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1.
《中国海洋大学学报(自然科学版)》2021,(11)
高分一号是中国自主发射的光学遥感卫星,空间分辨率达到2、8和16 m,因此可以为尺度较小的第二模态内孤立波研究提供强有力的数据支撑。本文基于2014—2020年共7年高分一号光学遥感图像研究了南海东沙岛北部第二模态内孤立波特性,研究结果表明:在海水层结不变,海域第二模态内孤立波的光学遥感图像条纹亮暗次序与第一模态内孤立波的相反;第二模态内孤立波的波峰线远短于第一模态内孤立波的波峰线;南海东沙岛北部第二模态内孤立波在夏季被光学遥感观测到的概率最大;绝大部分第二模态内孤立波尾随在第一模态内孤立波之后,可能是第一模态内孤立波与地形凸起相互作用而产生了第二模态内孤立波。这一研究结果对于进一步研究全球海域第二模态内孤立波的特性奠定了良好基础。 相似文献
2.
南海北部陆架区内孤立波向岸传播过程研究 总被引：1，自引：0，他引：1
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。 相似文献
3.
现场观测和卫星遥感SAR图片均表明,台湾岛东北海域存在大量复杂的、无规则的内孤立波(列)。本文采用完全非线性非静力平衡的MITgcm模式,分别采用M2和K1分潮驱动,对该海域内孤立波的生成过程及其机制进行了二维数值模拟研究。研究揭示,该海域的内孤立波主要源于附近2个海槛处的潮地相互作用。正压潮流流经海脊时会激发内孤立波,潮流由退潮转换为涨潮时激发西向传播的内孤立波,由涨潮转换为退潮时则激发东向传播的内孤立波。通过对潮汐偏移及地形弗鲁德数的分析表明,内孤立波的产生机制是混合山后波机制。在海槛西侧,内孤立波在涨潮时向西传播,在落潮时受背景潮流的限制,西传速度明显减慢,甚至停滞;在海槛东侧,存在东传的第二模态内孤立波,并最终在向深海传播过程中逐渐消亡。本文设计了6个敏感性试验,以考察不同因子对内孤立波的生成和传播过程的影响。不同分潮驱动的数值实验表明,此区域的内孤立波主要是由半日分潮M2引起的,由于靠近全日分潮的临界纬度,单独的K1分潮不激发内孤立波。其他敏感性实验显示,海水层化对内孤立波的生成和传播有较大影响;科氏力对内孤立波的传播速度有一定的影响。 相似文献
4.
内孤立波对大陆架边缘海区的混合和生态有着显著影响，近年来已成为物理海洋学研究的热点。但是南海北部陆架的内波现场资料极为缺乏。2005年4—7月，中国科学院海洋研究所在文昌海区进行了文昌内波实验。通过此次现场观测数据发现，在4月下旬文昌海域有着强盛的内孤立波，其振幅在40m左右，产生的斜压流接近1m／s，且传播方向平行于等深线切线方向，向西南方向传播。分析还得出此类内孤立波并非发源于吕宋海峡，应该属于潮地相互作用局地生成的内孤立波。 相似文献
5.
veKdv方程的若干系数在南海北部的地理分布特征及其季节变化分析 总被引：1，自引：1，他引：0
应用中国近海及邻近海域海洋再分析资料(简称CORA)研究南海北部第一模态内波场运动学参数的地理分布特征及其季节变化。首先分析了Brunt-Väisälä频率的统计特征;其次,基于弱非线性变系数扩展Kortewed-de Vries (veKdv)方程模型,计算了它的输入系数,即线性长波相速度,平方和立方非线性系数和频散系数,这些参数可用于定性评估内孤立波传播可能的极性,内孤立波的形态,幅度限制以及传播速度等。分析结果表明,南海北部季节性密度跃层从2月开始出现,最大浮力频率约在20 m。它在6—7月达到最强,自8月开始减弱,在10月消退。另一密度跃层出现在8—11月,最大浮力频率约在80 m,冬季大致在120 m。季节性密度跃层在4—9月十分明显,而8—10月双跃层现象显著,冬季仅出现较弱的第二密度跃层。在1—3月和10—12月海盆深水区最大Brunt-Väisälä频率值要大于陆架浅水区;而在5—9月情况则相反。Brunt-Väisälä频率最大值所在深度随季节变化显著,冬季最深,6—7月则最浅。计算的线性内波相速度、频散系数和幅度放大因子的空间特征主要取决于地形变化;平方(立方)非线性系数与地形关系较小,随季节变化明显,它们主要取决于局地海洋环境特征。通过分析veKdv方程的系数特征,解释了为何在夏季南海北部最容易观测到大振幅内孤立波和在吕宋海峡以东海域难以观测到孤立波的原因。 相似文献
6.
