Aliasing of ocean tides in satellite gravimetry: a two-step mechanism

Liu, Wei; Sneeuw, Nico

doi:10.1007/s00190-021-01586-6

Cited by 8 publications

(3 citation statements)

References 27 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In our study, we did not consider the impact of tides and did not eliminate the aspect of tidal aliasing, which is one of the largest source of error in satellite gravimetry (Liu and Sneeuw 2021) and would require a tidal model for the WTNA. On the other hand, a careful inspection of the tidal constituents of the M 2 , S 2 , N 2 , and K 2 tides (Beardsley et al 1995;Hart-Davis et al 2021) indicated strong tidal signals on the Amazon shelf where the water depth is < 20 m. This area is a relatively small part of the Amazon shelf and the small phase variation of tidal currents and surface elevation across the shelf suggest that the semi diurnal tide is a strongly damped standing wave (Geyer et al 1991), which might contribute to the meandering structure observed in the M174 SSS figures.…”

Section: Discussionmentioning

confidence: 99%

The Amazon River plume—a Lagrangian view

Dippner,

Montoya,

Subramaniam

et al. 2024

Limnology & Ocean Methods

View full text Add to dashboard Cite

Hydrographic data, nutrient data and bulk rates of nitrate uptake and primary production were determined in the Amazon River plume (ARP) in the Western Tropical North Atlantic (WTNA) during three cruises in May 2018, June/July 2019, with RV Endeavor and April/May 2021 with RV Meteor. Using daily quasi‐geostrophic surface velocity data from satellite observations, the geographical positions of the stations of observations were transformed onto Lagrangian coordinates to obtain a dynamically coherent and consistent spatial distribution. After the transformation, the observed surface salinity and temperature fields were consistent with the flow fields, the ARP formed a coherent structure and the retroflection of the North Brazil Current became visible. By transforming other surface variables such as nitrate concentration, photosynthetically available radiation, turbidity, bulk rates of nitrate uptake, and primary production onto Lagrangian coordinates, patterns became consistent with the physical variables at the surface. The use of “synchronous” fields as done here by transformation onto Lagrangian coordinates is essential for spatially structured analyses of data collected over tens of days in a highly dynamic region characterized by complex flow fields with low persistence such as the WTNA. Therefore, the use of the Lagrangian method provides a powerful tool for exploring spatial distributions of biologically relevant factors in regions with complex and dynamic flow patterns. These spatial distributions are qualitatively in agreement with satellite images of daily sea surface temperature and composites of monthly mean Chlorophyll a distributions.

show abstract

Section: Discussionmentioning

confidence: 99%

The Amazon River plume—a Lagrangian view

Dippner,

Montoya,

Subramaniam

et al. 2024

Limnology & Ocean Methods

View full text Add to dashboard Cite

show abstract

“…Otherwise, a highfrequency signal will map into lower frequency due to the incomplete sampling and result in sampling a false signal with longer period. Aliasing in satellite gravimetry is induced by a more complicated two-step mechanism [6]. The primary aliasing is caused by orbit under-sampling of original high frequency signals and the secondary aliasing is due to under-sampling of the primary aliasing signals through gravity recovery in discrete (monthly) time intervals.…”

Section: Introductionmentioning

confidence: 99%

On Tide Aliasing in GRACE Time-Variable Gravity Observations

Zhang

Wang

2022

Remote Sensing

View full text Add to dashboard Cite

Aliasing error induced by tide-related high frequency mass variations is one of the most significant errors in the Gravity Recovery and Climate Experiment (GRACE). In the present work, we evaluated the 161.0-day S2, 171.2-day P1, and 322.1-day S1 ocean tide aliasing in GRACE latest RL06 data based on nearly 15 years of observation from 2002 to 2017. Tide aliasing was still obvious for current GRACE observations, especially for S2 and P1 aliasing. S2 aliasing was mostly evident over West Antarctica, and was a clearly eastward propagation that travelled around Antarctica in about 2 years, while P1 showed strongest aliasing over South Greenland. More seriously, we found that GRACE mascon data showed an extremely large aliasing error. The mascon data may have unintentionally amplified the aliasing error on land due to the regularization (or constraint) applied for reducing signal leakage. Enough attention must be paid to tide aliasing when using GRACE for assessing mass variations at high latitudes (e.g., glaciers in polar regions) which can cause potential obstacles to estimation of actual seasonality.

show abstract

“…An a posteriori method for de-aliasing of OT errors in future double-pair missions was proposed by Liu et al (2016), also giving hints about optimal choices for orbit constellations to mitigate OT aliasing effects. Liu & Sneeuw (2021) describe OT aliasing as a two-step mechanism, with orbit sampling as the first step and gravity recovery as the second step. Another promising approach is the direct estimation of selected OT constituents.…”

mentioning

confidence: 99%

Treatment of ocean tide background model errors in the context of GRACE/GRACE-FO data processing

Abrykosov

Sulzbach

Pail

et al. 2022

Preprint

View full text Add to dashboard Cite

Due to its high-frequency, high-amplitude nature the ocean tide (OT) signal poses a core limitation within the GRACE/GARCE-FO data processing, as its temporal undersampling ultimately results in the typical striping pattern. To some degree this issue can be resolved by employing a-priori de-aliasing based on an OT background model. However, due to model errors and imperfections some residual effects inevitably remain within the resulting gravity product. So far, the background models have been assumed as error-free within the data processing. Since ocean tide models feature distinct, time-invariant spatial error patterns (low uncertainties in open oceans, high uncertainties in coastal and high-latitude regions), it is reasonable to assume that weighting the observations based on the underlying spatial error shall result in a more homogenous gravity solution. Thus, error co-variance matrices are derived for the spherical harmonic coefficients representing the eight principal tides based on a set of five modern-day OT models and propagated onto the level of observations. This error information is then employed within the least-squares parameter estimation for the final gravity product. The functionality of this approach is verified through closed-loop simulations and its limitations are discussed. Results are presented for single-pair-based gravity retrieval scenarios.

show abstract

Aliasing of ocean tides in satellite gravimetry: a two-step mechanism

Cited by 8 publications

References 27 publications

The Amazon River plume—a Lagrangian view

The Amazon River plume—a Lagrangian view

On Tide Aliasing in GRACE Time-Variable Gravity Observations

Treatment of ocean tide background model errors in the context of GRACE/GRACE-FO data processing

Contact Info

Product

Resources

About