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1.
Tides are believed to drive vertical mixing in the Arctic Ocean, thereby helping heat to reach the bottom of the sea ice layer, especially in regions with thick ice covers. However, tides are usually not included in ocean models. We investigated the effect of tides on sea ice in the Arctic Ocean using an ice-coupled ocean model that includes tides simultaneously. We found that with tidal forcing, the volume of sea ice increased by 8.5% in Baffin Bay, whereas it decreased by 17.8% in the Canadian Arctic Archipelago. The increase in sea ice volume in Baffin Bay results from the convergence of sea ice, driven by tidal residual currents. In contrast, the decrease in ice volume in the Canadian Archipelago is due to the suppression of ice formation in winter, especially in areas with steep topography, where the vertical mixing of temperature is enhanced by tides. Our results imply that tides should be directly included into the oceanic general circulation model (OGCM) to realistically reproduce the distribution of sea ice in the Arctic Ocean. 相似文献
2.
为实现多频多模GNSS浮标在远距离海洋潮汐测量中的应用,基于精密单点定位(precision pointing positioning,PPP)数据处理策略获取潮位信息,以压力验潮仪为参考,对GNSS浮标测量海面高进行经验模态分解(empirical mode decomposition,EMD),滤去高频波浪和噪声,获取潮位进行精度分析。结果表明:多系统可以提高PPP解算潮位精度。GPS/GLONASS双系统和GPS/GLONASS/Bei Dou三系统PPP提取潮位与验潮仪潮位差值的最大误差均小于18cm,RMSE小于6. 5cm。因此,多系统PPP解算GNSS浮标海面高可以实现远离海岸的潮位获取与监测,能够提高海上潮位测量的效率。 相似文献
3.
南海潮汐主要分潮振幅变化趋势研究 总被引：1，自引：1，他引：0
潮汐变化研究对于海洋工程、沿海地区洪涝灾害预防、海上交通等各个方面都有着重要的意义。由于验潮站都集中在近海,所以之前潮汐变化研究主要集中在近海海域。相比之下,深海地区由于长期高频水位观测的缺乏导致相关的潮汐变化研究非常少。基于近海验潮站数据和深海卫星高度计数据,本文首次用非平稳潮汐调和分析工具包S_TIDE提取了南海4大主要分潮(M2、S2、K1、O1)振幅的长期趋势。研究发现在南海大部分地区,4大主要分潮的振幅都是比较稳定的,不存在显著的上升趋势或下降趋势。在南海少部分地区4大主要分潮的振幅存在显著的趋势,最大的上升趋势可达2.91 mm/a,最大的下降趋势可达3.50 mm/a。该海域潮汐的长期趋势可能与内潮海表面信号的变化有关。卫星观测到的潮汐既包含正压潮,也包含内潮海表面信号。南海作为全球内潮活动最活跃的海域之一,其内潮海表面信号是非常显著的。而内潮对海洋层化的变化是非常敏感的,海洋层化的变化会影响内潮的生成、传播和耗散以及内潮在海表的显示,最终引起该海域潮汐振幅的长期趋势。 相似文献
4.
This paper discusses tidal effects on an observation scheme to determine a point at the bottom of the sea by combining GPS and Sonar observations. For the purpose, three kinds of Earth tides are introduced (i.e., the crust tide, the equipotential surface point (ocean depth) tide, and the geoid tide). The corresponding mathematical expressions are derived to demonstrate the tidal effects on GPS and Sonar observations. The relations between the Earth tides are also discussed. Theoretical results imply a very interesting conclusion, namely that, for a local area, the static position of a point at the bottom of sea can be obtained by the dynamic observations without any tidal correction. Actually, the tidal effects cancel each other in the mentioned observation scheme. It therefore indicates that the observation scheme is free of tidal effects. Furthermore, we learned that the divergence caused by any error source on ocean surface is canceled and does not affect the final results. Therefore, to determine the position of a point at the bottom of sea, we need not consider any tidal effects. 相似文献
5.
