Seasonal characteristics of internal tides and their responses to background currents in the Luzon Strait
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摘要: 基于2008年秋季至2009年夏季共9个月的锚定潜标流速资料,分析了吕宋海峡西南內潮的时空特征.谱分析结果显示,该观测点全日內潮和半日內潮较为显著,尤其体现在顺时针旋转部分.除春季第二模态占优外,全日內潮主在其余三个季节均以第一模态为主,而半日內潮呈现变化的多模态结构.此外,全日內潮的动能具有明显的季节差异,冬季能量最强,夏季紧随其后,而在春、秋两季能量最小.通过分析发现,非相干运动对此季节性特征起主要作用,它反映了內潮与背景场的相互作用.然而,半日內潮却没有显著的季节性差异,而且能量较全日內潮更小,尤其在冬季,只有全日內潮动能的三分之一.同时,半日內潮的不规则变化也是与多变的背景场相关的.半日內潮的非相干部分占到了半日內潮总能量的37%左右,而全日內潮更小一些,只有22.2%.Abstract: The spatial-temporal characteristics of internal tides (ITs) in the southwest Luzon Strait are examined, based on 9-month mooring current records from autumn 2008 to summer 2009. The results of spectral analysis show that the ITs in diurnal and semidiurnal frequencies are prominent at the mooring site, especially for the clockwise rotary component. The diurnal ITs are mostly dominated by the first mode except for that in spring when the second mode is relatively predominant. The semidiurnal ITs display a variable multimodal structure. Moreover, an apparent difference is detected in the kinetic energy of diurnal ITs. The energy is strongest in winter, and followed by that in summer, whereas the value is smallest in spring and autumn. It is suggested that the incoherent motions are responsible for the significant seasonal variations of diurnal ITs, reflecting interaction between diurnal ITs and the varying background conditions. However, the semidiurnal ITs are independent of seasonal change, whose energy is smaller and only one-third of the diurnal energy in winter. Nevertheless, the abnormal variations of semidiurnal ITs are also related to the variable background conditions. The incoherent semidiurnal constituent accounts for about 37% of the total semidiurnal tidal kinetic energy, but the diurnal tidal motions contain fewer incoherent component (22.2%).
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Key words:
- internal tide /
- seasonal variation /
- background current /
- Luzon Strait
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Alford M H, MacKinnon J A, Nash J D, et al. 2011. Energy flux and dis-sipation in Luzon Strait: two tales of two ridges. Journal of Phys-ical Oceanography, 41(11): 2211-2222 Buijsman M C, Kanarska Y, McWilliams J C. 2010a. On the genera-tion and evolution of nonlinear internal waves in the South China Sea. Journal of Geophysical Research, 115: C02012 Buijsman M C, McWilliams J C, Jackson C R. 2010b. East-west asym-metry in nonlinear internal waves from Luzon Strait. Journal of Geophysical Research, 115: C10057 Caruso M J, Gawarkiewicz G G, Beardsley R C. 2006. Interannual vari-ability of the Kuroshio intrusion in the South China Sea. Journ-al of Oceanography, 62(4): 559-575 Chavanne C, Flament P, Carter M, et al. 2010. The surface expression of semidiurnal internal tides near a strong source at Hawaii. Part I: observations and numerical predictions. Journal of Phys-ical Oceanography, 40(6): 1155-1179 Chao S Y, Ko D S, Lien R C, et al. 2007. Assessing the west ridge of Luzon Strait as an internal wave mediator. Journal of Oceano-graphy, 63(6): 897-911 Chen Gengxin, Gan Jianping, Xie Qiang, et al. 2012. Eddy heat and salt transports in the South China Sea and their seasonal modu-lations. Journal of Geophysical Research, 117: C05021 Chen Gengxin, Hu Po, Hou Yijun, et al. 2011. Intrusion of the Kurosh-io into the South China Sea, in September 2008. Journal of Oceanography, 67(4): 439-448 Chu P C, Li Rongfeng. 2000. South China Sea isopycnal-surface circu-lation. Journal of Physical Oceanography, 30(9): 2419-2438 Chu Xiaoqing, Xue Huijie, Qi Yiquan, et al. 2014. An exceptional anti-cyclonic eddy in the South China Sea in 2010. Journal of Geo-physical Research, 119(2): 881-897 Du Tao, Tseng Y H, Yan Xiaohai. 2008. Impacts of tidal currents and Kuroshio intrusion on the generation of nonlinear internal waves in Luzon Strait. Journal of Geophysical Research, 113: C08015 Duda T F, Lynch J F, Irish J D, et al. 2004. Internal tide and nonlinear internal wave behavior at the continental slope in the northern South China Sea. IEEE Journal of Oceanic Engineering, 29(4): 1105-1130 Eich M L, Merrifield M A, Alford M H. 2004. Structure and variability of semidiurnal internal tides in Mamala Bay, Hawaii. Journal of Geophysical Research, 109: C05010 Gerkema, T, Lam F P A, Maas L R M. 2004. Internal tides in the Bay of Biscay: Conversion rates and seasonal effects. Deep-Sea Re-search Part II: Topical Studies in Oceanography, 51(25-26): 2995-3008 Holloway P E, Merrifield M A. 1999. Internal tide generation by seamounts, ridges, and islands. Journal of Geophysical Re-search, 104(C11): 25937-25951 Hu Jianyu, Kawamura H, Hong Huasheng, et al. 2000. A review on the currents in the South China Sea: seasonal circulation, South China Sea warm current and Kuroshio intrusion. Journal of Oceanography, 56(6): 607-624 Huan Lee I, Wang Yuhuai, Yang Y, et al. 2012. Temporal variability of internal tides in the northeast South China Sea. Journal of Geo-physical Research, 117: C02013 Jan S, Chern C S, Wang J, et al. 2012. Generation and propagation of baroclinic tides modified by the Kuroshio in the Luzon Strait. Journal of Geophysical Research, 117: C02019 Jan S, Lien R C, Ting Chihua. 