scholarly journals EOT20: A global ocean tide model from multi-mission satellite altimetry

2021 ◽  
Author(s):  
Michael Geoffrey Hart-Davis ◽  
Gaia Piccioni ◽  
Denise Dettmering ◽  
Christian Schwatke ◽  
Marcello Passaro ◽  
...  
Keyword(s):  
Satellite Altimetry ◽  
Variance Reduction ◽  
Coastal Region ◽  
Global Ocean ◽  
Ocean Tide ◽  
Ocean Bottom ◽  
Ocean Tide Model ◽  
Mission Satellite ◽  
Tidal Constituents ◽  
Tidal Correction

Abstract. EOT20 is the latest in a series of empirical ocean tide (EOT) models derived using residual tidal analysis of multi-mission satellite altimetry at DGFI-TUM. The amplitudes and phases of seventeen tidal constituents are provided on a global 0.125-degree grid based on empirical analysis of seven satellite altimetry missions and four extended missions. The EOT20 model shows significant improvements compared to the previous iteration of the global model (EOT11a) throughout the ocean, particularly in the coastal and shelf regions, due to the inclusion of more recent satellite altimetry data as well as more missions, the use of the updated FES2014 tidal model as a reference to estimated residual signals, the inclusion of the ALES retracker and improved coastal representation. In the validation of EOT20 using tide gauges and ocean bottom pressure data, these improvements in the model compared to EOT11a are highlighted with the root-square sum (RSS) of the eight major tidal constituents improving by ~3 cm for the entire global ocean with the major improvement in RSS (~3.5 cm) occurring in the coastal region. Concerning the other global ocean tidal models, EOT20 shows an improvement of ~0.2 cm in RSS compared to the closest model (FES2014) in the global ocean. Variance reduction analysis was conducted comparing the results of EOT20 with FES2014 and EOT11a using the Jason-2, Jason-3 and SARAL satellite altimetry missions. From this analysis, EOT20 showed a variance reduction for all three satellite altimetry missions with the biggest improvement in variance occurring in the coastal region. These significant improvements, particularly in the coastal region, provides encouragement for the use of the EOT20 model as a tidal correction for satellite altimetry in sea-level research. All ocean and load tide data from the model can be freely accessed at https://doi.org/10.17882/79489 (Hart-Davis et al., 2021).

EOT20: A new global empirical ocean tide model derived from multi-mission satellite altimetry.

2021 ◽  
Author(s):  
Michael Hart-Davis ◽  
Denise Dettmering ◽  
Gaia Piccioni ◽  
Christian Schwatke ◽  
Marcello Passaro ◽  
...  
Keyword(s):  
Satellite Altimetry ◽  
Coastal Region ◽  
Global Ocean ◽  
Ocean Tide ◽  
Ocean Bottom ◽  
Ocean Tide Model ◽  
Mission Satellite ◽  
Coastal Sea ◽  
Tidal Constituents ◽  
Tidal Correction

<p>EOT20 is the latest in a series of empirical ocean tide (EOT) models derived using residual tidal analysis of multi-mission satellite altimetry at DGFI-TUM. The amplitudes and phases of seventeen tidal constituents are provided on a global 0.125-degree grid based on empirical analysis of eleven satellite altimetry missions. The EOT20 model shows significant improvements compared to the previous iteration of the global model (EOT11a) throughout the ocean, particularly in the coastal and shelf regions, due to the inclusion of more recent satellite altimetry data as well as more missions, the use of the updated FES2014 tidal model as a reference to estimated residual signals, the inclusion of the ALES retracker and improved coastal representation. In the validation of EOT20 using tide gauges and ocean bottom pressure data, these improvements in the model compared to EOT11a are highlighted with the root-square sum (RSS) of the eight major tidal constituents improving by ~3 cm for the entire global ocean with the major improvement in RSS (~3.5 cm) occurring in coastal regions (<1 km to the coast). Compared to the other global ocean tidal models, EOT20 shows a clear improvement of ~0.4 cm in RSS compared to the closest model (FES2014) in the global ocean. Compared to the FES2014 model, the RSS improvement in EOT20 is mainly seen in the coastal region (~0.45 cm) while in the shelf and open ocean regions these two models only vary in terms of RSS by ~0.005 cm. The significant improvement of EOT20, particularly in the coastal region, provides encouragement for the use of the EOT20 model as a tidal correction of satellite altimetry in coastal sea level research. </p>

scholarly journals EOT20: a global ocean tide model from multi-mission satellite altimetry

