Convergence of Daily GRACE Solutions and Models of Submonthly Ocean Bottom Pressure Variability

Schindelegger, Michael; Harker, Alexander; Ponte, Rui M.; Dobslaw, Henryk; Salstein, David A.

doi:10.1029/2020jc017031

Cited by 22 publications

(31 citation statements)

References 61 publications

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“…Explorations of this kind are important, as they inform broader OAM modeling efforts (by ESMGFZ and ECCO) of avenues that are likely to give reward. Results here and elsewhere (Weijer 2010;Schindelegger et al 2021) suggest that refining horizontal grid spacing from 1 • to ∼ 1 ⁄3 • improves the representation of barotropic variability in the Southern Ocean, which projects strongly on polar motion. Transitioning of the ECCO state estimates to the LLC270 grid is underway (Zhang et al 2018) and will cast light on this very issue.…”

Section: Summary Remarks and Outlookmentioning

confidence: 52%

“…We also consider results from a simple shallow-water model, referred to as DEBOT (David Einšpigel's Barotropic Ocean Tide model, Einšpigel and Martinec 2017) and operated on a 1 ⁄3 • latitude-longitude grid. The specific setup is that described by Schindelegger et al (2021) in the context of a study of global bottom pressure variability on sub-monthly time scales. ERA-Interim sea-level pressure and prognostic wind stress fields are used as forcing variables and dissipation is centered over topographic features through a linear wave drag scheme.…”

Section: Debotmentioning

confidence: 99%

“…ERA-Interim sea-level pressure and prognostic wind stress fields are used as forcing variables and dissipation is centered over topographic features through a linear wave drag scheme. From the two model runs conducted in Schindelegger et al (2021), we take the 2007-2009 integration without ocean self-attraction and loading (SAL) effects and extend it by 2 more years. Previous studies (e.g., Quinn et al 2019) have conjectured that the dynamic feedbacks associated with the SAL term might entail relevant OAM signals.…”

Section: Debotmentioning

confidence: 99%

“…4.3 draws on regularized daily GRACE gravity field determinations by ITSG (Institute of Geodesy at Graz University of Technology, release ITSG-Grace2018, Mayer-Gürr et al 2018; Kvas et al 2019). While being no "ground truth" in the strict sense of the word, these solutions provide a more realistic depiction of large-scale sub-monthly mass-field variability than their de-aliasing priors, down to periods of 4-5 days; see Schindelegger et al (2021) and references therein. As in the latter study, we map the ITSG-Grace2018 spherical harmonics coefficients for degrees n = 2 .…”

Section: Other Data Setsmentioning

confidence: 99%

See 3 more Smart Citations

Modeling ocean-induced rapid Earth rotation variations: an update

Harker

Schindelegger

Ponte

et al. 2021

J Geod

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We revisit the problem of modeling the ocean’s contribution to rapid, non-tidal Earth rotation variations at periods of 2–120 days. Estimates of oceanic angular momentum (OAM, 2007–2011) are drawn from a suite of established circulation models and new numerical simulations, whose finest configuration is on a "Image missing"$$^\circ $$ ∘ grid. We show that the OAM product by the Earth System Modeling Group at GeoForschungsZentrum Potsdam has spurious short period variance in its equatorial motion terms, rendering the series a poor choice for describing oceanic signals in polar motion on time scales of less than $$\sim $$ ∼ 2 weeks. Accounting for OAM in rotation budgets from other models typically reduces the variance of atmosphere-corrected geodetic excitation by $$\sim $$ ∼ 54% for deconvolved polar motion and by $$\sim $$ ∼ 60% for length-of-day. Use of OAM from the "Image missing"$$^\circ $$ ∘ model does provide for an additional reduction in residual variance such that the combined oceanic–atmospheric effect explains as much as 84% of the polar motion excitation at periods < 120 days. Employing statistical analysis and bottom pressure changes from daily Gravity Recovery and Climate Experiment solutions, we highlight the tendency of ocean models run at a 1$$^\circ $$ ∘ grid spacing to misrepresent topographically constrained dynamics in some deep basins of the Southern Ocean, which has adverse effects on OAM estimates taken along the 90$$^\circ $$ ∘ meridian. Higher model resolution thus emerges as a sensible target for improving the oceanic component in broader efforts of Earth system modeling for geodetic purposes.

