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1.
基于2014年8-9月南海北部东沙群岛附近海域两个临近站位(站位A,20.736°N,117.745°E,水深1 249 m;站位B,20.835°N,117.56°E,水深848 m)的潜标数据,研究了台风过境所激发的近惯性振荡的特征,分析了中尺度暖涡对近惯性频率的调制及其对近惯性动能分布和传播的影响。站位A(B)142(175) m以浅,近惯性频率由0.710 1(0.713 3)周/d红移至0.659 2周/d,频率减小了7.2%(7.6%),观测结果与两个站位所处的背景涡度相吻合。中尺度暖涡改变了水体层结状态,两个站位的近惯性动能在不同层结中被改变了0.5~3倍。水体层结对能量的折射作用使得站位B的近惯性动能在深度158~223 m之间衰减较少,而站位A的近惯性动能则随着深度的增加快速减小。站位A和站位B近惯性内波的垂向群速度分别约为15.2 m/d和14.1 m/d。如果忽略近惯性动能的水平辐散,近惯性内波的垂向传播分别造成了两个站位垂向上约47%和38%的近惯性动能衰减。 相似文献
2.
《热带海洋学报》2018,(6)
文章利用2014年9月南海东北部附近海域的A、B两个相距约20km的潜标数据,分析了台风"海鸥"在南海东北部激发的近惯性振荡的垂向分布特征。结果表明,台风过境在两站点激发了强烈的近惯性振荡,其能量由海表向海洋内部传播;近惯性能量在表层随着深度增加而增大,最大值出现在次表层,此后随着深度增加迅速衰减。但是两个观测站点的近惯性振荡垂向分布特征有较大的差别:A站点的近惯性振荡在不同深度上存在三个不同的垂向相速度,而B站点的垂向相速度没有变化;两站点的最大近惯性动能的大小及其所在深度不同,B站点比A站点的最大近惯性动能大15%左右。台风过后两个站点均出现由近惯性波f和半日内潮波D_2非线性相互作用产生的次级波动fD_2,但其强度存在差异。台风后A站点fD_2在不同深度上有不同的变化,f和D_2相互作用较弱;而B站点的fD_2在整个近惯性振荡影响深度内都是增强,其fD_2和f频带的动能和流速在时空分布以及变化趋势上有较好的相关性。两站点的近惯性振荡垂向相速度以及次级波动fD_2的不同可能是水体层结的差异和涡旋的影响所导致的。 相似文献
3.
文章利用2014年9月南海东北部附近海域的A、B两个相距约20km的潜标数据, 分析了台风“海鸥”在南海东北部激发的近惯性振荡的垂向分布特征。结果表明, 台风过境在两站点激发了强烈的近惯性振荡, 其能量由海表向海洋内部传播; 近惯性能量在表层随着深度增加而增大, 最大值出现在次表层, 此后随着深度增加迅速衰减。但是两个观测站点的近惯性振荡垂向分布特征有较大的差别: A站点的近惯性振荡在不同深度上存在三个不同的垂向相速度, 而B站点的垂向相速度没有变化; 两站点的最大近惯性动能的大小及其所在深度不同, B站点比A站点的最大近惯性动能大15%左右。台风过后两个站点均出现由近惯性波f和半日内潮波D2非线性相互作用产生的次级波动fD2, 但其强度存在差异。台风后A站点fD2在不同深度上有不同的变化, f和D2相互作用较弱; 而B站点的fD2在整个近惯性振荡影响深度内都是增强, 其fD2和f频带的动能和流速在时空分布以及变化趋势上有较好的相关性。两站点的近惯性振荡垂向相速度以及次级波动fD2的不同可能是水体层结的差异和涡旋的影响所导致的。 相似文献
4.
