Application of inversion to global ocean tide mapping

1996 ◽  
pp. 239-246 ◽  
Author(s):  
Ole B. Andersen
Keyword(s):  
Global Ocean ◽  
Ocean Tide

Tidal dissipation in the oceans: astronomical, geophysical and oceanographic consequences

1977 ◽  
Vol 287 (1347) ◽  
pp. 545-594 ◽  
Keyword(s):  
Energy Dissipation ◽  
Solid Earth ◽  
Global Ocean ◽  
Ocean Tide ◽  
The Moon ◽  
Tidal Dissipation ◽  
Tidal Forces ◽  
Degree Harmonic ◽  
Tidal Acceleration ◽  
Second Degree

The most precise way of estimating the dissipation of tidal energy in the oceans is by evaluating the rate at which work is done by the tidal forces and this quantity is completely described by the fundamental harmonic in the ocean tide expansion that has the same degree and order as the forcing function. The contribution of all other harmonics to the work integral must vanish. These harmonics have been estimated for the principal M 2 tide using several available numerical models and despite the often significant difference in the detail of the models, in the treatment of the boundary conditions and in the way dissipating forces are introduced, the results for the rate at which energy is dissipated are in good agreement. Equivalent phase lags, representing the global ocean-solid Earth response to the tidal forces and the rates of energy dissipation have been computed for other tidal frequencies, including the atmospheric tide, by using available tide models, age of tide observations and equilibrium theory. Orbits of close Earth satellites are periodically perturbed by the combined solid Earth and ocean tide and the delay of these perturbations compared with the tide potential defines the same terms as enter into the tidal dissipation problem. They provide, therefore, an independent estimate of dissipation. The results agree with the tide calculations and with the astronomical estimates. The satellite results are independent of dissipation in the Moon and a comparison of astronomical, satellite and tidal estimates of dissipation permits a separation of energy sinks in the solid Earth, the Moon and in the oceans. A precise separation is not yet possible since dissipation in the oceans dominates the other two sinks: dissipation occurs almost exclusively in the oceans and neither the solid Earth nor the Moon are important energy sinks. Lower limits to the Q of the solid Earth can be estimated by comparing the satellite results with the ocean calculations and by comparing the astronomical results with the latter. They result in Q > 120. The lunar acceleration n , the Earth’s tidal acceleration O T and the total rate of energy dissipation E estimated by the three methods give astronomical based estimate —1.36 —28±3 —7.2 ± 0.7 4.1±0.4 satellite based estimate —1.03 —24 ±5 — 6.4 ± 1.5 3.6±0.8 numerical tide model — 1.49 —30 ±3 —7.5± 0.8 4.5±0.5 The mean value for O T corresponds to an increase in the length of day of 2.7 ms cy -1 . The non-tidal acceleration of the Earth is (1.8 ± 1.0) 10 -22 s ~2 , resulting in a decrease in the length of day of 0.7 ± 0.4 ms cy -1 and is barely significant. This quantity remains the most unsatisfactory of the accelerations. The nature of the dissipating mechanism remains unclear but whatever it is it must also control the phase of the second degree harmonic in the ocean expansion. It is this harmonic that permits the transfer of angular momentum from the Earth to the Moon but the energy dissipation occurs at frequencies at the other end of the tide’s spatial spectrum. The efficacity of the break-up of the second degree term into the higher modes governs the amount of energy that is eventually dissipated. It appears that the break-up is controlled by global ocean characteristics such as the ocean­-continent geometry and sea floor topography. Friction in a few shallow seas does not appear to be as important as previously thought: New estimates for dissipation in the Bering Sea being almost an order of magnitude smaller than earlier estimates. If bottom friction is important then it must be more uniformly distributed over the world's continental shelves. Likewise, if turbulence provides an important dissipation mechanism it must be fairly uniformly distributed along, for example, coastlines or along continental margins. Such a global distribution of the dissipation makes it improbable that there has been a change in the rate of dissipation during the last few millennium as there is no evidence of changes in ocean volume, or ocean geometry or sea level beyond a few metres. It also suggests that the time scale problem can be resolved if past ocean-continent geometries led to a less efficient breakdown of the second degree harmonic into higher degree harmonics.

scholarly journals Evaluation of global ocean tide models based on tidal gravity observations in China

2020 ◽  
Author(s):  
Hongbo Tan ◽  
Chongyong Shen ◽  
Guiju Wu
Keyword(s):  
High Precision ◽  
Earth Tide ◽  
Global Ocean ◽  
Ocean Tide ◽  
Ocean Tides ◽  
Ocean Tide Model ◽  
Tidal Forces ◽  
The Earth ◽  
Gravity Observation ◽  
Ocean Tide Models