基于布放在南海东北部陆坡海域的5套潜标观测到的内孤立波波列数据和孤立波扰动KdV(PKdV)理论,研究内孤立波在趋浅陆架上的传播特征。得出如下结果:1)观测到的内孤立波属于C型内孤立波,即平均重现周期为(23.41±0.31)h。2)内孤立波在西传爬坡过程中,其振幅表现为先增大后减小再增大,与该海域温跃层深度的变化趋势一致;由观测数据和理论计算得到的孤立波振幅增长率(SAGR)数值接近,表明该海域的内孤立波的振幅变化可以采用由孤立波PKdV方程导出的趋浅温跃层理论来描述。3)随着水深变浅,内孤立波传播方向向北偏移,传播速度减小,即在A,B和D站位,传播方向分别为279°,296°和301°,偏转角度达22°;传播速度分别为2.36,2.23和1.47 m/s,减小38%。 相似文献
7.
一个典型南海北部第二模态内孤立波的观测分析 总被引：1，自引：0，他引：1
第二模态内孤立波在海洋中极少被观测到。本文基于潜标高时空分辨率观测数据,对南海北部陆架区的一个典型第二模态内孤立波进行了分析。结果表明,该第二模态内孤立波的流核出现在135 m深度处,其最大水平流速为0.66 m/s,传播方向为西偏北58°。沿传播方向的内孤立波流速分布在80～170 m的深度范围内,而与传播方向相反的逆流出现在海表和海底附近。垂向模态分析表明,该第二模态内孤立波水平流速的垂向结构与理论结果吻合良好。能量计算结果显示其动能密度的垂向积分可达14 kJ/m2,而波峰线方向单位长度上的动能估算值为5.98 MJ/m。尽管该第二模态内孤立波的动能比陆架区第一模态内孤立波小1个量级,但其高达0.045 s-1的流速垂向剪切约为典型第一模态内孤立波的2倍,表明其导致的混合可能更强。 相似文献
8.
内波破碎引起的能量耗散和混合是海洋内部的重要物理过程。通过在二维内波水槽进行实验室实验,分析内波与地形的作用,探究内孤立波与平顶海山地形作用时波要素、能量以及湍耗散率的时空变化。本实验利用重力塌陷法在两层流体中制造第一模态内孤立波,通过粒子图像测速技术(particle image velocimetry, PIV)获得内孤立波与地形作用时的流场结构,定量分析整个作用过程。结果表明,地形会改变波形甚至引起破碎,内波与地形作用时,振幅和能量密度会在内孤立波爬坡时迅速增大,在地形前缘产生强烈能量耗散。入射波的能量与塌陷高度呈二次函数关系,透射波能量随地形升高减小,反射波能量随地形升高增大。地形前缘局地湍耗散率极值时间序列在部分实验中呈双峰结构,对应内孤立波界面处剪切加强引起湍流耗散和波后缘翻转破碎。破碎引起的地形前缘区域平均湍耗散率量级在10~(-5)m~2/s~3,局地湍耗散率极值与入射波振幅呈指数关系,所有实验中局地湍耗散率的最大值接近10~(-3) m~2/s~3量级。 相似文献
9.
海洋内波具有振幅大、流速强和周期短等特点,可对海上施工和水下作业安全造成严重威胁。南海北部陆坡海域是内孤立波和中尺度涡频发的海域之一,研究中尺度涡对内孤立波传播的影响对深入了解南海北部内孤立波在反气旋涡过境时的传播特征、提高该海域内波预报准确性具有重要意义。基于此,本文利用布放于南海北部东沙群岛西侧陆坡海域的潜标观测数据,针对2017年3月一个反气旋中尺度涡经过潜标站位的过程,探讨了中尺度涡对内孤立波传播的影响。结果表明：①受反气旋涡影响,内孤立波的平均振幅减小28.6%,其主要原因是中尺度涡导致等温线下压,进而对内孤立波的振幅产生抑制作用,其影响过程可用趋浅温跃层理论描述。②反气旋涡影响期间,内孤立波的平均波速由1.26 m/s增大到1.47 m/s,增幅约16.7%,反映了反气旋涡对内孤立波波速的强化作用,这种强化作用主要是由中尺度涡边缘流场引起背景流场变化所致,而中尺度涡引起的温盐场变化对内孤立波波速的影响相对较小。 相似文献
10.