This paper discusses tidal effects on an observation scheme to determine a point at the bottom of the sea by combining GPS and Sonar observations. For the purpose, three kinds of Earth tides are introduced (i.e., the crust tide, the equipotential surface point (ocean depth) tide, and the geoid tide). The corresponding mathematical expressions are derived to demonstrate the tidal effects on GPS and Sonar observations. The relations between the Earth tides are also discussed. Theoretical results imply a very interesting conclusion, namely that, for a local area, the static position of a point at the bottom of sea can be obtained by the dynamic observations without any tidal correction. Actually, the tidal effects cancel each other in the mentioned observation scheme. It therefore indicates that the observation scheme is free of tidal effects. Furthermore, we learned that the divergence caused by any error source on ocean surface is canceled and does not affect the final results. Therefore, to determine the position of a point at the bottom of sea, we need not consider any tidal effects. 相似文献
6.
Kuo-Chuin Wong Brian Dzwonkowski William J. Ullman 《Estuarine, Coastal and Shelf Science》2009,84(4):440-446
The instantaneous sea level determined at two sites in the Murderkill Estuary, a tributary of Delaware Bay, results from the superposition of temporal variability operating over different time and spatial scales. Over the relatively short tidal time scales, the semidiurnal tides that represent the dominant tidal constituents in lower Delaware Bay show a modest increase in tidal amplitudes from the bay mouth (Lewes, Delaware), up to Bowers Beach (the mouth of the Murderkill Estuary). However, as the tides propagate into the Murderkill Estuary, the semidiurnal constituents undergo heavy attenuation, resulting in a 48% reduction in tidal amplitude from Bowers to Frederica (approximately the extent of saline intrusion). The diurnal tide, on the other hand, experiences only a 25% reduction in amplitude. The limited tidal asymmetry that is observed may be a result of interaction between flows in the tidal channel and the adjacent salt marsh. At longer time scales, the subtidal sea level experiences no attenuation. The Murderkill Estuary thus behaves like a low pass filter to preferentially damp out high frequency sea level forcing from lower Delaware Bay. The subtidal volume flux in the Murderkill is highly coherent with the time rate of change of sea level, indicating that the Murderkill basically co-oscillates with Delaware Bay in a standing wave fashion over the subtidal time scale. This remote coupling controls more than 90% of the variance in subtidal sea level in the estuary. The surface slopes in the lower bay and the Murderkill Estuary are closely correlated with winds along the orientation of the two waterways, consistent with the effect of local wind on subtidal sea level. 相似文献
7.
TOPEX/POSEIDON高度计浅海潮汐混淆的初步分析 总被引：22，自引：5，他引：17
根据对卫星轨道特征和观测结果的分析,对TOPEX/POSEIDON(简称T/P)星载高度计在我国近海的潮致混淆现象进行了初步研究.分析表明,在浅海区T/P高度计的观测结果存在很强的潮致高频混淆.NASA分发的地球物理记录中所提供的潮汐订正值虽适用于大洋,但不能有效地除去浅海潮汐.虽然如此,T/P潮致混淆的主要频段的周期小于90d,因而可以通过滤波方法提取周期较长的海面高度季节信号,从而用于季节环流(如南海季风环流)的研究.采用FFT/IFFT方法滤波试验的结果显示,T/P的海面高度观测结果有很高的精度,滤波处理后的海面高度距平变化和地面潮位观测结果一致性良好,上、下行轨道交叉处相邻测点间的标准偏差在3cm左右,可满足南海环流研究的需要. 相似文献
8.
Surface manifestation of internal tides in the deep ocean: observations from altimetry and island gauges 总被引：3，自引：0，他引：3
The sea-surface height signatures of internal tides in the deep ocean, amounting to a few centimeters or less, are studied using two complementary measurement types: satellite altimetry and island tide gauges. Altimetry can detect internal tides that maintain coherence with the astronomical forcing; island gauges can monitor temporal variability which, in some circumstances, is due to internal tides varying in response to changes in the oceanic medium. This latter mechanism is at work at Hilo and other stations on the northern coasts of the Hawaiian Islands. By detecting spatially coherent low-frequency internal-tide modulations, the tide gauges, along with inverted echo sounders at sea, suggest that the mean internal tide is also spatially coherent; satellite altimetry confirms this. At Hawaii and in many other places, Topex/Poseidon altimetry detects mean surface waves, spatially coherent and propagating great distances (> 1000 km) before decaying below background noise. When temporal variability is small, the altimetry (plus information on ocean density) sets useful constraints on energy fluxes into internal tides. At the Hawaiian Ridge, 15 GW of tidal power is being converted from barotropic to first-mode baroclinic motion. Examples elsewhere warn that a simplistic interpretation of the altimetry, without regard to variability, noise, or in situ information, may be highly misleading. With such uncertainties, extension of the Hawaiian results into a usefully realistic estimate of the global internal-tide energy balance appears premature at this time. 相似文献
9.
