Tidal Geopotential Dependence on Earth Ellipticity and Seawater Density and Its Detection With the GRACE Follow‐On Laser Ranging Interferometer

Abstract

The ocean tide is the most energetic water mass redistribution changing the Earth's gravity field periodically once and twice per day. Its significant perturbation on motion of near-Earth orbiting satellites was reported soon after the birth of satellite geodesy (Kaula, 1966; Lambeck et al., 1974). For example, a few μ gal (10 −8 m/ s 2) of gravitational acceleration exerted by ocean tidal mass change on a satellite at 1,000 km altitude may yield several meters of perturbation with periods of several days or longer due to resonant amplification (Schwintzer, 1997). Since that time, accounting for tidal variations in the geopotential has been routine practice in global gravity field analysis and spacecraft orbit determination, a necessary first step to study other geophysical processes causing smaller perturbations (Lambeck, 1988; Petit & Luzum, 2010). Numerous ocean tide models have been developed on global and regional domains and at various spatial scales using hydrodynamic numerical modeling, in situ data, and satellite measurements (Stammer et al., 2014). In addition to satellite altimeter measurements of tidal sea level change (Le Provost et al., 1995), satellite gravity measurements of tidal mass change from Gravity Recovery and Climate Experiment (GRACE)

The Impact of New Accelerometer Transplant Data (ACH) on GRACE Follow‐On Along‐Orbit Inter‐Satellite Laser Ranging Observations and Monthly Time‐Variable Gravity and Mascon Solutions

“…The difference in LRI residuals between ACT and ACH indicates the modification of large‐scale spatial variability of along‐orbit time‐variable gravity signals due to the update by ACH (see Figure 1d), consistent with the frequency and time domain analyses. The change in low‐frequency or large‐scale spatial components of LRI residuals mainly affects the analysis of phenomena with long‐wavelength features like gravity changes caused by Earth's free oscillations (Ghobadi‐Far, Han, et al., 2019) and the impact of seawater variable density on computing geopotential from ocean tides (Han et al., 2020).…”

A Global Seawater Density Distribution Model Using a Convolutional Neural Network

“…Conversely, where the vertical profile varies little, the resolution is low, up to 50 dbar. (2) The majority of the floats operate within a pressure range of up to 2000 dbar from 2016. (3) The geographic distribution of samples offers almost complete ocean coverage.…”

“…Using a spatial distribution model for seawater density in the region of interest would significantly decrease errors in gravitational field modeling by using actual density distribution [ 1 ]. The effect of seawater density variations on tidal potential is as large as 2–3 cm in water height equivalent [ 2 ]. In comparison to homogeneous seawater, the total speed of a tsunami in density-stratified seawater is lower [ 3 ].…”

GEORB: Release for precise orbit determination of low Earth orbiters and satellite gravity missions

“…The orbit propagation based on numerical integration of the Equation of motion is used also to form an orbit simulation tool. The orbit simulation tool has been applied, considering a variety of gravitational forces model, to support studies of the ocean tides [31]. The current release of GEORB provides features of the precise orbit determination and the on-board accelerometer calibration modelling of the GRACE missions as demonstrated by Papanikolaou [11,12].…”