2021 ◽  
Vol 13 (8) ◽  
pp. 3869-3884
Author(s):  
Michael G. Hart-Davis ◽  
Gaia Piccioni ◽  
Denise Dettmering ◽  
Christian Schwatke ◽  
Marcello Passaro ◽  
...  
Keyword(s):  
Satellite Altimetry ◽  
Variance Reduction ◽  
Coastal Region ◽  
Global Ocean ◽  
Ocean Tide ◽  
Ocean Bottom ◽  
Tide Gauges ◽  
Tide Model ◽  
Mission Satellite ◽  
Tidal Constituents

Abstract. EOT20 is the latest in a series of empirical ocean tide (EOT) models derived using residual tidal analysis of multi-mission satellite altimetry at DGFI-TUM. The amplitudes and phases of 17 tidal constituents are provided on a global 0.125∘ grid based on empirical analysis of seven satellite altimetry missions and four extended missions. The EOT20 model shows significant improvements compared to the previous iteration of the global model (EOT11a) throughout the ocean, particularly in the coastal and shelf regions, due to the inclusion of more recent satellite altimetry data as well as more missions, the use of the updated FES2014 tidal model as a reference to estimated residual signals, the inclusion of the ALES retracker and improved coastal representation. In the validation of EOT20 using tide gauges and ocean bottom pressure data, these improvements in the model compared to EOT11a are highlighted with the root sum square (RSS) of the eight major tidal constituents improving by ∼ 1.4 cm for the entire global ocean with the major improvement in RSS (∼ 2.2 cm) occurring in the coastal region. Concerning the other global ocean tidal models, EOT20 shows an improvement of ∼ 0.2 cm in RSS compared to the closest model (FES2014) in the global ocean. Variance reduction analysis was conducted comparing the results of EOT20 with FES2014 and EOT11a using the Jason-2, Jason-3 and SARAL satellite altimetry missions. From this analysis, EOT20 showed a variance reduction for all three satellite altimetry missions with the biggest improvement in variance occurring in the coastal region. These significant improvements, particularly in the coastal region, provide encouragement for the use of the EOT20 model as a tidal correction for satellite altimetry in sea-level research. All ocean and load tide data from the model can be freely accessed at https://doi.org/10.17882/79489 (Hart-Davis et al., 2021). The tide gauges from the TICON dataset used in the validation of the tide model, are available at https://doi.org/10.1594/PANGAEA.896587 (Piccioni et al., 2018a).

scholarly journals Regional Evaluation of Minor Tidal Constituents for Improved Estimation of Ocean Tides

2021 ◽  
Vol 13 (16) ◽  
pp. 3310
Author(s):  
Michael G. Hart-Davis ◽  
Denise Dettmering ◽  
Roman Sulzbach ◽  
Maik Thomas ◽  
Christian Schwatke ◽  
...  
Keyword(s):  
Sea Level ◽  
Satellite Altimetry ◽  
Tide Gauge ◽  
Sea Surface ◽  
Global Ocean ◽  
Ocean Tide ◽  
Ocean Tides ◽  
Tidal Constituents ◽  
Ocean Tide Models ◽  
Tidal Correction

Satellite altimetry observations have provided a significant contribution to the understanding of global sea surface processes, particularly allowing for advances in the accuracy of ocean tide estimations. Currently, almost three decades of satellite altimetry are available which can be used to improve the understanding of ocean tides by allowing for the estimation of an increased number of minor tidal constituents. As ocean tide models continue to improve, especially in the coastal region, these minor tides become increasingly important. Generally, admittance theory is used by most global ocean tide models to infer several minor tides from the major tides when creating the tidal correction for satellite altimetry. In this paper, regional studies are conducted to compare the use of admittance theory to direct estimations of minor tides from the EOT20 model to identify which minor tides should be directly estimated and which should be inferred. The results of these two approaches are compared to two global tide models (TiME and FES2014) and in situ tide gauge observations. The analysis showed that of the eight tidal constituents studied, half should be inferred (2N2, ϵ2, MSF and T2), while the remaining four tides (J1, L2, μ2 and ν2) should be directly estimated to optimise the ocean tidal correction. Furthermore, for certain minor tides, the other two tide models produced better results than the EOT model, suggesting that improvements can be made to the tidal correction made by EOT when incorporating tides from the two other tide models. Following on from this, a new approach of merging tidal constituents from different tide models to produce the ocean tidal correction for satellite altimetry that benefits from the strengths of the respective models is presented. This analysis showed that the tidal correction created based on the recommendations of the tide gauge analysis provided the highest reduction of sea-level variance. Additionally, the combination of the EOT20 model with the minor tides of the TiME and FES2014 model did not significantly increase the sea-level variance. As several additional minor tidal constituents are available from the TiME model, this opens the door for further investigations into including these minor tides and optimising the tidal correction for improved studies of the sea surface from satellite altimetry and in other applications, such as gravity field modelling.