活跃在中国南海的内孤立波已经成为该地区海洋油气资源开发中不得不考虑的因素。跨接管作为连接水下油气储存开采设施与海面油气处理设施的重要装置,由于具有较大柔性,由内孤立波引起的剪切海流将会对其产生巨大影响。采用KdV方程对内孤立波进行模拟,基于向量式有限元法,建立了柔性跨接管的动力学分析模型,对不同方向内孤立波作用下的跨接管的动力性能进行分析。分析结果表明在内孤立波作用下,跨接管存在一个明显的动力过程,能够导致跨接管产生较大的位置移动及其整体位置的抬升,同时跨接管对于内孤立波的入射角十分敏感,其内力可能发生突然变化。内孤立波的振幅对跨接管的极值响应有显著影响。 相似文献
11.
南海北部陆坡区内孤立波的垂向热量输送 总被引：1，自引：0，他引：1
An integrated analysis of internal solitary wave(ISW) observations obtained from two moorings over the continental slope in the northern South China Sea(SCS) leads to an assessment of the vertical heat transport of the ISWs. The clusters of ISW packets are phase-locked to the fortnightly cycle of the semidiurnal tide. The ISWs appear during large semidiurnal tides, and there is a period of 5–6 d when no ISWs are observed. The effect of the ISWs on the continental slope heat budget is observed. The ISWs can modify a local temperature field in which the temperature in the upper layer can be changed by O(100) °C after the ISWs passed the mooring. Both ISWinduced diffusion and ISW-induced advection contribute to the temperature variation. The estimates imply an average vertical heat flux of 0.01 to 0.1 MW/m~2 in the ISWs in the upper 500 m of the water column. The vertical heat transport ranges from 0.56 to 2.83 GJ/m~2 with a mean value of 1.63 GJ/m~2. The observations suggest that the vertical heat transport is proportional to the maximum vertical displacement. 相似文献
12.
我国南海内孤立波发生频繁,由于其振幅大、流速强、能量集中等特点,已成为深海油气开发海上安装工程必须考虑的重大风险之一。依托现场守护船,提出一种内波流结构单体式监测、识别技术,采用KdV方程实现内波流预警,并成功应用于流花16-2油田群开发项目海管管线终端(PLET)安装、浮式生产储卸油装置(FPSO)锚系及水下管缆回接、空气潜水等高风险作业的内波流预警安全保障中,同时基于此次内波流预警监测结果对该海域的内波生成源和生成机制进行了探讨。应用期间采用该技术共监测、识别并发布内波预警450次。应用结果表明,约93%的内波预警时刻误差在10 min以内,平均误差为±3.90 min。统计分析结果表明,该海域的内孤立波主要来源于巴士海峡而非局地的潮地相互作用,大致可以分为两类:一类是直接产生于巴士海峡,西传至该海域;另一类是局地产生,主要是由巴士海峡产生的内波西传至陆坡浅化分裂生成或是由巴士海峡产生的内潮西传至陆坡由于非线性变陡机制产生。该内波流监测技术在流花16-2油田群开发项目的成功应用,可为南海其他类似项目提供直接的借鉴。 相似文献
13.
Chen Liang Xiong Xuejun Zheng Quanan Yuan Yeli Yu Long Guo Yanliang Yang Guangbing Ju Xi Sun Ji Hui Zhenli 《海洋学报(英文版)》2020,39(11):44-51
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. 相似文献
14.
本文基于南海东北部观测的抛物线型背景流,设计了8种形式的抛物线型背景流,利用IGW模式研究了其对内孤立波(ISW)的特征和能量学的影响。研究结果表明:背景流对波包中ISW数目没有影响,但减小了ISW的相速度;对于下边界在主温跃层附近或在其上的抛物线型背景流,ISW振幅和最大位移深度均增加;随着抛物背景流曲率减小,ISW振幅、斜压与正压能比值减小,同时ISW相速度、正压能、斜压能、KE/APE都增加;如果抛物背景流底部延伸至海底,且曲率减小,则ISW振幅、相速度减小,同时正压能、斜压能、KE/APE增加;在整个深度上的背景流,随着下层曲率减小和上层曲率增大,ISW振幅、相速度、斜压与正压能比值、斜压能、KE/APE均增加。 相似文献
15.
