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1.
文章基于2011年9～11月南海西沙潜标观测资料,研究了西沙海域上层海洋对连续台风Nesat(1117)和Nalgae(1119)过境的近惯性响应.结果表明:两个台风过境都产生了强烈的近惯性振荡,且台风路径右侧的近惯性流速明显大于左侧. Nesat引起的近惯性内波平均垂向相速度为0.25cm s~(-1),垂向群速度为0.85m h-1,垂向波长为350m.Nalgae所引起的近惯性内波垂向相速度和群速度均小于Nesat,垂向波长仅为Nesat的1/2.两个台风引起的近惯性能量下传深度存在明显差异, Nalgae约为200m,而Nesat可下传至300m.产生这一差异的主要原因是Nesat引起的近惯性能量不易耗散,同时能够以较快的速度向深海传播.此外,两个台风引起的近惯性内波频率都存在明显的蓝移现象. Nesat引起的近惯性内波频率在100～150m深度受多普勒频移的影响明显增大;然而Nalgae引起的近惯性内波频率却在100～150m深度显著减小,这是由于两个台风过境期间,西沙海域背景场涡度差异所致. 相似文献
2.
从包含Ｒｏｓｓｂｙ波和惯性重力波的大气运动方程组出发，采用弱非线性相互作用近似，推导出耗散大气中这两种尺度相差很大的波动之间的非线性相互作用方程．以此为基础，得到了描述窄角谱Ｒｏｓｓｂｙ波包和惯性重力波包的非线性时空演变规律的三波相互作用方程．数值分析表明，当一个Ｒｏｓｓｂｙ波包与两个惯性重力波包发生相互作用时，两个惯性重力波包之间进行快速的能量交换，同时与Ｒｏｓｓｂｙ波包之间进行缓慢的能量传输．从时间尺度上讲，惯性重力波可以看作Ｒｏｓｓｂｙ波包运动的背景噪声，因此上述非线性相互作用过程可以理解为大尺度Ｒｏｓｓｂｙ波包与背景噪声之间的能量交换过程． 相似文献
3.
本文主要讨论在导致赤道夜间扩展F回波的上升汽泡中,短波区（λ25m）等离子体密度谱分布的物理机制,说明不均匀体内不同的湍动水平将产生不同的谱结构。对于较低湍动水平的汽泡,由于纵向离子声波和具有有限平行波矢漂移波的耦合共振相互作用,导致波模间能量的有效传输,从而控制湍动水平的发展,形成等能多峰谱结构。另一方面,对于湍动充分发展的汽泡,由长波区大幅度扰动维持的短波区强漂移湍动态,在KrLi≈2处形成一较宽的极大谱峰,然后谱以K-2.6的形式减小。理论分析和探测结果符合甚好。 相似文献
4.
《地震工程与工程振动》2016,(4)
为了研究地震作用下AP1000核电厂重力水箱的减震作用。本文基于任意拉格朗日欧拉流固耦合算法,建立AP1000核电厂屏蔽厂房重力水箱8种水位工况的全耦合精细有限元分析模型,分析满足RG1.60反应谱的核电人工波作用下重力水箱的动力响应,参数化分析屏蔽厂房不同位置的加速度和位移响应与水箱水位高度、空气高度、水位高度比以及水箱振荡频率之间的相互作用规律和机制,探究核电厂重力水箱的最优减震水位。计算结果表明:在满足核电厂供水的条件下,当水位为工况3,水位高度为8.8 m,水位高度比为0.75时,AP1000核电厂屏蔽厂房动力响应最小,减震效果最优。 相似文献
5.