2008. Numerical study of baroclinic tides in Luzon Strait. Journal of Oceanography, 64(5): 789-802 Katsumata K, Wijffels S E, Steinberg C R, et al. 2010. Variability of the semidiurnal internal tides observed on the Timor Shelf. Journ-al of Geophysical Research, 115: C10008 Liao Guanghong, Yuan Yaochu, Arata K, et al. 2011. Analysis of in-ternal tidal characteristics in the layer above 450 m from acous-tic Doppler current profiler observations in the Luzon Strait. Science China Earth Science, 54(7): 1078-1094 Liao Guanghong, Yuan Yaochu, Yang Chenghao, et al. 2012. Current observations of internal tides and parametric subharmonic in-stability in Luzon Strait. Atmosphere-Ocean, 50(1): 59-76 Munk W H. 1981. Internal Waves and Small-scale Processes. In: War-ren B A, Wunsch C, eds. Evolution of Physical Oceanography. Cambridge: MIT Press, 264-291 Nash J D, Kelly S M, Shroyer E L, et al. 2012a. The unpredictable nature of internal tides on continental shelves. Journal of Phys-ical Oceanography, 42(11): 1981-2000 Nash J D, Shroyer E L, Kelly S M, et al. 2012b. Are any coastal internal tides predictable?. Oceanography, 25(2): 80-95 Niwa Y, Hibiya T. 2001. Numerical study of the spatial distribution of the M2 internal tides in the Pacific Ocean. Journal of Geophys-ical Research, 106(C10): 22441-22449 Niwa Y, Hibiya T. 2004. Three-dimensional numerical simulation of M2 internal tides in the East China Sea. Journal of Geophysical Research, 109: C04027 Nan Feng, Xue Huijie, Chai Fei, et al. 2011. Identification of different types of Kuroshio intrusion into the South China Sea. Ocean Dynamics, 61(9): 1291-1304 Park J-H, Farmer D. Effects of Kuroshio intrusions on nonlinear in-ternal waves in the South China Sea during winter. Journal of Geophysical Research, 118: 7081-7094 Pawlowicz R, Beardsley B, Lentz S. 2002. Classical tidal harmonic analysis including error estimates in MATLAB using T_TIDE. Computers & Geosciences, 28(8): 929-937 Qu Tangdong, Kim Y Y, Yaremchuk M, et al. 2004. Can Luzon strait transport play a role in conveying the impact of ENSO to the South China Sea?. Journal of Climate, 17(18): 3644-3657 Rainville L, Pinkel R. 2006. Propagation of low-mode internal waves through the ocean. Journal of Physical Oceanography, 36(6): 1220-1236 Ramp S R, Tang T Y, Duda T F, et al. 2004. Internal solitons in the northeastern South China Sea, part I: Sources and deep water propagation. IEEE Journal of Oceanic Engineering, 29(4): 1157-1181 Shaw P T, Ko D S, Chao S Y. 2009. Internal solitary waves induced by flow over a ridge: With applications to the northern South China Sea. Journal of Geophysical Research, 114: C02019 Shaun Johnston T M, Rudnick D L, Aflord M H, et al. 2013. Internal tidal energy fluxes in the South China Sea from density and ve-locity measurements by gliders. Journal of Geophysical Re-search, 118(8): 3939-3949 Simmons H L, Chang M H, Chang Y T, et al. 2011. Modeling and pre-diction of internal waves in the South China Sea. Oceano-graphy, 24(4): 88-99 Simmons H L, Hallberg R W, Arbic B K. 2004. Internal wave genera-tion in a global baroclinic tide model. Deep-Sea Research Part II: Topical Studies in Oceanography, 51(25-26): 3043-3068 Tian Jiwei, Yang Qingxuan, Liang Xinfeng, et al. 2006. Observation of Luzon Strait transport. Geophysical Research Letters, 33(19): L19607 Thorpe S A. 1978. On the shape and breaking of finite amplitude in-ternal gravity waves in a shear flows. Journal of Fluid Mechan-ics, 85(1): 7-31 van Haren H. 2004. Incoherent internal tidal currents in the deep ocean. Ocean Dynamics, 54(1): 66-76 Xie Lingling. 2009. Study on the circulation in western Northern Pacific and the water exchange between the Pacific and the South China Sea [dissertation]. Qingdao: Ocean University of China Xu Zhenhua, Yin Baoshu, Hou Yijun, et al. 2013. Variability of intern-al tides and near-inertial waves on the continental slope of the northwestern South China Sea. Journal of Geophysical Re-search, 118(1): 197-211 Yuan Yeli, Zheng Quanan, Dai Dejun, et al. 2006. Mechanism of in-ternal waves in the Luzon Strait. Journal of Geophysical Re-search, 111: C11S17 Zhang Z, Fringer O B, Ramp S R. 2011. Three-dimensional, nonhyd-rostatic numerical simulation of nonlinear internal wave gener-ation and propagation in the South China Sea. Journal of Geo-physical Research, 116: C05022 Zheng Quanan, Susanto R W, Ho C R, et al. 2007. Statistical and dy-namical analyses of generation mechanisms of solitary internal waves in the northern South China Sea. Journal of Geophysical Research, 112: C03021
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