Using real polar ground gravimetry data to solve the GOCE polar gap problem in satellite-only gravity field recovery

Abstract

With the successful completion of European Space Agency (ESA)'s PolarGAP campaign, ground gravity data are now available for both polar regions. Therefore, it is now possible to solve the GOCE polar gap problem in satellite-only gravity field recovery by using additional polar ground gravity data instead of some regularization methods. However, ground gravimetry data need to be filtered to remove the short-wavelength information beyond a certain harmonic degree to avoid spectral leakage when inferring satellite-only gravity field models. For the Arctic, the ArcGP data set was successfully applied when inferring the high-resolution gravity field model EGM2008 which could be used for this filtering there. For Antarctica, a combination of latest airborne gravimetry data from ESA's PolarGap campaign and some previous gravity data was recently published which was irregularly distributed in space and still had some small gaps within the GOCE south polar gap. Therefore, we proposed a point mass modeling method for this filtering which was similar to the way using EGM2008 for such filtering to the ground gravity data in the Arctic. Furthermore, a variance component estimation was applied to combine the normal equations from the different sources to build a global gravity field model called IGGT_R1C. Then, this model's accuracy was evaluated by comparison with other gravity field models in terms of difference degree amplitudes, gravity anomaly differences as well as external checking by obit adjustment and gravity data in the GOCE polar gap areas. This gravity field model performed well globally according to these checking results; especially, the RMS of the residuals between the filtered gravity data and that calculated from IGGT_R1C was the smallest (2.6 mGal in the Arctic and 5.4 mGal in Antarctica) compared with that of the relevant satellite-only gravity field models, e.g., GOCO05s. Therefore, the disturbing impact of the GOCE polar data gap problem could be solved by adding the polar ground gravity data.

An Improved Model of the Earth’s Static Gravity Field Solely Derived from Reprocessed GOCE Data

“…Various kinds of prior information are possible, e.g., additional data sources from GRACE (e.g., Bruinsma et al 2014) or terrestrial campaigns (e.g., Zingerle et al 2019b;Lu et al 2020). To remain independent of other gravity field data, the time-wise modeling applies simple mathematical smoothness conditions to force the full signal toward zero using regularization.…”

A parallel numerical algorithm by combining MPI and OpenMP programming models with applications in gravity field recovery

“…The IGGT_R1C is better than GOCO01S due to the contribution of more GRACE observations (ITSG-Grace2014s compared to ITG-Grace2010s) and the polar gravity anomalies (Mayer-Gürr et al, 2010;Pail et al, 2010). Additional GNSS/leveling checking and gravimetry data checking could be found in the former publications (Lu et al, 2018b;Lu et al, 2020).…”

“…Therefore, it has limitations to use MPI programming models between nodes. In this context, we studied a parallel numerical algorithm based on MPI and OpenMP programming models to speed up the calculation progress on small HPC clusters for global and regional gravity field recovery [e.g., IGGT_R1, IGGT_R1C, HUST-Grace2016, HUST-Grace2016s (Lu et al, 2017a;Zhou et al, 2017a;Lu et al, 2017b;Zhou et al, 2017b;Lu et al, 2018b;Zhou et al, 2018;Lu et al, 2020)]. Specifically, MPI is used for inter-node communication, and OpenMP is used for intra-node communication (Pacheco, 1997;Gropp et al, 1999).…”

Marine Gravimetry and Its Improvements to Seafloor Topography Estimation in the Southwestern Coastal Area of the Baltic Sea

“…Here, the uniformed vertical datum could also be transformed to the geoid derived from the latest gravity field models, e.g., EIGEN-6C4 or future uniformed local geoid in the Baltic Sea area, which contain the latest satellite gravimetry data from the Gravity Recovery And Climate Experiment (GRACE), Gravity field and steady-state Ocean Circulation Explorer (GOCE), as well as GRACE-FO (e.g., [59][60][61][62][63][64][65]). For example, the RMS of geoid differences between EIGEN-6C4 and EGM2008 is 3 cm in this study area.…”