0.003~1 Hz频段的地脉动主要来源于海浪运动与固体地球的耦合作用,台风引起的强烈海浪运动往往可使地脉动能量显著增强.由于涉及大气-海洋-固体地球三个圈层之间的复杂动量传递与耦合过程,迄今为止,关于台风激发地脉动的具体源区位置及激发机制尚存在争议.本文选取日本、中国东南沿海及台湾地区的地震台站波形连续记录,研究了2008年台风"森拉克"和"黑格比"激发地脉动的时频特征,开展相应数值模拟,并与观测数据进行了对比分析研究.结果表明台风激发第二类地脉动存在两种主要模式:(1)近岸源区激发,即台风引起波浪入射至海岸反射并与后续来波相互作用形成驻波作用于海底而激发;(2)台风中心附近源区激发,即台风中心移动过程中不同时期激发的同频率波浪相向传播、相互作用产生驻波作用于海底而激发,源区位置主要集中于台风中心左后方.此外,结合波浪再分析数据、台风风场特征,我们进一步对第二类地脉动激发过程中的影响因素进行了分析,发现:第一种模式激发的地脉动与近岸源区波浪场强度、观测点至源区距离及台风中心至海岸线距离等因素相关;而第二种模式激发的地脉动则主要受台风中心附近波浪场的频率成分与传播方向影响. 相似文献
6.
根据实际观测资料反演获得描述大气环流演变的空间谱函数后，从改进的高截断谱模式途径出发研究了夏季东北亚阻塞高压年际变化的物理机制.结果表明，前期外部热源强迫的空间分布大致为El Nio型分布时，外部热力强迫导致大气环流演变中波波相互作用主要表现为纬向2波的相互作用；波流相互作用主要表现为经向2波和3波与反映基本流中的经向1波的相互作用.这样使得500 hPa高度场上东北亚地区为一相对正异常区，为夏季东北亚阻塞的频繁发生提供了有利的大气环流背景.而前期外部热源强迫大致为La Nia型分布时，外部热力强迫则导致大气环流演变中波波相互作用主要表现为纬向1波的相互作用；波流相互作用主要表现为经向2波和4波与反映基本流中的经向2波的相互作用.从而使得500 hPa高度场上帆北亚地区出现相对负异常，抑制了夏季东北亚阻塞的发生. 相似文献
7.
对布设在南北构造带南段的中国地震科学探测台阵项目一期350个宽频带流动台站和中国地震台网90个宽频带固定台站记录的远震XKS(SKS、SKKS和PKS)波形资料作偏振分析,采用最小切向能量的网格搜索法和"叠加"分析方法求得每一个台站的XKS波的快波偏振方向和快、慢波的时间延迟,获得了南北构造带南段上地幔各向异性图像.结果显示研究区的各向异性具有明显的南北分区特征,北部的快波方向为近N-S方向,而南部主要表现为近E-W方向,且北部的平均时间延迟小于南部.分析表明,具有厚岩石圈的北部的各向异性主要由岩石圈变形引起,是一种垂直连贯变形模式;具有薄岩石圈的南部的各向异性主要由软流圈地幔流引起,缅甸和巽达板片的后撤/回转作用产生了指向西南的软流圈地幔流,在岩石圈底部和软流圈之间产生了一个水平差异运动,产生了一个与简单剪切一致的软流圈变形结构,从而产生了南部观测的各向异性. 相似文献
8.
通过对佘山台四分量钻孔应变仪在台风“浣熊”(Neoguri)和“海葵” (Haikui)经过期间所记录的信号进行小波分解、连续频谱分析以及优势振动方向计算，监测到台风对近岸造成显著低频扰动，并分析了扰动信号在时间空间频率域的影响特征，在此基础上探讨了扰动的激发机制.分析结果显示:在台风发育过程中，覆盖周期为2—16分钟的3个频段能量呈现显著的上升—峰值—下降规律，且这种升降变化与台风中心到台站之间的距离具有良好的相关性，其中周期2—4分钟为扰动的优势频段，能量幅值则随周期的增大而不断减弱.四分量钻孔应变仪在两次台风逼近期间的优势振动方向均为160°左右.通过对比风速数据，结合海岸地形，认为风对陆地的作用并不是引起低频扰动的主要原因，更可能是台风以海浪为介质，通过不断与呈光滑凹形形态的杭州湾北部海岸线的反射作用，进而激发自由振荡频段的低频扰动信号. 相似文献
9.