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>

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 The cavity under the Amery Ice Shelf, East Antarctica

2008 ◽  
Vol 54 (188) ◽  
pp. 881-887 ◽  
Author(s):  
B.K. Galton-Fenzi ◽  
C. Maraldi ◽  
R. Coleman ◽  
J. Hunter
Keyword(s):  
Water Column ◽  
Ocean Circulation ◽  
East Antarctica ◽  
Ocean Tide ◽  
Ice Shelf ◽  
Ice Shelves ◽  
Ocean Tide Model ◽  
Amery Ice Shelf ◽  
Tidal Constituents

AbstractOcean circulation under ice shelves and associated rates of melting and freezing are strongly influenced by the shape of the sub-ice-shelf cavity. We have refined an existing method and used additional in situ measurements to estimate the cavity shape under the Amery Ice Shelf, East Antarctica. A finite-element hydrodynamic ocean-tide model was used to simulate the major tidal constituents for a range of different sub-Amery Ice Shelf cavity water-column thicknesses. The data are adjusted in the largely unsurveyed southern region of the ice-shelf cavity by comparing the complex error between simulated tides and in situ tides, derived from GPS observations. We show a significant improvement in the simulated tides, with a combined complex error of 1.8 cm, in comparison with past studies which show a complex error of ∼5.3 cm. Our bathymetry incorporates ice-draft data at the grounding line and seismic surveys, which have provided a considerable amount of new data. This technique has particular application when the water column beneath ice shelves is inaccessible and in situ GPS data are available.

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 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.

scholarly journals A COMPARISON BETWEEN TIDAL CONSTITUENTS DERIVED FROM SATELLITE ALTIMETRY AND IN-SITU DATA AROUND PENINSULAR MALAYSIA

2021 ◽  
Vol 6 (24) ◽  
pp. 139-151
Author(s):  
Mohammad Hanif Hamden ◽  
Ami Hassan Md Din ◽  
Dudy Darmawan Wijaya
Keyword(s):  
Satellite Altimetry ◽  
Tide Gauge ◽  
Peninsular Malaysia ◽  
Ocean Tide ◽  
Tide Gauges ◽  
In Situ Data ◽  
Regional Area ◽  
Tidal Constituents ◽  
Hourly Observation

Satellite altimetry technology has been widely used in exploring Earth’s Ocean activities. Achieving a remarkable accuracy in measuring sea level for ocean tide analysis has led the local researchers to investigate more details on tidal behaviour in the regional area. This study is an attempt to assess the reliability of derived tidal constituents between satellite radar altimetry and in-situ data which is referred to as coastal tide gauges. Three satellite missions denoted as TOPEX class missions namely TOPEX, Jason-1, and Jason-2 were used to derive along-track sea surface height (SSH) time series over 23 years. Besides, four selected coastal tide gauges were used for tidal analysis and validation where the tidal data have at least 19 years of hourly observation. Derivation of tidal constituents from both satellite altimetry and tide gauges were executed by adopting the harmonic analysis method. The comparisons were made by calculating the Root Mean Square Misfit (RMSmisfit) of each tidal constituent between the nearest altimetry point to the tide gauges. After RMSmisfit, Root Sum Square (RSS) values of tidal constituents at each tide gauge were also calculated. The results displayed the RMSmisfit of tidal constituents agreed well with the selected tide gauges which are within 10 cm except for M2 constituents which recorded 10.2 cm. Pelabuhan Kelang tide gauge station showed the highest RSS value followed by Pulau Langkawi which recorded 21.2 cm and 9.8 cm, respectively. In conclusion, overall results can be inferred that the satellite-derived tidal constituents are likely to have good agreement with the selected tide gauge stations. Nevertheless, further analysis should be executed in determining high precision satellite-derived tidal constituents, especially in the complex regional area.

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