三门湾外海的潮汐和潮流特征 总被引：1，自引：0，他引：1
针对2009年5月-7月三门湾外海D8和D9两个站位布放的防渔网底拖锚系ADCP连续观测获取的流速资料和水位资料,采用调和分析和功率谱分析等研究方法,分析了该海域的潮汐和潮流特征,结果显示:该海域潮汐类型为正规半日潮,近岸的D9站浅水分潮比离岸的D8站显著,潮汐呈现出回归潮特征。三门湾外海潮流半日分潮能量最大, 各层潮流呈现出旋转流性质;椭圆率随水深增加;M2、K1分潮流最大流速均在次表层最大;最大分潮流速发生时刻底层比中、上层提前约半小时;该海域潮流的半日分潮流以正压为主,全日分潮流则表现出较为明显的斜压性。 相似文献
10.
内潮耗散与自吸-负荷潮对南海潮波影响的数值研究 总被引：1，自引：0，他引：1
利用非结构三角形网格的FVCOM海洋数值模式,在其传统二维潮波方程中加入参数化的内潮耗散项和自吸-负荷潮项,计算了南海及其周边海域的M_2、S_2、K_1和O_1分潮的分布。与实测值的比较表明,引入这两项对模拟准确度的提高有明显效果。根据模式结果本文计算分析了研究海域的潮能输入和耗散。能量输入计算表明,能通量是潮能输入的最主要构成部分,通过吕宋海峡断面进入南海的M_2和K_1分潮能通量分别为38和29GW;半日周期的自吸-负荷潮能量输入以负值居多,而全日周期的自吸-负荷潮能量输入以正值居多,因而自吸-负荷潮减弱了南海的半日潮,并加强了南海的全日潮。引潮力的作用也减弱了半日潮而加强了全日潮,但其作用要小于自吸-负荷潮。潮能耗散的分析显示底摩擦耗散在沿岸浅水区域起主导作用,内潮耗散则主要发生在深水区域。内潮耗散的最大值出现在吕宋海峡,且位于南海之外的海峡东部的耗散量大于位于南海之内的海峡西部的耗散量。对M_2和K_1分潮吕宋海峡的内潮耗散总值分别达到16和23GW。 相似文献
11.
This article describes an “absolute” calibration of Jason-1 (J-1) altimeter sea surface height bias using a method developed for TOPEX/Poseidon (T/P) bias determination reported previously. The method makes use of U.K. tide gauges equipped with Global Positioning System (GPS) receivers to measure sea surface heights at the same time, and in the same geocentric reference frame, as Jason-1 altimetric heights recorded in the nearby ocean. The main time-dependent components of the observed altimeter-minus-gauge height-difference time series are due to the slightly different ocean tides at the gauge and in the ocean. The main harmonic coefficients of the tide differences are calculated from analysis of the copious TOPEX data set and then applied to the determination of T, P, and J-1 bias in turn. Datum connections between the tide gauge and altimetric sea surface heights are made by means of precise, local geoid differences from the EGG97 model. By these means, we have estimated Jason-1 altimeter bias determined from Geophysical Data Record (GDR) data for cycles 1–61 to be 12.9 cm, with an accuracy estimated to be approximately 3 cm on the basis of our earlier work. This J-1 bias value is in close agreement with those determined by other groups, which provides a further confirmation of the validity of our method and of its potential for application in other parts of the world where suitable tide gauge, GPS, and geoid information exist. 相似文献
12.