本文利用f-平面浅水模型讨论了二维情况下快速惯性重力波与平衡涡旋之间的相互作用问题.当快速的惯性重力波传入涡旋区域后，波－涡之间发生了相互作用，涡旋可被加深，涡旋区域的风场等可以出现非对称分布，当惯性重力波全部传出涡旋区域并远离之后，涡旋恢复到其初始状态，但此时惯性重力波可以出现非对称结构，这与一维情况不同.在波－涡发生相互作用过程中，其物理量变化的最大区域分布基本与波动传播方向一致，在波动进入或移出涡旋时，相对应存在两个最大物理量变化区域，此外，相互作用导致的物理量的最大变化与波动结构、强度、传播方向以及涡旋特性有关.非线性条件下的波－涡相互作用要强于线性过程. 相似文献
10.
通过将山东地区GPS 观测结果与穿透整个岩石圈的SKS 剪切波分裂及近场资料剪切波分裂的快波方向相比较,来探讨山东地区壳幔运动的耦合作用。结果发现,地壳内近场快剪切波偏振与SKS 快剪切波偏振总是相差十几度以上,这种差异可能说明,山东地区壳幔之间构造活动可能有一定程度的解耦,表明山东地区的壳幔运动耦合作用可能既不是壳幔强耦合型,也不是简单的壳幔解耦型,该地区的壳幔运动耦合作用可能是2 种模式共存的不均匀分布或者是物理性质介于两者之间的渐变模式,这与早先对华北地区的类似研究获得的结论相同。 相似文献
11.
Ocean Dynamics - Previous studies have indicated that internal tides (ITs) in the South China Sea (SCS) are dominated by the M2, K1, and O1, among which intense nonlinear interaction occurs. In... 相似文献
12.
基于海南岛至西沙群岛之间深水海域一长达5年的锚定潜标测流资料,采用谱分析、调和分析和动力模态分解等方法主要分析了局部海域内潮的基本特征.结果表明:研究海域的正压和斜压潮均以全日振荡为主,500~900m的海洋中层全日等密度线垂向振幅可达40m;全日内潮主要沿垂直于陆坡方向传播,与天文潮锁相的全日内潮可占全日内潮总能量的41%;海洋上层,O1内潮垂向平均振幅与局地海面高度呈显著正相关关系,K1内潮则表现为夏、冬季增强的半年循环特征;超过70%的O1分潮能量集中于第一、二斜压模态上,K1分潮在第三斜压模态上亦有相当能量. 相似文献
13.
已有的内波研究多来自单点的垂直剖面观测资料,但研究内波水平特征的实测资料却非常缺乏．利用反射地震方法研究海水温盐结构,具有高水平分辨率和短时间内对整个海水垂直剖面进行成像的优势,能够弥补传统物理海洋学观测方法的缺陷,为研究海洋内波提供有前景的新手段．本文通过对南海东北部地震剖面的重新处理、分析,认为地震叠加剖面上同相轴呈现的起伏变化反映了内波的总体形态．计算的水平波数能量密度谱与GM76模型谱基本一致,但在低波数段和高波数段中,两者的振幅及斜率存在着一定差异,经分析认为这种差异主要与内潮波和复杂海底地形的强烈非线性相互作用以及内波破碎等因素有关 相似文献
14.
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
15.
