中尺度涡与内波的相遇,从而解释了压力记录的异常变化。根据中尺度涡与内波各自引起的海流流向,分析在本次观测中两者相遇时的共同作用所引起的海水温度的垂向变化,即当两者引起的流向相反时,内波引起的日周期等温线波动由上凸型弧状变为下凹型弧状,短时震荡由向下振荡变化为向上振荡。     

2007年春季南海西北部陆架区海域浮游植物的群落结构

据2007年春季在南海西北部陆架区海域进行的网采浮游植物调查数据,分析了浮游植物群落的结构特征．此次共鉴定出浮游植物4门318种,其中硅藻类183种,甲藻类128种,蓝藻类5种,金藻类2种．大部分海域浮游植物种类数在40～70种之间,外海区域的种类数稍高于沿岸．浮游植物密度的变化范围为0．22×10。～3683．85×10。eells／m’,平均值（标准偏差）为97．49×10。（±437．38×10。）cel｜s／m。．其高值区主要位于粤西近岸海域,向外海呈递减趋势．调查海域硅藻类的平均密度（标准偏差）最高,为93．82×10。（±434．34×10。）cells／m’;甲藻类的次之,为3．65×10。（±9．08×10。）cells／m’．浮游植物优势种主要有拟旋链角毛藻（Chaetocerospseudocurvisetus）、细弱海链藻（Thalassiosirasubtilis）、中肋骨条藻（Skeletonemacostatum）、劳氏角毛藻（Chaetocerosloren—zianus）和菱形海线藻（Thalassionemanitzschioides）．该调查海域浮游植物多样性指数的变化范围为1．48～6．23,平均值（标准偏差）为4．70（±1．03）,其分布趋势与浮游植物密度的分布趋势大致相反．将站位依等深线划分为粤西近岸海区、琼东南近岸海区和外海海区,应用非度量多维标度（nMDS）和聚类分析法分析这3个海区的浮游植物群落结构差异,并通过ANOSIM和SIMPER进行检验．结果表明3个海区之间浮游植物群落结构具有显著性差异,且粤西近岸海区与外海海区之间差异性较高．近岸种拟旋链角毛藻和中肋骨条藻在粤西近岸海区为最主要的优势种,而外海海区优势种较多,且大部分为大洋暖水性种类．     

Mooring observed mode-2 internal solitary waves in the northern South China Sea

The mode-2 internal solitary waves (ISWs) generated by mode-2 internal tide (IT) are identified by mooring observations in the northern South China Sea (SCS) from 2016 to 2017. Two mode-2 ISWs with a re-appearance period of 24.9 h observed on 29 and 30 July 2016 are characterized by type-b ISWs. They occurred when the isotherms compressed obviously in the vertical direction. Modal decomposition of IT horizontal currents shows that the vertical compression of the isotherms is mainly caused by diurnal mode-2 IT. The analysis of the role of the density stratification reveals that a deeper and thinner pycnocline is favorable for generation of mode-2 ISWs rather than pycnocline intensity. By comparing the mode-2 nonlinear, dispersion coefficients and the Ursell numbers calculated based on the stratification associated with different kinds of ITs with the observation results, it is shown that the diurnal mode-2 IT plays a crucial role in the generation of the mode-2 ISWs. When the diurnal mode-2 IT interacts with the semidiurnal IT and causes a deeper and thinner pycnocline, the mode-2 ISWs are easily excited.     

Observing spectral characteristics over a continental shelf and slope in the South China Sea

Using in situ measurement data from May-June, 1998, and data from the Asian seas international acoustics experiment （ASIAEX） from 2001 in the South China Sea （SCS）, the spectral density function and the dissipa- tion spectrum function are estimated. In the inffa-gravity wave （IGW） band, the power spectra of velocity （u, v, w） are universal functions with respect to characteristic frequencies, which correspond to the peak fre- quencies of the dissipation spectrum （PFDS）. This suggests that high-frequency internal waves in the IGW band have similar dynamical characteristics. In addition, the evolution of these characteristic frequencies is explored and its highest value is 8.8 cph （cycles per hour, 1 cph=2.778× 10-3 Hz）.     