《Ocean Modelling》2010,33(3-4):175-187
This paper presents a five-year global simulation of HYCOM, the HYbrid Coordinate Ocean Model, that simultaneously resolves the eddying general circulation, barotropic tides, and baroclinic tides with 32 layers in the vertical direction and 1/12.5° (equatorial) horizontal grid spacing. A parameterized topographic wave drag is inserted into the model and tuned so that the surface tidal elevations are of comparable accuracy to those in optimally tuned forward tide models used in previous studies. The model captures 93% of the open-ocean sea-surface height variance of the eight largest tidal constituents, as recorded by a standard set of 102 pelagic tide gauges spread around the World Ocean. In order to minimize the impact of the wave drag on non-tidal motions, the model utilizes a running 25-h average to approximately separate tidal and non-tidal components of the near-bottom flow. In contrast to earlier high-resolution global baroclinic tide simulations, which utilized tidal forcing only, the simulation presented here has a horizontally non-uniform stratification, supported by the wind- and buoyancy forcing. The horizontally varying stratification affects the baroclinic tides in high latitudes to first order. The magnitude of the internal tide perturbations to sea surface elevation amplitude and phase in a large box surrounding Hawai’i is quite similar to that observed in satellite altimeter data, although the exact locations of peaks and troughs in the modeled perturbations differ from those in the observed perturbations. 相似文献
13.
The HY-2A satellite, which is equipped with a radar altimeter and was launched on August 16, 2011, is the first Chinese marine dynamic environmental monitoring satellite. Extracting ocean tides is one of the important applications of the radar altimeter data. The radar altimeter data of the HY-2A satellite from November 1, 2011 to August 16, 2014 are used herein to extract global ocean tides. The constants representing the tidal constituents are extracted by HY-2A RA data with harmonic analysis ... 相似文献
14.
The published global ocean tide models show good agreement in deep oceans and exhibit differences in complex coastal areas, along with subsequent Ocean Tide Loading Displacement (OTLD) modeling differences. Meanwhile, OTLD parameters (amplitudes and phase lags) derived by Global Positioning System (GPS) Precise Point Positioning (PPP) approach need long time to converge to a stable state and show poor precision of S2, K1, and K2 constituents. Based on the fact that no constraint is imposed in the current kinematic solution, a new method is put forward, in which global ocean tide model predictions are taken as the priori information constraints to speed up the convergence rate and improve the accuracy of the GPS-derived OTLD parameters. First, the data of tide gauge from 01 January 2014 to 31 December 2016 are used to generate the harmonic parameters to evaluate the accuracy of six global ocean tide models and a regional ocean tide model (osu.chinesea.2010). Osu.chinesea.2010 model shows good agreement with the tide gauge results, while NAO99b model presents relatively large difference. The predictions from osu.chinesea.2010 and NAO99b model are employed as reference and the prior information, respectively. Second, continuous observations of 12 GPS sites during 2006–2013 in Hong Kong are collected to generate three dimensional OTLD amplitudes and phase lags of eight constituents using PPP with prior information constraints approach and harmonic analysis. Third, comparing the convergence time of eight constituents from PPP without and with priori information constraints approaches, the results show that the new method can significantly improve the convergence rate of OTLD amplitude estimates which obtain a certain level of stability seven years earlier than that derived by the PPP without priori information constraints. Precision of OTLD parameters derived by the new method is about 1 mm. By comparing with the precision of single PPP approach, the accuracy of eight constituents has been improved, especially for S2, K1, and K2 constituents. Finally, through comparing the different correction effects of OTLD estimates on the coordinates and their time series of the ground GPS stations, the results show that OTLD estimates derived by the new approach have similar influence as the osu.chinasea.2010 ocean tide model. The new method provides an effective means to improve the convergence and precision of the GPS-derived OTLD parameters, and achieve a similar correction as the high precision ocean tide model. 相似文献
15.
This article describes an “absolute” calibration of Jason-1 (J-1) altimeter sea surface height bias using a method developed for TOPEX/Poseidon (T/P) bias determination reported previously. The method makes use of U.K. tide gauges equipped with Global Positioning System (GPS) receivers to measure sea surface heights at the same time, and in the same geocentric reference frame, as Jason-1 altimetric heights recorded in the nearby ocean. The main time-dependent components of the observed altimeter-minus-gauge height-difference time series are due to the slightly different ocean tides at the gauge and in the ocean. The main harmonic coefficients of the tide differences are calculated from analysis of the copious TOPEX data set and then applied to the determination of T, P, and J-1 bias in turn. Datum connections between the tide gauge and altimetric sea surface heights are made by means of precise, local geoid differences from the EGG97 model. By these means, we have estimated Jason-1 altimeter bias determined from Geophysical Data Record (GDR) data for cycles 1-61 to be 12.9 cm, with an accuracy estimated to be approximately 3 cm on the basis of our earlier work. This J-1 bias value is in close agreement with those determined by other groups, which provides a further confirmation of the validity of our method and of its potential for application in other parts of the world where suitable tide gauge, GPS, and geoid information exist. 相似文献
16.