《热带海洋学报》2020,(2)
文章利用经验台风风场模型(TCWPM)和美国环境预测中心的气候预测系统再分析风场资料(NCEP/CFSR)对台风"康森(Conson)"进行数值模拟,并将模拟的台风带入平板模式(slab model)模拟台风产生的海洋近惯性流。对比实测数据表明,模拟结果与真实风场、近惯性流场均比较一致,台风"康森"在近海面的风场不对称结构非常明显,台风中心两侧的速度大小相差可达10m·s~(–1)。台风"康森"在台风中心后方产生强烈的海洋近惯性振荡,且持续时间超过4d。海洋近惯性动能沿着台风路径呈显著的不对称分布,表明台风"康森"在共振作用下主要在路径右侧激发强烈的近惯性振荡。研究不同强度的热带气旋产生的海洋近惯性能量,发现热带风暴产生的海洋近惯性能量较小,平均近惯性动能不超过35J·m~(–3)。随着气旋强度的增大,热带气旋激发的近惯性能量呈指数增长,而台风的影响面积与最大风速半径的变化相对比较一致,当最大风速半径(R0)增大一半(1.5R0)时,其产生的最大平均近惯性动能从81J·m~(–3)增大到631J·m~(–3),影响面积从大约600km~2增加到大于900km~2。 相似文献
5.
近惯性内波广泛存在于全球海洋,是维持深层海洋跨等密度面湍流混合及海洋层结的重要能量来源。基于黑潮-亲潮混合区的多年深海潜标数据,分析了:(1)该海域近惯性内波及其能量的季节变化特征与影响因素,(2)上层和深层近惯性运动的频率、波数谱及垂向分布等特征。结果表明,该海域存在丰富的近惯性动能,无论海洋上层还是深层均呈现显著的冬季强、夏季弱的季节变化特征,冬季(12～2月)上层的近惯性能量可占全年能量的41%,深层近惯性信号同样显著,同潮汐信号相当。平板模型分析表明,该区域近惯性动能的季节循环特征主要受风场的季节变化所主导,同时受到黑潮延伸体流轴的摆动调制。 相似文献
6.
文章利用经验台风风场模型(TCWPM)和美国环境预测中心的气候预测系统再分析风场资料(NCEP/CFSR)对台风“康森(Conson)”进行数值模拟, 并将模拟的台风带入平板模式(slab model)模拟台风产生的海洋近惯性流。对比实测数据表明, 模拟结果与真实风场、近惯性流场均比较一致, 台风“康森”在近海面的风场不对称结构非常明显, 台风中心两侧的速度大小相差可达10m·s-1。台风“康森”在台风中心后方产生强烈的海洋近惯性振荡, 且持续时间超过4d。海洋近惯性动能沿着台风路径呈显著的不对称分布, 表明台风“康森”在共振作用下主要在路径右侧激发强烈的近惯性振荡。研究不同强度的热带气旋产生的海洋近惯性能量, 发现热带风暴产生的海洋近惯性能量较小, 平均近惯性动能不超过35J·m-3。随着气旋强度的增大, 热带气旋激发的近惯性能量呈指数增长, 而台风的影响面积与最大风速半径的变化相对比较一致, 当最大风速半径(R0)增大一半(1.5R0)时, 其产生的最大平均近惯性动能从81J·m-3增大到631J·m-3, 影响面积从大约600km2增加到大于900km2。 相似文献
7.
《中国海洋大学学报(自然科学版)》2016,(6)
本文基于布放于南海北部的ADCP海流数据和温度链数据,分析了南海北部上层海洋对强台风尼格响应特征。结果表明:台风活动会生成强烈的近惯性振荡;在热力学方面会引起南海北部海区特别是表层海水迅速降温,海温的日变化特征消失;动力学方面近惯性内波成为支配研究海区海水流动的关键因素,造成流速迅速增大;此外近惯性内波会向下传播,并且下传时经历由慢至快的过程;最后近惯性内波会引起波-波相互作用,包括近惯性内波的入射和反射波之间相互作用生成频率两倍于惯性频率的内波,以及近惯性振荡与半日内潮相互作用生成两者频率之和的波动,使近惯性能量发生转移。 相似文献
8.
近惯性波广泛存在于全球海洋,对海洋中的能量级联非常重要。风输入海洋的近惯性能量在海洋中是如何传播和耗散的,能量在海洋中如何划分,一直是受到高度关注的话题。本文简要综述了风生近惯性波在海洋中的传播和耗散过程,包括影响近惯性波传播的因素,比如β效应、中尺度涡度、台风尾流和近惯性波自身的波数特征等;近惯性波在风暴等强天气过程下的传播方式;近惯性波在混合层中衰减时间尺度的模拟;近惯性能量在海洋中的分配以及现有研究中还未解决的问题。本文拟为今后的近惯性波研究提供一些思路,进一步促进近惯性波机制和模拟等方面研究的深入开展。 相似文献
9.
