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 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>

New unconstrained global ocean tide solutions for satellite gravimetry including minor tides

2020 ◽  
Author(s):  
Roman Sulzbach ◽  
Henryk Dobslaw ◽  
Maik Thomas
Keyword(s):  
Numerical Models ◽  
Signal To Noise Ratio ◽  
Column Height ◽  
Global Ocean ◽  
Ocean Tide ◽  
Data Sets ◽  
Satellite Gravimetry ◽  
The North ◽  
The Individual ◽  
Ocean Tide Models

<p>The quality of global ocean tide models has increased drastically over the last decades due to the availability of dense open-ocean observations from satellite altimetry. In regions of poor altimetry coverage (e.g., polar seas and coastal areas) and for minor tides with a small signal-to-noise ratio, however, reliable estimates from unconstrained global numerical models are still (and will remain) critically important. We will present in this contribution recent results from the purely-hydrodynamic, barotropic tidal model TiME (Weis et al., 2008) that benefit from a newly introduced rotated grid avoiding the singularity at the North Pole; a revised scheme for dynamic feedbacks of self-attraction and loading; and revised bathymetry data-sets that also include water column height modifications in cavities underneath the Antarctic ice-shelves.</p><p>By focussing exemplarily on the M<sub>2</sub> tide, we will demonstrate the individual impact of all those changes on the simulated water height variations. It will be shown that the effects of ice-shelf cavities extend well beyond the Southern Ocean and affect even amphidromic systems in the Northern Hemisphere. We will also emphasize the ability of unconstrained numerical models as TiME to explicitly simulate minor tidal lines, thereby allowing to thoroughly test (and subsequently improve) admittance-based methods currently employed for the processing of satellite gravimetry data from the GRACE and GRACE-FO missions.</p>

scholarly journals On the Resonance and Shelf/Open-Ocean Coupling of the Global Diurnal Tides

2013 ◽  
Vol 43 (7) ◽  
pp. 1301-1324 ◽  
Author(s):  
Aaron W. Skiba ◽  
Libo Zeng ◽  
Brian K. Arbic ◽  
Malte Müller ◽  
William J. Godwin
Keyword(s):  
Sea Of Okhotsk ◽  
Open Ocean ◽  
Ice Age ◽  
Global Ocean ◽  
Ocean Tide ◽  
Free Oscillations ◽  
Tidal Forcing ◽  
Tide Model ◽  
Ocean Tide Models ◽  
Diurnal Tides

Abstract The resonance of diurnal tidal elevations is investigated with a forward ocean tide model run in a realistic near-global domain and a synthesis of free oscillations (normal modes) computed for realistic global ocean geometries and ocean physics. As a prelude to performing the forward ocean tide simulations, the topographic wave drag, which is now commonly employed in forward ocean tide models, is tuned specifically for diurnal tides. The synthesis of global free oscillations predicts reasonably well the forward ocean diurnal tide model sensitivity to changes in the frequency, zonal structure, and meridional structure of the astronomical diurnal tidal forcing. Three global free oscillations that are important for understanding diurnal tides as a superposition of forced-damped, resonant, free oscillations are identified. An admittance analysis of the frequency sweep experiments demonstrates that some coastal locations such as the Sea of Okhotsk are resonant to diurnal tidal forcing. As in earlier work done with semidiurnal tides, a series of simulations are performed in which regions possessing significant coastal diurnal tides are blocked out. The largest perturbations to the open-ocean diurnal tides take place in Blocked Sea of Okhotsk experiments. Lesser but still significant perturbations also arise from the blocking out of other regions of large diurnal tidal elevations or dissipation. Interpretation of the results is made more complex, however, by the fact that substantial perturbations also arise from blocking out regions where neither tidal elevations nor dissipation are large. The “blocking” experiments are relevant to understanding tides of the ice age, during which lower sea levels entail a reduced area of continental shelves.

Tides of the Ross Sea and Ross Ice Shelf cavity

2003 ◽  
Vol 15 (1) ◽  
pp. 31-40 ◽  
Author(s):  
LAURENCE PADMAN ◽  
SVETLANA EROFEEVA ◽  
IAN JOUGHIN
Keyword(s):  
Ross Sea ◽  
Spring Tide ◽  
Model Performance ◽  
Tidal Currents ◽  
Tidal Range ◽  
Ocean Tide ◽  
Shelf Area ◽  
Ice Shelf ◽  
Ross Ice Shelf ◽  
Ocean Tide Models

Two new ocean tide models for the Ross Sea including the ocean cavity under the Ross Ice Shelf, are described. The optimum model for predicting ice shelf surface height variability is based on assimilation of gravimetry-derived tidal constituents from the Ross Ice Shelf. Synthetic aperture radar interferograms provide an independent test of model performance. The standard deviation of tide height variability is largest under the eastern ice shelf along the Shirase and Siple Coasts, where it can exceed 0.8 m. The maximum peak-to-peak tidal range in this region is ∼3 m. The best predictor for ocean tidal currents north of the ice front is a dynamics-based model that solves the depth-integrated shallow water equations with a linear representation of benthic friction rather than the more usual quadratic form. Tidal currents over the open Ross Sea are dominated by diurnal, topographically trapped vorticity waves. The strongest modelled currents exceed 1 m s−1 at spring tide in a narrow band along the upper continental slope in the north-western Ross Sea. Typical tidal currents in the central continental shelf area of the Ross Sea are 10–20 cm s−1. Under the ice shelf the typical currents are ∼5 cm s−1.

scholarly journals ACCURACY ASSESSMENT OF RECENT GLOBAL OCEAN TIDE MODELS AROUND ANTARCTICA

2017 ◽  
Vol XLII-2/W7 ◽  
pp. 1521-1528 ◽  
Author(s):  
J. Lei ◽  
F. Li ◽  
S. Zhang ◽  
H. Ke ◽  
Q. Zhang ◽  
...  
Keyword(s):  
Accuracy Assessment ◽  
Weddell Sea ◽  
Global Ocean ◽  
Ocean Tide ◽  
Polar Regions ◽  
Ice Shelf ◽  
Ice Shelves ◽  
Ross Ice Shelf ◽  
Shelf Region ◽  
Ocean Tide Models

Due to the coverage limitation of T/P-series altimeters, the lack of bathymetric data under large ice shelves, and the inaccurate definitions of coastlines and grounding lines, the accuracy of ocean tide models around Antarctica is poorer than those in deep oceans. Using tidal measurements from tide gauges, gravimetric data and GPS records, the accuracy of seven state-of-the-art global ocean tide models (DTU10, EOT11a, GOT4.8, FES2012, FES2014, HAMTIDE12, TPXO8) is assessed, as well as the most widely-used conventional model FES2004. Four regions (Antarctic Peninsula region, Amery ice shelf region, Filchner-Ronne ice shelf region and Ross ice shelf region) are separately reported. The standard deviations of eight main constituents between the selected models are large in polar regions, especially under the big ice shelves, suggesting that the uncertainty in these regions remain large. Comparisons with in situ tidal measurements show that the most accurate model is TPXO8, and all models show worst performance in Weddell sea and Filchner-Ronne ice shelf regions. The accuracy of tidal predictions around Antarctica is gradually improving.

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