During 9–16 November 2001 the western Mediterranean Sea was lashed by one of the most extreme storms of the last decades. Current meter data from seven moorings in the Palamós submarine canyon (northwestern Mediterranean) are analyzed to understand the vertical propagation of near-inertial energy generated by the storm. The daily inertial rotary components are examined for evidence of free and forced near-inertial oscillations. Free near-inertial motions are increased during the storm, although they are larger outside the canyon than inside. Conversely, forced near-inertial motions are relatively large inside the canyon but are almost negligible outside. Based on the results of a three-dimensional ocean circulation model, these differences are shown to be caused by the presence of a storm-generated alongshore front. The mechanisms by which near-inertial energy propagates are distinct at each side of the front. On the onshore side of the front (inside the canyon), free near-inertial motions are rapidly carried away by normal inertial waves, and wave reflection off canyon wall is responsible for the dissipation of free near-inertial motions and enhancement of forced near-inertial motions. On the offshore side of the front (outside the canyon), on the other hand, free near-inertial motions propagates first downward with anomalously low frequency internal waves and are then advected southward and offshore by the mean flow. 相似文献
16.
利用地震海洋学方法研究海洋内波已成为海洋地球物理学家与物理海洋学家共同关注的前沿问题.本文尝试利用当今时频分析的新手段——希尔伯特-黄变换中的经验模态分解（EMD）方法对南海东北部地震数据处理获得的垂直位移分布数据进行分解,获得了一些有新意的结果.分解结果表明,南海东北部海盆上方区域的内波包含波长约1.2、2.5、4、12.5 km的组成成分,其中波长约1.2、2.5 km的内波在200~1050 m的深度范围内上、下各层的波动基本耦合;波长约4 km与12.5 km的内波以600~700 m的水层为分界,其上、下部分的内波相位差90°,指示低波数内波能量的斜向传播.这些研究表明,EMD方法在内波运动学特征的地震海洋学研宄方面有良好的应用前景. 相似文献
17.
Naresh Krishna Vissa A. N. V. Satyanarayana B. Prasad Kumar 《Pure and Applied Geophysics》2013,170(12):2369-2381
In the present study, an attempt was made to understand the role of South China Sea (SCS) convection associated with northerly cold surges and Typhoon Peipah in initiating Cyclone Sidr in the Bay of Bengal (BoB). The variation of air sea fluxes during the entire history of Cyclone Sidr tracking before its landfall over Bangladesh was also studied. The presence of cold surges in the north SCS associated with heavy rainfall episodes has been noticed at the southern Gulf of Tonkin coast prior to the formation of Typhoon Peipah. Subsequently, these surges migrated south, which resulted in intensification of a deep convection on reaching the Vietnamese coast. During the same period in the western Pacific, Typhoon Peipah developed, propagating in the westward direction and entering the SCS. Analysis of geostationary water vapour images, mean sea level pressure, and surface wind maps clearly depicted the transport of convective cloud clusters, moisture, and westward momentum from Typhoon Peipah to the deep convection cells over the SCS. Consequently, the existing deep convection over the Vietnamese coast resulted in a westward direction and entered the Gulf of Thailand and Andaman Sea. The availability of higher latent heat fluxes, warmer sea surface temperatures, and suitable atmospheric conditions over this region favoured the formation of a tropical depression in the Andaman Sea. This depression further intensified in the southeast BoB, resulting in the formation of Cyclone Sidr. NCEP/NCAR wind fields and air-sea fluxes revealed left asymmetry surface winds and higher latent heat flux on the left side of the track during the intensification phase of Sidr. 相似文献
18.
Robin Robertson 《Ocean Dynamics》2011,61(1):69-88
Interactions of tidal constituents and the transfer of energy from the tidal frequencies to other frequencies are investigated
using 3-D tidal simulations for the Indonesian seas, focusing on an area of active internal tides. Semidiurnal tides strongly
affect diurnal tides; however, semidiurnal tides are essentially unaffected by diurnal tides. The semidiurnal and diurnal
constituents interact with each other through non-linear interference, both destructive and constructive. Semidiurnal tides
generate harmonics at nearly the diurnal frequency and higher vertical wavenumbers. In Ombai Strait, these harmonics are out
of phase with the diurnal tides and interact destructively with the diurnal tides, effectively negating the diurnal response
in some locations. However, this is not a general response, and interactions differ between locations. Energy is also transferred
from both semidiurnal and diurnal tides to other frequencies across the spectrum, with more energy originating from semidiurnal
tides. These energy transfers are not homogeneous, and the spectral responses differ between the Makassar and Ombai Straits,
with the region east of Ombai showing a more active surface response compared to a more intense benthic response in Makassar.
