ON THE RECOVERY OF TEMPORAL VARIATIONS OF GEOID HEIGHTS DETERMINED WITH THE USE OF GGMS BASED ON SST-HL DATA FROM NON-DEDICATED GRAVITY SATELLITE MISSIONS

Walyeldeen Godah,Malgorzata Szelachowska,Jan Krynski

doi:10.1590/s1982-21702019000300017

Abstract

Abstract Over 15 years the Gravity Recovery and Climate Experiment (GRACE) had considerably contributed to the determination of temporal variations of geoid heights. In May 2018, GRACE Follow-On (GRACE-FO) was launched. The aim of this contribution is to assess the suitability of data from non-dedicated gravity satellite missions (N-DGSMs) for the determination of temporal variations of geoid heights and bridging the gap between GRACE and GRACE-FO. The Amazon basin and the area of Poland were chosen as study areas. Monthly Global Geopotential Models (GGMs) developed using N-DGSMs data were utilized to determine temporal variations of geoid heights over the chosen study areas. Then, the obtained temporal variations of geoid heights were evaluated using ITSG-GRACE2016 GGMs. Time series of geoid height variations determined from GGMs of some N-DGSMs were smoothed using a moving average. The main findings reveal that for areas characterized with strong mass transport, e.g. the Amazon basin, correlation coefficients between smoothed temporal variations of geoid heights from GGMs of some N-DGSMs and temporal variations of geoid heights from the ITSG-GRACE2016 GGMs reach the level of 0.6. For areas with a weak mass transport signal as for Poland, N-DGSMs-based GGMs investigated seem unsuitable for determining temporal variations of geoid heights.

Highlights

A precise geoid is essentially needed for the realization of the vertical reference system
The suitability of GGMs developed with the use of SST-hl data from non-dedicated gravity satellite missions (N-DGSM) for recovering temporal variations of geoid heights ∆N and filling the gap between Gravity Recovery and Climate Experiment (GRACE) and GRACE-FO was investigated at two test areas, i.e. the Amazon basin and the area of Poland, characterized with substantially different amplitudes of seasonal variations of geoid heights
The ∆N obtained from ITSG-GRACE2016 GGMs, that cover the period April 2002–June 2017, were validated with the respective ones obtained from CSR RL05 GGMs

Summary

Introduction

A precise geoid is essentially needed for the realization of the vertical reference system. It serves as a reference surface for the transformation between the geometrical ellipsoidal height obtained from Global Navigation Satellite System (GNSS) measurements and gravity-based heights, e.g. orthometric and normal heights, determined with the use of spirit levelling (cf Torge and Müller 2012). It is required in many Earth’s science disciplines. E.g. Rangelova (2007), Rangelova and Sideris (2008), Rangelova et al (2010), Krynski et al (2014) and Godah et al (2017, 2018), reveled the importance of temporal variations of geoid heights for high accuracy regional geoid modelling that has been considered as one of the activities of the Joint Study Group 0.15 (JSG 0.15) of the Commission 2 – Gravity Field of the International Association of Geodesy (IAG) (see Drewes et al 2016)

Methods

Results

Conclusion