T. J. P. Gwilliam 《Ocean Engineering》1976,3(6):391-401
With ever increasing information being collected by the offshore continental shelf tide gauges, it became inevitable that researches into ocean tides would require instrumentation to collect tidal data in the deep oceans.This paper briefly describes the temperature and pressure sensors developed, and used by the Institute of Oceanographic Sciences (Wormley), in response to this requirement. Also described are the techniques and equipment used to calibrate these sensors.The deep sea tide gauges, each of which include two pressure and one temperature sensor, have now been operationally deployed on four occasions at pressures up to 300 bars (3000 m) providing well over 100 days of tidal data. In an international exercise to evaluate the performance of existing deep sea pressure sensors, results show that the unit described in this paper compares favourably with the other sensors. For example, the amplitude of the semi-diurnal components were within 1% of the average value, determined by all the sensors. The temperature sensor has an operational range within the limits — 1° and + 40°C and exhibiting a stability of the order 8 milli°C/month. 相似文献
17.
18.
Long-term hourly data from 35 tide gauge stations, including 15 stations in the Gulf of Finland, were used to examine tidal sea level oscillations of the Baltic Sea. High-resolution spectral analysis revealed the well-defined fine structure of tidal peaks with diurnal peaks at most stations being higher than semidiurnal. At some stations (e.g., Narva, Daugava, and Wladyslawowo), high frequency radiational tidal peaks with periods multiple of the solar day (3, 4, 5, 6, and 8 cpd) were detected; the respective oscillations are supposed to be caused by seabreeze winds. Harmonic analysis of tides for individual yearly sea level series followed by vector averaging over the entire observational period was used to estimate the amplitudes and phases of 16 tidal constituents. The maximum tidal oscillations of 17–19 cm were found to be observed in the Gulf of Finland and, first of all, in Neva Bay (in the head of the gulf). Diurnal or mixed diurnal tides are predominant in almost the entire Baltic Sea. The comparison of the observed tides with those theoretically computed showed that the existing numerical models of the main tidal harmonics generally quite accurately reproduce the structure of the tides in the Baltic Sea except for some regions of the Gulf of Bothnia. 相似文献
19.
A tide circulation model of the Atlantic coast of the Iberian Peninsula has been constructed. This regional numerical model covers the whole continental shelf. The finite element computational grid is made of some 16,300 triangular elements with sizes ranging between 13 km (on the offshore boundary) and 1 km (near the coast), with local refinements on the continental shelf and in the area of Figueira da Foz. This site was selected as experimental site for the study of waves and currents in the frame of the MAST2/WAVEMOD research project.Boundary conditions along the three oceanic limits of this widely open domain are obtained from the North-Atlantic component of a World Ocean tidal numerical model known as FES94 [Le Provost, C., Genco, M.L., Lyard, F., Vincent, P. and Canceil, P. (1994) Spectroscopy of the world ocean tides from a finite element hydrodynamic model, Journal of Geophysical Research, Topex-Poseidon Special Issue]. A new radiation-like boundary condition has been introduced in the modelling system used (Telemac-2D), which solves the Shallow Water Equations (SWE), in order to interface the two models and to allow for the tidal wave to leave the northern limit without reflection. Model calibration has been performed on the dominating M2 constituent. The introduction of the astral static potential generating the tide in the SWE improved this regional model.A long duration run (1 month) has been performed, the model being forced by the eight major tide constituents. Harmonic analysis of results has been performed on 17 tide constituents, due to non-linear interactions of constituents on the continental shelf. Comparisons with the FES94 model on one hand, and with a set of coastal tide gauges on the other hand, are good. A database of tidal harmonics is now available for forecasting sea levels and currents in this area.This work has shown that diurnal shelf trapped tide waves exist in some places along the Portuguese continental shelf, which induce diurnal dominant tidal currents in these places (North of Figueira da Foz). 相似文献