<p>Solid Earth is affected by tidal cycles triggered by the gravity attraction of the celestial bodies. However, about 70% the Earth is covered with seawater which is also affected by the tidal forces. In the coastal areas, the ocean tide loading (OTL) can reach up to 10% of the earth tide, 90% for tilt, and 25% for strain (Farrell, 1972). Since 2007, a high-precision continuous gravity observation network in China has been established with 78 stations. The long-term high-precision tidal data of the network can be used to validate, verifying and even improve the ocean tide model (OTM).</p><p>In this paper, tidal parameters of each station were extracted using the harmonic analysis method after a careful editing of the data. 8 OTMs were used for calculating the OTL. The results show that the Root-Mean-Square of the tidal residuals (M<sub>0</sub>) vary between 0.078-1.77 μgal, and the average errors as function of the distance from the sea for near(0-60km), middle(60-1000km) and far(>1000km) stations are 0.76, 0.30 and 0.21 μgal. The total final gravity residuals (Tx) of the 8 major constituents (M<sub>2</sub>, S<sub>2</sub>, N<sub>2</sub>, K<sub>2</sub>, K<sub>1</sub>, O<sub>1</sub>, P<sub>1</sub>, Q<sub>1</sub>) for the best OTM has amplitude ranging from 0.14 to 3.45 μgal. The average efficiency for O<sub>1</sub> is 77.0%, while 73.1%, 59.6% and 62.6% for K<sub>1</sub>, M<sub>2</sub> and Tx. FES2014b provides the best corrections for O<sub>1</sub> at 12 stations, while SCHW provides the best for K<sub>1 </sub><sub>,</sub>M<sub>2</sub>and Tx at 12,8and 9 stations. For the 11 costal stations, there is not an obvious best OTM. The models of DTU10, EOT11a and TPXO8 look a litter better than FES2014b, HAMTIDE and SCHW. For the 17 middle distance stations, SCHW is the best OTM obviously. For the 7 far distance stations, FES2014b and SCHW model are the best models. But the correction efficiency is worse than the near and middle stations’.</p><p>The outcome is mixed: none of the recent OTMs performs the best for all tidal waves at all stations. Surprisingly, the Schwiderski’s model although is 40 years old with a coarse resolution of 1° x 1° is performing relative well with respect to the more recent OTM. Similar results are obtained in Southeast Asia (Francis and van Dam, 2014). It could be due to systematic errors in the surroundings seas affecting all the ocean tides models. It's difficult to detect, but invert the gravity attraction and loading effect to map the ocean tides in the vicinity of China would be one way.</p>

A harmonic approach to global ocean tide analysis based on TOPEX/Poseidon satellite

2007 ◽  
Vol 28 (3) ◽  
pp. 235-255 ◽  
Author(s):  
Alireza Azmoudeh Ardalan ◽  
Hassan Hashemi-Farahani
Keyword(s):  
Global Ocean ◽  
Ocean Tide

An Assessment of Global Ocean Barotropic Tide Models Using Geodetic Mission Altimetry and Surface Drifters

2021 ◽  
Vol 51 (1) ◽  
pp. 63-82
Author(s):  
Edward D. Zaron ◽  
Shane Elipot
Keyword(s):  
Shallow Water ◽  
Deep Water ◽  
Variance Reduction ◽  
Model Performance ◽  
Data Sources ◽  
Global Ocean ◽  
Ocean Tide ◽  
Analysis Model ◽  
Surface Drifters ◽  
Ocean Tide Models

AbstractThe accuracy of three data-constrained barotropic ocean tide models is assessed by comparison with data from geodetic mission altimetry and ocean surface drifters, data sources chosen for their independence from the observational data used to develop the tide models. Because these data sources do not provide conventional time series at single locations suitable for harmonic analysis, model performance is evaluated using variance reduction statistics. The results distinguish between shallow and deep-water evaluations of the GOT410, TPXO9A, and FES2014 models; however, a hallmark of the comparisons is strong geographic variability that is not well summarized by global performance statistics. The models exhibit significant regionally coherent differences in performance that should be considered when choosing a model for a particular application. Quantitatively, the differences in explained SSH variance between the models in shallow water are only 1%–2% of the root-mean-square (RMS) tidal signal of about 50 cm, but the differences are larger at high latitudes, more than 10% of 30-cm RMS. Differences with respect to tidal currents variance are strongly influenced by small scales in shallow water and are not well represented by global averages; therefore, maps of model differences are provided. In deep water, the performance of the models is practically indistinguishable from one another using the present data. The foregoing statements apply to the eight dominant astronomical tides M2, S2, N2, K2, K1, O1, P1, and Q1. Variance reduction statistics for smaller tides are generally not accurate enough to differentiate the models’ performance.

scholarly journals Extraction of Tide Constituents by Harmonic Analysis Using Altimetry Satellite Data in the Brazilian Coast

2015 ◽  
Vol 32 (3) ◽  
pp. 614-626 ◽  
Author(s):  
Victor Bastos Daher ◽  
Rosa Cristhyna de Oliveira Vieira Paes ◽  
Gutemberg Borges França ◽  
João Bosco Rodrigues Alvarenga ◽  
Gregório Luiz Galvão Teixeira
Keyword(s):  
Harmonic Analysis ◽  
Shallow Water ◽  
Deep Water ◽  
Global Ocean ◽  
Ocean Tide ◽  
Brazilian Coast ◽  
Latitude Range ◽  
Comparison Results ◽  
Major Discrepancy ◽  
Tidal Constituents

