Improved 90-day Earth orientation predictions from angular momentum forecasts of atmosphere, ocean, and terrestrial hydrosphere

Dill, Robert; Dobslaw, Henryk; Thomas, Maik

doi:10.1007/s00190-018-1158-7

Cited by 51 publications

(47 citation statements)

References 32 publications

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“…latest configuration as applied for the prediction of Earth rotation excitations (Dill et al 2018). Over the oceans, we utilize the Max-Planck Institute Ocean Model (MPIOM; Jungclaus et al 2013) in its configuration for the latest release 06 of AOD1B (Dobslaw et al 2017).…”

Section: E Va L Uat I N G T H E I T S G -G R a C E 2 0 1 6 Da I Ly K A L M A N S M O O T H E R S O L U T I O N Smentioning

confidence: 99%

Mitigating temporal aliasing effects of high-frequency geophysical fluid dynamics in satellite gravimetry

Poropat

Kvas

Mayer‐Gürr

et al. 2019

Geophysical Journal International

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SUMMARY Temporal aliasing errors induced by high-frequency tidal and non-tidal mass variability in the Earth system are among the three most important error sources that limit the accuracy of present-day surface mass estimates from satellite gravimetry. By means of end-to-end simulations, we demonstrate that the Kalman Smoother approach developed by Kurtenbach et al. effectively captures non-tidal submonthly variability, and thereby reduces temporal aliasing errors way beyond the level of simply subtracting the standard dealiasing model AOD1B. Validation against in situ ocean bottom pressure observations confirms that the Kalman Smoother solutions published together with the ITSG-Grace2016 monthly gravity fields contain high-frequency signal over the oceans not predicted by AOD1B. The daily gravity fields therefore reduce aliasing artefacts in the monthly gravity fields, and at the same time provide observational evidence on submonthly bottom pressure variability presently not reflected in state-of-the-art numerical ocean circulation models. It is thus recommended to include a Kalman Smoother approach into any standard GRACE processing scheme. For a hypothetical double-pair configuration currently under consideration as a future mass change mission, we find that the benefit of the Kalman Smoother is much smaller thanks to the increased number of observations taken at different inclinations, which lead to generally reduced aliasing errors and much more isotropic spatial error correlations. We also reassess the idea of pre-eliminating low-resolution daily gravity fields and find large distortions in the monthly mean gravity solution at spatial wavelengths around the cut-off-degree of the daily fields. We thus recommend further study for any satellite gravity mission concept that critically relies on such pre-elimination schemes for reaching its science objectives.

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Section: E Va L Uat I N G T H E I T S G -G R a C E 2 0 1 6 Da I Ly K A L M A N S M O O T H E R S O L U T I O N Smentioning

confidence: 99%

Mitigating temporal aliasing effects of high-frequency geophysical fluid dynamics in satellite gravimetry

Poropat

Kvas

Mayer‐Gürr

et al. 2019

Geophysical Journal International

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“…Moreover, mass redistributions in the ocean cause perturbations to the angular momentum of Earth's fluid envelope, which manifests in orientation changes of the solid Earth with respect to inertial space (e.g., Ponte & Ali, 2002). Forecasts of these short‐term ocean angular momentum variations are particularly relevant for operational activities like real‐time spacecraft navigation or tracking of deep‐space objects (Dill et al., 2019). Fluctuations of ocean bottom pressure ( p b ), equivalent to the anomalous mass in the column of fluid above, and its spatial gradients are also of interest to physical oceanographers.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2021

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The Gravity Recovery and Climate Experiment (GRACE) and its follow-on mission (GRACE-FO; Tapley et al., 2019) have been providing a unique series of measurements of temporal gravity variations at large spatial scales. The technique has rung in a new era in the ability to quantify mass anomalies and fluxes across the Earth system, including changes in terrestrial water storage (Rodell et al., 2018), temporal variations in ocean circulation (Zlotnicki et al., 2007), the mass balance of ice sheets (Velicogna et al., 2020), and manometric contributions to regional sea level (Rietbroek et al., 2016). Although the satellites are orbiting the Earth once in 90 min, it typically takes 1 month for the ground track coverage to become dense enough such that the data can be inverted for a full global gravity field. Mass variations associated with geophysical phenomena on time scales shorter than the nominal GRACE Nyquist frequency (0.5 cyc/

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“…An example is the torques on the rotating Earth derived from global integrations of the angular momentum variations in the atmospheric and oceanic circulations available in the public domain by Centre of Global Geophysical Fluids (GGFC). [ 12–17 ] Observation noises and numerical rounding errors are generic sources to limit the smoothness of the derived forcing. Here, we ignore the errors and discuss the physical smoothness.…”

Section: Physical Smoothness Of the Applied Forcing: A Case Study Witmentioning

confidence: 99%

On the Eigen‐Mode Excitation of Linear Oscillators and the Earth's Polar Motion

Fang

Liao

2020

Annalen der Physik

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By transforming a 1D second‐order linear oscillator into a 2D first‐order polar motion differential equation, it can be shown that the finite smoothness (i.e., the presence of jump in finite order derivatives) of the applied Newtonian forcing constitutes the sufficient and necessary condition for instantaneous excitation of free eigen‐mode. This condition can be met by forcing functions originated from turbulent and multiphase fluid motions. Sub‐macroscopic transition time associated with astatic elastic deformation limits the physical smoothness of the applied forcing for the Earth's polar motion. Eigen‐modes can also be excited by an infinitely smooth forcing that has a finite domain of non‐zero values. The eigen‐period serves as a macroscopic timescale to characterize the inertia of a linear oscillator. If a zero mean irregular forcing of finite smoothness exhibits a high degree of randomness and the timescale is much shorter than the eigen‐period, then for negligible damping the eigen‐waveform will increase in proportion to the squareroot of time, while the waveform distortion is statistically a constant. As a result, the pattern of distinctive eigen‐oscillation will dominate the forced solution for longer enough duration.

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Improved 90-day Earth orientation predictions from angular momentum forecasts of atmosphere, ocean, and terrestrial hydrosphere

Cited by 51 publications

References 32 publications

Mitigating temporal aliasing effects of high-frequency geophysical fluid dynamics in satellite gravimetry

Mitigating temporal aliasing effects of high-frequency geophysical fluid dynamics in satellite gravimetry

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

On the Eigen‐Mode Excitation of Linear Oscillators and the Earth's Polar Motion

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