本文利用在菲律宾海布放的一套锚系潜标获取的长时间海流和水温观测数据，分析了吕宋海峡以东的深海海洋环境特征，着重阐释了该海域海流的全水深垂向结构及其低频变化特征。研究表明，表层(100～160 m)平均流向为西偏北，流速约为12.5 cm/s；中层(810 m)的平均流为西向，流速为2.6 cm/s；深层(1 550 m和2 560 m)的平均流速在1 cm/s以内，近底(4 040 m)的流向为较稳定的西南向，流速为2.3 cm/s。上层海流的动能比中层和深层大1～2个量级，总动能、平均动能、涡动动能均在表层最大，中层次之、深层最小，各层次涡动能均大于平均动能。中上层海流的低频变化具有极高的相似性，全年为81～85 d的周期振荡；近底层海流则不同，变化周期约为51 d。 相似文献
10.
基于2011年4月至2012年3月南海北部陆坡区潜标观测的高分辨率流速数据,本文研究了海洋上层细尺度流速剪切的时间变化特征及其演变规律。流速剪切的功率谱分析结果显示,南海北部上层的细尺度流速剪切主要受亚惯性运动、近惯性内波、全日内潮和半日内潮四种过程控制。其中,风生近惯性内波和中尺度涡旋所对应的亚惯性运动是造成上层流速剪切时间变化的主要原因,以往研究强调的全日和半日內潮的贡献则相对较弱。进一步分析发现,冬季中尺度暖涡能够极大地增强海洋上层的亚惯性剪切;夏、秋季南海活跃的台风所激发的近惯性内波能够造成近惯性剪切增强。另外,研究还发现,背景涡度对近惯性剪切具有重要的调制作用,即负涡度相较于正涡度更有利于近惯性剪切增强。该研究所揭示的流速剪切的时间变化规律及调控机制对改进海洋混合的参数化方案具有重要的参考价值。 相似文献
11.
Recent numerical studies (Hibiya et al., 1996, 1998, 2002) showed that the energy cascade across the internal wave spectrum down to small dissipation scales was
under strong control of parametric subharmonic instabilities (PSI) which transfer energy from low vertical mode double-inertial
frequency internal waves to high vertical mode near-inertial internal waves. To see whether or not the numerically-predicted
energy cascade process is actually dominant in the real deep ocean, we examine the temporal variability of vertical profiles
of horizontal velocity observed by deploying a number of expendable current profilers (XCPs) at one location near the Izu-Ogasawara
Ridge. By calculating EOFs, we find the observed velocity profiles are dominated by low mode semidiurnal (∼double-inertial
frequency) internal tides and high mode near-inertial internal waves. Furthermore, we find that the WKB-stretched vertical
scales of the near-inertial current shear are about 250 sm and 100 sm. The observed features are reasonably explained if the
energy cascade down to small dissipation scales is dominated by PSI. 相似文献
12.
南海西北陆坡区内潮与近惯性内波观测研究 总被引：2，自引：2，他引：0
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。 相似文献
13.
Using a two-dimensional primitive equation model, we examine nonlinear responses of a semidiurnal tidal flow impinging on
a seamount with a background Garrett-Munk-like (GM-like) internal wavefield. It is found that horizontally elongated pancake-like
structures of high vertical wavenumber near-inertial current shear are created both in the near-field (the region over the
slope of the seamount) and far-field (the region over the flat bottom of the ocean). An important distinction is that the
high vertical wavenumber near-inertial current shear is amplified only at mid-latitudes in the far-field (owing to a parametric
subharmonic instability (PSI)), whereas it is amplified both at mid-and high-latitudes (above the latitude where PSI can occur)
in the near-field. In order to clarify the generating mechanism for the strong shear in the near-field, additional numerical
experiments are carried out with the GM-like background internal waves removed. The experiments show that the strong shear
is also created, indicating that it is not caused by the interaction between the background GM-like internal waves and the
semidiurnal internal tides. One possible explanation is proposed for the amplification of high vertical wavenumber near-inertial
current shear in the near-field where tide residual flow resulting from tide-topography interaction plays an important role
in transferring energy from high-mode internal tides to near-inertial internal waves. 相似文献
14.