A European Space Agency＇ s ENVISAT advanced synthetic aperture radar （ASAR） image covering Zhejiang coastal water in the East China Sea （ECS） was acquired on 1 August 2007. This image shows that there are about 20 coherent internal solitary wave （ISW） packets propagating southwestward toward Zhejiang coast. These ISW packets are separated by about 10 kin, suggesting that these ISWs are tide-generated waves. Each ISW packet contains 5-15 wave crests. The wavelengths of the wave crests within the ISW packets are about 300 m. The lengths of the leading wave crests are about 50 km. The ISW amplitude is estimated from solving KdV equation in an ideal two-layer ocean model. It is found that the ISW amplitudes is about 8 m. Further analysis of the ASAR image and ocean stratification profiles show that the observed ISWs are depression waves. Analyzing the tidal current finds that these waves are locally generated. The wavelength and amplitude of the ECS ISW are much smaller than their counter- parts in the South China Sea （SCS）. The propagation speed of the ECS ISW is also an order of magnitude smaller than that of the SCS ISW. The observed ISWs in the ECS happened during a spring tide period. 相似文献
16.
The wide presence of internal solitary waves (ISWs) in the northern South China Sea (SCS) has been confirmed by both Synthetic Aperture Radar (SAR) images and in situ observations. These ISWs are believed being generated over the varying topography in the Luzon Strait. They typically propagate westwards into the SCS with a diurnal or semidiurnal period. Their generation sites are, however, not yet solidly identified. To obtain a clear picture of the ISWs, we designed numerical experiments to analyze the generation and propagation of the ISWs in the Luzon Strait using a 2-dimensional non-hydrostatic model. The model current is forced by barotropic or baroclinic currents imposed at open boundaries. The experiments show that the tidal current serves as a kind of triggering force for the ISWs over the submarine ridges in the strait. Under the forcing of tidal currents, depressions are formed near the ridges. The ISWs then split from the depressions through a process different from lee-wave generation mechanism. The appearance of the ISWs is influenced by the strength and period of the forcing current:the ISWs are more likely to be generated by a stronger tidal current. That is why the ISWs in the Luzon Strait are frequently observed during spring tide. Compared with diurnal tidal current, the ISWs generated by semidiurnal tidal current with the same amplitude is much more energetic. It is partly because that the wave beams in diurnal frequency have a larger angle with the vertical direction, thus are more likely to be reflected by the topography slope. The impact of the Kuroshio to the ISWs is also analyzed by adding a vertical uniform or shear current at boundaries. A vertically uniform current may generate ISWs directly. On the other hand, a vertically shear current, which is more realistic to represent the Kuroshio branch, seems to have little influence on the generation process and radiating direction of the ISWs in the Luzon Strait. 相似文献
17.
A new method to estimate phase speed and vertical velocity of internal solitary waves in the South China Sea 总被引：2，自引：0，他引：2
A new method of estimating the phase speed and vertical velocity of internal solitary waves (ISW) based on dynamic governing equations using Acoustic Doppler Current Profiler (ADCP) data was developed. This method was applied to a representative ISW case, which was captured in the South China Sea in the 2007 summer experiment. The result shows that this ISW had a phase speed of approximately 2.6?m?s?1. This method provides an excellent alternative in estimating the phase speed of ISWs, especially useful in the absence of vertical stratification needed in solving the Korteweg–de Vries (KdV)-type equation, e.g., long-term mooring observation. Analyses show that the new method is fairly self-consistent, and it can be applied when only a part of the ISW observations is available. The computed vertical velocity of the ISW using the new method has a good agreement with the ADCP observations both in magnitude and pattern. 相似文献
18.
Mooring observations of internal solitary waves in the deep basin west of Luzon Strait 总被引：6，自引：3，他引：3
A total of 137 internal solitary waves （ISWs） are captured during a field experiment conducted in the deep basin west of the Luzon Strait （LS） from March to August, 2010. Mooring observations reveal that a fully developed ISW owns a maximum westward velocity of more than 1.8 m/s and an amplitude of about 200 m. The ISWs in the South China Sea （SCS） are most active in July, which may be due to the strong stratification in summer. Most of the ISW episodes are detected around and after the 1st or 15th lunar day, indicating that the ISW in the SCS is triggered by astronomic tides. Half part of the observed ISWs were detected around 19：00 local time, which can be explained by the fact that type-a ISWs emerged in the evening at roughly the same time each day. The propagation direction of the ISWs and the astronomic tides in the LS show that the area south of the Batan Island is probably the main source region of the type-a ISWs, while the area south of Itbayat Island and south of the Batan Island is likely the main source region of the type-b ISWs observed at the mooring. Moreover, for the resonance of semidiurnal internal tides emitting from the double ridges in the LS, the underwater ridge south of the Itbayat Island and south of the Batan Island is believed to favor the generation of the energetic ISWs. 相似文献