南海北部孤立波对近岸波动的响应

On the basis of the time series observations from a temperature chain and an acoustic Doppler current profiler on the continental shelf of the northern South China Sea, a sequence of internal solitary waves （ISWs） and background waves （BWs, including internal tides and near-inertial waves） on the continental shelf were captured simultaneously after the transit of Typhoon Neast in October 2011. These measurementsprovided a unique opportunity to explore the influence of BWs on the ISWs. The BWs appeared a conversion on the current strength and vertical mode structure during the observational period. The BWs were dominated by weak and mode-one waves before October 2 and then turned to strong and high-mode waves after that time. Meanwhile, the ISWs displayed different wave structures before and after October 2, which was closely related to BWs＇ changes. According to the current profiles of BWs, the high-mode wave structure with strong current could significantly strengthen the vertical shear of ISWs in the near-surface layer and promote the breaking of ISWs, and thus it may play an important role in affecting the background current condition.     

基于X波段海洋雷达的南海西北部内波参数特征研究

中国南海是内波频发海域,卫星遥感在内波参数特征的统计分析中得到了广泛应用,但是卫星轨道的重复访问时间长,不能连续观测内波参数的变化特征。X波段海洋雷达具有高时间和空间分辨率,可以长期连续观测内波的变化,本文提出了利用X波段海洋雷达图像提取内波参数的方法,并利用连续观测的数据研究了各参数的分布特征。首先,对雷达图像进行预处理,包括平均处理及斜坡校正两步;利用二维快速傅里叶变换确定内波的传播方向,进而根据该方向上的径向廓线确定内波的相速度大小、波长及周期。最后,利用在南海石油平台上观测的X波段雷达图像对内波各参数进行提取和统计分析,结果表明,研究区域内波的传播方向多为西北向及西向传播,相速度多为0.6～0.8 m/s,波长一般为400～600 m,周期大部分不超过1000 s。     

Estimates of mixing on the South China Sea shelf

1 Introduction The outer shelf of the South China Sea is a di- verse environment characterized by sharp changes in bottom topography (Wang et al., 2002). Internal wave and diapycnal mixing may be a vital mechanism con- trolling the distribution of physical water properties, nutrient fluxes, and concentrations of particulate mat- ter. Therefore, the research on diapycnal mixing on the outer shelf in the South China Sea is of great impor- tance to explore the level and variability of the abov…     

南海北部陆架区底层渔业资源的空间分布特征

根据2006年10月至2007年9月南海北部大陆架海域4个航次底拖网调查资料,分析了该海域渔业资源的种类组成、种类丰富度和渔获率的空间分布。结果表明,渔获种类数以湛江断面最多(405种),汕头断面最少(337种)。种类数随水深变化呈非对称正态分布,以40—80m水深组种类数最多。物种丰富度指数D的空间分布与种类数基本一致。在总渔获物中,鱼类、头足类和甲壳类3大类群重量组成比例为80:12:8,在断面分布上,组成比例鱼类以珠江口断面最高,头足类以湛江断面最高,甲壳类以阳江断面最高。在水深分布上,鱼类占比随水深的增加而增加,头足类占比在40—100m水深较高,甲壳类在10—20m浅水区最高。鱼类最主要的优势种有6种,其中,深水金线鱼主要在90—120m水深占优势,黄鳍马面鲀在60—90m水深占优势,条尾绯鲤在60—120m水深占优势,单棘豹鲂鮄在120—200m水深占优势,六指马鲅在30—60m水深占优势,龙头鱼在10—30m水深占优势。鱼类渔获率断面分布以珠江口和粤西海域较高,汕头海域最低;水深分布渔获率随水深的增加而增加。头足类渔获率以粤西和珠江口海域较高,粤东海域较低;在100m水深范围内,渔获率随水深的增...     