基于锚碇观测资料，本文分析了南海西北部陆坡区上层海洋对台风“杜苏芮”的动力学和热力学响应特征。在动力学响应方面，台风“杜苏芮”期间上层流速显著增强，混合层纬向流速可达1.20 m/s；“杜苏芮”经过后上层海水运动以近惯性振荡为主(流向顺时针旋转周期在36～40 h之间)。近惯性能量在垂向分布上存在两个高值中心，分别位于混合层和温跃层深度上。近惯性能量耗散过程的e折时间尺度约为3.7 d，我们认为能量的向下传播在局地近惯性能量衰减过程中起主要作用。对能量谱的分析表明，“杜苏芮”作用期间近惯性频率能量相对于其作用前增大了约29.4倍，而全日和半日频率(K1和M2)能量有所减弱。此外，能量谱显示近惯性频率存在明显的“蓝移”现象，即对于纬向和经向流速分量在400 m以浅平均的近惯性振荡频率分别为1.167 f0和1.170 f0(f0为局地惯性频率)。蓝移与近惯性内波的向下传播及正的相对涡度的输入有关。在热力学响应方面，上层海洋在台风的搅拌作用下，40～250 m深度均出现较小增温，最大增温幅度接近1°C；此外70 m以浅盐度的降低可能与台风过境时的降水相关，而Ekman抽吸引起的上升流则可能对70～100 m深度盐度的升高具有重要作用。 相似文献
15.
An array of three bottom-mounted ADCP moorings was deployed on the prevailing propagation path of strong internal tides for nearly 1 year across the continental slope in the northern South China Sea. These velocity measurements are used to study the intra-annual variability of diurnal and semidiurnal internal tidal energy in the region. A numerical model, the Luzon Strait Ocean Nowcast/Forecast System developed at the U.S. Naval Research Laboratory that covers the northern South China Sea and the Kuroshio, is used to interpret the observed variation of internal tidal energy on the Dongsha slope. Internal tides are generated primarily at the two submarine ridges in the Luzon Strait. At the western ridge generation site, the westward energy flux of the diurnal internal tide is sensitive to the stratification and isopycnal slope associated with the Kuroshio. The horizontal shear at the Kuroshio front does not modify the propagation path of either diurnal or semidiurnal tides because the relative vorticity of the Kuroshio in Luzon Strait is not strong enough to increase the effective inertial frequency to the intrinsic frequency of the internal tides. The variation of internal tidal energy on the continental slope and Dongsha plateau can be attributed to the variation in tidal beam propagation in the northern South China Sea. 相似文献
16.
《Deep Sea Research Part I: Oceanographic Research Papers》2007,54(4):533-556
ADCP measurements of the velocity structure in the permanent thermocline at two locations over the continental slope in the Bay of Biscay are presented. The vertical variation of the contribution of the inertia-gravity waveband to the kinetic energy, vertical motion, and current shear are analysed. The semi-diurnal tides together with near-inertial waves appear to provide over 70% of the high-frequency kinetic energy (>1/3 cpd). Over the vertical range of the ADCP observations the phase of the harmonic M2 tide changes up to 155°, while the kinetic energy varies in the vertical by a factor of 3.8, showing the importance of the contribution of internal waves to the observed tidal motion. Both semi-diurnal internal tidal waves and near-inertial waves have a vertically restricted distribution of the variance of the horizontal and vertical velocity, as in internal wave beams. The short-term 14-day averaged amplitude and phase lag of the M2 tide shows large temporal changes, with a characteristic 40–45 day time scale. These changes are probably related to variations in generation sites and propagation paths of the internal tide, because of changes in the temperature and salinity stratification due to the presence of meso-scale eddies. The relatively large shear in the inertia-gravity wave band, mainly at near-inertial frequencies, supports low-gradient Richardson numbers that are well below 1 for nearly half of the time. This implies that the large shear may support turbulent mixing for a large part of the time. 相似文献
17.
本文使用吕宋海峡以东的潜标观测的长达1年的海流数据,重点对该海域海流的高频波动(潮流)的垂向分布及其时间变化特征进行了分析,结果表明:该海域次表层(100～160 m)的潮动能比中层(1 550 m)和深层(2 560 m)大1～2个数量级,近底层(4 040 m)的潮动能略大于中、深层;次表层为不正规半日潮流,中、深层为不正规全日潮流;各层次潮动能均在夏季(6?9月)和冬季(2?3月)增强,与M2分潮和K1分潮在夏季和冬季的增强相对应;各层次海流的高频波动以顺时针旋转为主,次表层海流近惯性周期接近当地理论惯性周期,中、深层略小于当地理论惯性周期。 相似文献
18.
