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<正>On 21 April 2021 local time(20 April UTC), the Indonesian Navy submarine(KRI Nanggala-402) sank near the Lombok Strait, ～100 km north of the Bali Island(see magenta star in Fig. 1a),with 53 crew members dead. On the basis of Moderate Resolution Imaging Spectroradiometer(MODIS) satellite images(Jackson, 2007), 相似文献
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南海东北部受黑潮入侵、季风等动力因素的影响,背景剪切流场复杂,涡旋众多,水体垂向层结季节性变化明显,同时又因吕宋海峡的复杂底地形和强潮流的影响,内潮、内孤立波现象显著。但是,以往关于内潮、内孤立波的研究很少考虑到背景剪切流场和涡旋对其影响,因而难以揭示内波的生成、传播和演变规律。主要概述了南海东北部的剪切流、涡旋和内波等多种中尺度物理现象及其之间的相互作用的研究进展,进而提出未来关于南海东北部剪切流场对内波生成、传播和演变影响研究中的一些问题和研究思路。 相似文献
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A continuously stratified nonlinear model is set up to study the impact of topographical character on the generation of internal solitary waves over a sill by tidal flow. One of the reasons why almost all of the generated internal solitary waves propagate westward in the northern South China Sea is explained. The model simulations describe the generation and propagation of internal waves well. When the strength of imposed barotropic tides and the water stratification stay unchanged, the steepness of the sill slope can control both (a) whether or not the waves induced over a sill by tidal flow are linear internal waves or nonlinear internal solitary waves, and (b) the amplitude of the internal solitary waves generated. If the steepness of the sill is asymmetric, the nonlinear internal solitary waves may be induced on the steeper side of the sill. These conclusions are supported by a numerical experiment with a monthly-mean stratification and an actual seafloor topography from the Luzon Strait. 相似文献
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There are few studies on the variation of Froude number versus depth during the passage of internal solitary waves (ISWs). In this paper, according to the limited observational data of the ISWs near the Dongsha Islands in the northern South China Sea (SCS), it is found that, during the passage of an ISW, the local Froude number near the main thermocline gets maximum and the flow is supercritical, with the Froude number decreasing gradually upward and downward, whilst before and after the passage of the ISW, the local Froude number is less than 1 and the flow is subcritical in the entire water column. Since the observational current data are only available in the upper ocean, a two-dimensional continuously stratified nonlinear model is employed here to study the variation of Froude number versus depth during the passage of an ISW. The modeled ISW induced current field agrees well with that observed during the passage of the observational ISW. It is found that, even during the passage of the ISW, although the Froude number is larger than 1 in the upper layer, it is less than 1 in the lower layer, and the duration when the Froude number is larger than 1 also changes with depth. Thus, it is suggested that, once the Froude number near the main thermocline is larger than 1, the passage of ISWs could be identified. Moreover, it would be better to choose a sampling interval of no more than 1/4 passage period of the ISW during an in-situ observation of ISWs. 相似文献
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Direct numerical simulations are performed to investigate the generation of internal waves by tide-topography interaction in a lab-scale model. The bottom topography is a triangular ridge with two critical slopes. With increasing tidal forcing, subharmonic instabilities are identified, which cause internal wave beams to become unstable and turbulent. Kinetic energy densities in the upward going beams from the ridge top are stronger than those from the ridge bottom, whereas the reverse is true for the energy flux. This disparity between energy and energy flux is due to the existence of strong pressure disturbances near the ridge bottom. On each side of the critical ridge, there exists an amphidromic point, from which internal wave beams are emitted in opposite directions. The calculated energy conversion rate scales linearly with the square of the forcing amplitude and agrees within 13% of theoretical prediction, even when turbulence occurs. The fraction of radiated baroclinic energy becomes saturated in the range of low excursion parameter considered, which agrees with the behavior in large-scale systems wherein mixing parameterizations must be used. The present work enriches the studies on the generation of internal waves over a critical triangular ridge. 相似文献
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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
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The horizontally variable density stratification and background currents are taken into the variable-coefficent extended Korteweg-de Vries(evKdV) theory to obtain the geographical and seasonal distribution of kinematic parameters of internal solitary waves in the Andaman Sea(AS). The kinematic parameters include phase speed,dispersion parameter, quadratic and cubic nonlinear parameters. It shows that the phase speed and dispersion parameter are mainly determined by the topographic feature and ha... 相似文献
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季节性层结对孤立内波作用于圆柱载荷的影响 总被引：1，自引：0，他引：1
On the basis of Morison＇s empirical formula and modal separation method in estimating the force and torque exerted by internal solitary waves （ISWs） on a cylindrical pile, it is found that the loads exerted by the ISWs change largely in different seasons at the same site of the continental shelf in the South China Sea （SCS） even under the condition that the amplitudes of ISWs are the same. Thus, the effect of a seasonal water stratification variation on the force and torque exerted by the ISWs is investigated, and a three-parameter stratification model is employed. It is shown that the loads exerted by the ISWs depend largely on the wa- ter stratification. The stronger the water stratification, the larger the force and the torque; when the depth where the maximum thermocline appears is deepened, the force decreases but the torque increases; when the width of the thermocline is narrowed, the force increases but the torque decreases. The seasonal varia- tion of the force and the torque exerted by the ISWs in four seasons in the SCS is thus explained. Key words： internal solitary waves, force, torque, water stratification, South China Sea 相似文献
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An Overview of Internal Solitary Waves in the South China Sea 总被引：7，自引：0，他引：7
Internal solitary waves (ISWs) are the nonlinear large amplitude waves existing in the oceanic pycnocline. They are very active in the northern South China Sea (SCS). With more and more remote sensing data, in situ observational data and the development of the numerical simulation technology, a number of studies on the characteristics, the source site, the generation, and evolution of the ISWs in the SCS are reported. In this paper, earlier studies on the ISWs in the SCS are summarized and some problems worthy of study are put forward. 相似文献