Assessing the west ridge of Luzon Strait as an internal wave mediator

The Luzon Strait is blocked by two meridional ridges at depths, with the east ridge somewhat higher than the west ridge in the middle reaches of the Strait. Previous numerical models identified the Luzon Strait as the primary generation site of internal M₂ tides entering the northern South China Sea (Niwa and Hibiya, 2004), but the role of the west-versus-east ridge was uncertain. We used a hydrostatic model for the northern South China Sea and a nonhydrostatic, process-oriented model to evaluate how the west ridge of Luzon Strait modifies westward propagation of internal tides, internal bores and internal solitary waves. The dynamic role of the west ridge depends strongly on the characteristics of internal waves and is spatially inhomogeneous. For M₂ tides, both models identify the west ridge in the middle reaches of Luzon Strait as a dampener of incoming internal waves from the east ridge. In the northern Luzon Strait, the west ridge is quite imposing in height and becomes a secondary generation site for M₂ internal tides. If the incoming wave is an internal tide, previous models suggested that wave attenuation depends crucially on how supercritical the west ridge slope is. If the incoming wave is an internal bore or internal solitary wave, our investigation suggests a loss of sensitivity to the supercritical slope for internal tides, leaving ridge height as the dominant factor regulating the wave attenuation. Mechanisms responsible for the ridge-induced attenuation are discussed.     

南海西北部陆架区住筒虫属的种类描述及其丰度分布

住筒虫是浮游被囊动物的一类,隶属于脊索动物门、尾索动物亚门、有尾纲、住筒虫科、住筒虫属,在海洋生物食物链中占重要位置。根据南海西北部陆架区2006年夏季、冬季和2007年春季3个航次各82个站的浮游动物拖网(网目孔径169 μm)调查资料,共鉴定到8种住筒虫:Fritillaria aberrens,F.abjornseni, F.formica, F.haplostoma, F.megachile, F.pacifica, F.pellucida, F.tenella,其中F.aberrens、F.abjornseni和F.pacifica为南海新纪录。对它们进行了形态描述,并结合环境因子探讨其丰度分布特征。夏季出现住筒虫8种,平均丰度为(2.62±4.68 )个/m3;冬季3种,春季4种,平均丰度分别为(0.23±0.52)和(1.72±5.43)个/m3。F.formica是丰度最高的一种,在夏季、冬季和春季分别占总丰度的43.88%,80.18%和84.29%;其次是F.pellucida和F.haplostoma;以上三种分布广,丰度较高。与环境因子分析表明,夏季琼东沿岸上升流和雷州半岛东部海域冷涡现象对种类向沿岸推移及其丰度增加有一定的助长作用。     

南海东沙岛西南大陆坡内潮特征

2008年4月-10月,在南海东沙岛西南大陆坡底部布放了1套全剖面锚系,同时沿大陆坡底部布放了3套近底锚系,应用谱分析和调和分析方法分析温度和海流连续观测资料,进而研究该海域的内潮特征.结果表明,东沙岛西南大陆坡存在强内潮现象,大陆坡底部温度变化受到内潮波的影响,上层海洋存在强日潮周期的内潮波振动;正压潮和斜压潮均以O...     

2015年春季南海北部陆架海域网采浮游植物群落结构及其与环境因子关系

根据2015年春季南海北部陆架海域的调查数据,分析了网采浮游植物群落结构特征及其与环境因子的关系。结果显示:共鉴定出浮游植物4门378种(含变种与变型),其中硅藻门209种,甲藻门157种,蓝藻门9种,着色鞭毛藻门3种。该海区的主要优势种有翼鼻状藻Proboscia alata、翼鼻状藻纤细变型Proboscia alata f. gracillima、佛氏海毛藻Thalassiothrix frauenfeldii、尖刺拟菱形藻Pseudo-nitzschia pungens、短角弯角藻Eucompia zoodiacus和洛氏角毛藻Chaetoceros lorenzianus等,各断面优势种差异较大,仅佛氏海毛藻在4个断面成为优势种。浮游植物丰度范围为(0.63~1 430.04)×10⁴个/m³,平均为76.20×10⁴个/m³,丰度较高的站点主要集中在湛江断面D近岸站位和汕头断面H。春季南海北部浮游植物Shannon-Wiener多样性指数为1.06~5.56,均值为3.99。冗余分析显示,影响南海北部陆架海域浮游植物群落结构的主要环境因子为水温、盐度和活性磷酸盐。南海北部陆架海域浮游植物基本呈现近岸高离岸低的分布特点,水温和盐度是影响其分布的主要环境因子。