南海北部2011年台风“纳沙”尾迹处近惯性内波特征的研究 总被引：5，自引：0，他引：5
In September 2011, Typhoon Nesat passed over a moored array of instruments recording current and temperature in the northern South China Sea（SCS）. A wake of baroclinic near-inertial waves（NIWs） commenced after Nesat passed the array. The associated near-inertial currents are surface-intensified and clockwise-polarized. The vertical range of NIWs reached 300 m, where the vertical range is defined as the maximum depth of the horizontal near-inertial velocity 5 cm/s. The current oscillations have a frequency of 0.709 9 cycles per day（cpd）, which is 0.025 f higher than the local inertial frequency. The NIWs have an e-folding time-scale of 10 d based on the evolution of the near-inertial kinetic energy. The depth-leading phase of near-inertial currents indicates downward group velocity and energy flux. The estimated vertical phase velocity and group velocity are 0.27 and 0.08 cm/s respectively, corresponding to a vertical wavelength of 329 m. A spectral analysis reveals that NIWs act as a crucial process to redistribute the energy injected by Typhoon Nesat. A normal mode and an empirical orthogonal function analysis indicate that the second mode has a dominant variance contribution of 81%, and the corresponding horizontal phase velocity and wavelength are 3.50 m/s and 420 km respectively. The remarkable large horizontal phase velocity is relevant to the rotation of the earth, and a quantitative analysis suggests that the phase velocity of the NIWs with a blue-shift of 0.025 f overwhelms that of internal gravity waves by a factor of 4.6. 相似文献
19.
继第部分之后研究了惯性内波和近惯性内波由f～的作用所致的剪切不稳定引起的破碎机制。物理上,该机制很象存在由风应力所致薄表面涡旋漂流层时表面波的破碎与饱和过程。惯性内波和近惯性内波的破碎产物与小尺度湍流一起形成了混合块,它与Gregg等人(1986)的持久混合观测结果一致。依据Thorpe(1973)实验的结果作者提出了一个估计湍流动能耗散率和消衰时间的方法。结果表明,在剪切不稳定中近惯性内波在湍动耗散中起了关键作用,而惯性内波引起非常弱的湍动耗散。使用内波能量谱的标准总能量密度估计出的近惯性内波的耗散率和消衰时间与PATCHEX测量结果非常一致。文中还讨论了几个与此破碎机制有关的问题。 相似文献
20.
Is the small-scale turbulence an exclusive breaking product of oceanic internal waves 总被引：1，自引：1，他引：0
FAN Zhisong 《海洋学报(英文版)》2011,30(6):1-11
On the basis of the theoretical research results by the author and the literature published up to date, the analysis and the justification presented in this paper show that the breaking products of oceanic internal waves are not only turbulence, but also the fine-scale near-inertial internal waves (the oceanic reversible finestructure) for inertial waves and the internal solitary waves for internal tides respectively. It was found that the oceanic reversible finestructure may be induced by the effect of the horizontal component f (f = 2Ωcosφ) of the rotation vector on inertial waves. And a new instability of the theoretical shear and strain spectra due to the effect of f occurs at critical vertical wavenumber β c ≈ 0.1 cpm. It happens when the levels of shear and strain of the reversible finestructure are higher than those of inertial waves, which is induced by the effect of f along an "iso-potential-pycnal" of internal wave. If all breaking products of internal waves are taken into account, the average kinetic energy dissipation rate is an order of magnitude larger than the values of turbulence observed by microstructure measurements. The author’s theoretical research results are basically in agreement with those observed in IWEX, DRIFTER and PATCHEX experiments. An important impersonal fact is that on the mean temporal scale of thermohaline circulation these breaking products of internal waves exist simultaneously with turbulence. Because inertial waves are generated by winds at the surface, and internal tides are generated by strong tide-topography interactions, the analysis and justification in this paper support in principle the abyssal recipes Ⅱ:energetics of tidal and wind mixing by Munk & Wunsch in 1998, in despite of the results of microstructure measurements for the turbulent kinetic energy dissipation rate and the diapycnal turbulent eddy diffusivity. 相似文献