AbstractThis paper analyzes the sea surface height dataset from the TOPEX, Jason-1, and Jason-2 satellites of a 19-yr time series in order to extract the tide harmonic constituents for the region limited by latitude 5°N–35°S and longitude 55°–20°W. The harmonic analysis results implemented here were compared with the tidal constituents estimated by three classical tidal models [i.e., TOPEX/Poseidon Global Inverse Solution 7.2 (TPXO7.2), Global Ocean Tide 4.7 (GOT4.7), and Finite Element Solution 2102 (FES2102)] and also with those extracted from in situ measurements. The Courtier criterion was used to define the tide regimes and regionally they are classified as semidiurnal between the latitude range from approximately 5°N to 22°S, semidiurnal with diurnal inequality from 22° to about 29°S, and mixed southward of latitude 22°S. The comparison results among all tide approaches were done by analyzing the root-sum-square misfit (RSSmisfit) value. Generally, the RSSmisfit difference values are not higher than 12 cm among them in deep-water regions. On the other hand, in shallow water, all models have presented quite similar performance, and the RSSmisfit values have presented higher variance than the previous region, as expected. The major discrepancy results were particularly noted for two tide gauges located in the latitude range from 5°N to 2°S. The latter was investigated and conclusions have mainly pointed to the influence of the mouth of the Amazon River and the considerable distance between tide measurements and the satellite reference point, which make it quite hard to compare those results. In summary, the results have showed that all models presently generate quite reliable results for deep water; however, further study should done in order to improve them in shallow-water regions too.

scholarly journals THREE-DIMENSIONAL SIMULATION OF TIDAL CURRENT IN LAMPUNG BAY: DIAGNOSTIC NUMERICAL EXPERIMENTS

2010 ◽  
Vol 3 (-) ◽  
Author(s):  
Alan Frendy Koropitan ◽  
Safwan Hadi ◽  
Ivonne M.Radjawane
Keyword(s):  
Tidal Current ◽  
Lower Layer ◽  
Three Dimensional ◽  
Ocean Model ◽  
Residual Current ◽  
Global Ocean ◽  
Open Boundary ◽  
Ocean Tide ◽  
Tidal Elevation ◽  
Diagnostic Mode

Princeton Ocean Model (POM) was used to calculate the tidal current in Lampung Bay using diagnostic mode. The model was forced by tidal elevation, which was given along the open boundary using a global ocean tide model-ORITIDE. The computed tidal elevation at St. 1 and St 2 are in a good agreement with the observed data, but the computed tidal current at St 1 at depth 2 m is not good and moderate approximation is showed at depth 10 m. Probably, it was influenced by non-linier effect of coastal geometry and bottom friction because of the position of current meter, mooring closed to the coastline. Generally, the calculated tidal currents in all layers show that the water flows into the bay during flood tide and goes out from the bay during ebb tide. The tidal current becomes strong when passing through the narrow passage of Pahawang Strait. The simulation of residual tidal current with particular emphasis on predominant contituent of M2 shows a strong inflow from the western part of the bay mouth, up to the central part of the bay, then the strong residual current deflects to the southeast and flows out from the eastern part of the bay mouth. This flow pattern is apparent in the upper and lower layer. The other part flows to the bay head and froms an antic lockwise circulation in the small basin region of the bay head. The anticlockwise circulations are showed in the upper layer and disappear in the layer near the bottom. Keywords: POM, diagnostic mode, tidal current, residual current, Lampung Ba.

scholarly journals Research Article. Towards a tidal loading model for the Argentine-German Geodetic Observatory (La Plata)

2017 ◽  
Vol 7 (1) ◽  
Author(s):  
A. Richter ◽  
L. Müller ◽  
E. Marderwald ◽  
L. Mendoza ◽  
E. Kruse ◽  
...  
Keyword(s):  
Earth Tides ◽  
Global Ocean ◽  
Ocean Tide ◽  
Observation Data ◽  
Additional Contribution ◽  
La Plata ◽  
Ocean Tide Model ◽  
Tide Model ◽  
Loading Effects ◽  
Tidal Loading

AbstractWe present a regionalized model of ocean tidal loading effects for the Argentine-German Geodetic Observatory in La Plata. It provides the amplitudes and phases of gravity variations and vertical deformation for nine tidal constituents to be applied as corrections to the observatory’s future geodetic observation data. This model combines a global ocean tide model with a model of the tides in the Río de la Plata estuary. A comparison with conventional predictions based only on the global ocean tide model reveals the importance of the incorporation of the regional tide model. Tidal loading at the observatory is dominated by the tides in the Atlantic Ocean. An additional contribution of local tidal loading in channels and groundwater is examined. The magnitude of the tidal loading is also reviewed in the context of the effects of solid earth tides, atmospheric loading and non-tidal loads.

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