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Section: Summary Remarks and Outlookmentioning

confidence: 52%

Section: Debotmentioning

confidence: 99%

Section: Debotmentioning

confidence: 99%

Section: Other Data Setsmentioning

confidence: 99%

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Modeling ocean-induced rapid Earth rotation variations: an update

Harker

Schindelegger

Ponte

et al. 2021

J Geod

Self Cite

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“…Notable examples are the Kalman smoother approach by [8], a moving window approach by [9], constrained surface mass estimates from the Center of Space Research (CSR) [10] and a Kalman filter approach for regional applications [11]. Data sets dervied with these approaches have seen various applications in Earth system sciences, for example, analysis of large scale flood events [12], evaluation of geophysical models [13,14] or near real-time flood monitoring [15].…”

Section: Introductionmentioning

confidence: 99%

Regularization of the Gravity Field Inversion Process with High-Dimensional Vector Autoregressive Models

Kvas

Mayer‐Gürr

2021

The 40th International Workshop on Bayesian Inference and Maximum Entropy Methods in Science and Engineering

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Earth’s gravitational field provides invaluable insights into the changing nature of our planet. It reflects mass change caused by geophysical processes like continental hydrology, changes in the cryosphere or mass flux in the ocean. Satellite missions such as the NASA/DLR operated Gravity Recovery and Climate Experiment (GRACE), and its successor GRACE Follow-On (GRACE-FO) continuously monitor these temporal variations of the gravitational attraction. In contrast to other satellite remote sensing datasets, gravity field recovery is based on geophysical inversion which requires a global, homogeneous data coverage. GRACE and GRACE-FO typically reach this global coverage after about 30 days, so short-lived events such as floods, which occur on time frames from hours to weeks, require additional information to be properly resolved. In this contribution we treat Earth’s gravitational field as a stationary random process and model its spatio-temporal correlations in the form of a vector autoregressive (VAR) model. The satellite measurements are combined with this prior information in a Kalman smoother framework to regularize the inversion process, which allows us to estimate daily, global gravity field snapshots. To derive the prior, we analyze geophysical model output which reflects the expected signal content and temporal evolution of the estimated gravity field solutions. The main challenges here are the high dimensionality of the process, with a state vector size in the order of 103 to 104, and the limited amount of model output from which to estimate such a high-dimensional VAR model. We introduce geophysically motivated constraints in the VAR model estimation process to ensure a positive-definite covariance function.

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Global Ocean Response to the 5-Day Rossby-Haurwitz Atmospheric Mode Seen by GRACE

Ponte

Schindelegger

2021

Preprint

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A dynamic response of the ocean to surface pressure loading by the well-known 5-day Rossby-Haurwitz mode in the atmosphere has been inferred from limited in situ tide gauge and bottom pressure data, but a global characterization of such response, including details at mid and high latitudes, has been lacking. Here we explore two daily data products from the Gravity Recovery and Climate Experiment (GRACE) mission to obtain a first quasi-global look at the associated ocean bottom pressure (OBP) signals at 5-day period. The previously reported in-phase behavior over the Atlantic basin, seesaw between the Atlantic and Pacific, and westward propagation in the Pacific are all seen in the GRACE solutions. Other previously unknown features include relatively strong responses in the Southern Ocean and also some shallow coastal regions (e.g., North Sea, East Siberian shelf, Patagonian shelf). Correlation analysis points to the Rossby-Haurwitz surface pressure wave as the main forcing for the observed large-scale OBP anomalies, while wind-driven signals are more spatially confined. The GRACE observations are found to be consistent with in situ OBP data and also with model simulations of the 5-day ocean variability where no in situ data is available. Inferences on energetics based on data and model results point to decay time scales shorter than the oscillation period, with substantial kinetic energy and dissipation located over a few topographic features in the Southern Ocean. Results illustrate the potential of space gravity measurements for examining large-scale oceanic variability at sub-weekly periods.

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Convergence of Daily GRACE Solutions and Models of Submonthly Ocean Bottom Pressure Variability

Cited by 22 publications

References 61 publications

Modeling ocean-induced rapid Earth rotation variations: an update

Modeling ocean-induced rapid Earth rotation variations: an update

Regularization of the Gravity Field Inversion Process with High-Dimensional Vector Autoregressive Models

Global Ocean Response to the 5-Day Rossby-Haurwitz Atmospheric Mode Seen by GRACE

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