In deep water away from topography, velocity spectra generally follow the Garrett–Munk (GM) relation. However, in areas of
internal tide generation, spectral density levels exceed GM levels, particularly between 4 and 8 cycles per day (cpd), indicating
increased non-linear interactions and energy transfer through resonant interactions. The model indicates strong surface trapping
of internal tides, with surface velocity spectra having significantly higher energy between 4 and 8 cpd even 100 km away from
the prominent sill generating the internal tides. 相似文献
19.
Sea breezes are characteristic features of coastal regions that can extend large distances from the coastline. Oscillations close to the inertial period are thought to account for around half the kinetic energy in the global surface ocean and play an important role in mixing. In the vicinity of 30°N/S, through a resonance between the diurnal and inertial frequencies, diurnal winds could force enhanced anti-cyclonic rotary motions that contribute to near-inertial energy.Observations of strong diurnal anti-cyclonic currents in water of depth 175 m off the Namibian coastline at 28.6°S are analysed over the annual cycle. Maxima in the diurnal anti-cyclonic current and wind stress amplitudes appear to be observed during the austral summer. Both the diurnal anti-cyclonic current and wind stress components have approximately constant phase throughout the year. These observations provide further evidence that these diurnal currents may be wind forced. Realistic General Ocean Turbulence Model (GOTM) 1-D simulations of diurnal wind forcing, including the first order coast-normal surface slope response to diurnal wind forcing, represent the principal features of the observed diurnal anti-cyclonic current but do not replicate the observed vertical diurnal current structure accurately. Cross-shelf 2-D slice simulations suggest that the first order surface slope response approximation applies away from the coast (>140 km). However, nearer to the coast, additional surface slope variations associated with spatial variations in the simulated velocity field (estimated from Bernoulli theory) appear to be significant and also result in transfer of energy to higher harmonics. Evidence from 3-D simulations at similar latitude in the northern hemisphere suggests that 3-D variations, including propagating near-inertial waves, may also need to be considered. 相似文献
20.
A three-dimensional baroclinic model of the Balearic Sea region is used to examine the processes influencing the distribution of near-inertial currents and waves in the region. Motion is induced by a spatially uniform wind impulse. By using a uniform wind, Ekman pumping due to spatial variability in the wind is removed with the associated generation of internal waves. However, internal waves can still be produced where stratification intersects topography. The generation and propagation of these waves, together with the spatial distribution of wind-forced inertial oscillations, are examined in detail. Diagnostic calculations show that in the near-coastal region inertial oscillations are inhibited by the coastal boundary. Away from this boundary the magnitude of the inertial oscillations increases, with currents showing a 180° phase shift in the vertical. The inclusion of an along-shelf flow modifies the inertial currents due to non-linear interaction between vorticity in the flow and the inertial oscillations. Prognostic calculations show that besides inertial oscillations internal waves are generated. In a linear model the addition of an along-shelf flow produces a slight reduction in the energy at the near-inertial frequency due to enhanced viscosity associated with the flow and changes in density field. The inclusion of non-linear effects modifies the currents due to inertial oscillations in a manner similar to that found in the diagnostic model. A change in the effective inertial frequency also influences the propagation of the internal waves. However, this does not appear to be the main reason for the enhanced damping of inertial energy, which is due to the along-shelf advection of water of a different density into a region and increased viscosity and mixing associated with the along-shelf flow.Responsible Editor: Phil Dyke 相似文献