An Assessment of Recently Released High-Degree Global Geopotential Models Based on Heterogeneous Geodetic and Ocean Data

Abstract

The development of the global geopotential model (GGM) broadens its applications in ocean science, which emphasizes the importance for model assessment. We assess the recently released high-degree GGMs over the South China Sea through heterogeneous geodetic observations and synthetic/ocean reanalysis data. The comparisons with a high resolution (∼3 km) airborne gravimetric survey over the Paracel Islands show that XGM2019e_2159 has relatively high quality, where the standard deviation (SD) of the misfits against the airborne gravity data is ∼3.1 mGal. However, the comparisons with local airborne/shipborne gravity data hardly discriminate the qualities of other GGMs that have or truncated to the same expansion degree. Whereas, the comparisons with the synthetic/ocean reanalysis data demonstrate that the qualities of the values derived from different GGMs are not identical, and the ones derived from XGM2019e_2159 have better performances. The SD of the misfits between the mean dynamic topography (MDT) derived from XGM2019e_2159 and the ocean data is 2.5 cm; and this value changes to 7.1 cm/s (6.8 cm/s) when the associated zonal (meridian) geostrophic velocities are assessed. In contrast, the values derived from the other GGMs show deteriorated qualities compared to those derived from XGM2019e_2159. In particular, the contents computed from the widely used EGM2008 have relatively poor qualities, which is reduced by 3.9 cm when the MDT is assessed, and by 4.0 cm/s (5.5 cm/s) when the zonal (meridian) velocities are assessed, compared to the results derived from XGM2019e_2159. The results suggest that the choice of a GGM in oceanographic study is crucial, especially over coastal zones. Moreover, the synthetic/ocean data sets may be served as additional data sources for global/regional gravity field assessment, which are useful in regions that lack of high-quality geodetic data.

Evaluating the Impact of the Recent Combined and Satellite-Only Global Geopotential Model on the Gravimetric Geoid Model

“…Zingerle et al [16] noted that XGM2019e_2159 performs exceptionally well over oceans, showing comparable or even superior performance compared to earlier models. Furthermore, Wu et al [27] highlighted that alternative Global Geopotential Models (GGMs) exhibit reduced accuracy compared to XGM2019e_2159, with coastal zones being significantly affected. Table 1 presents data regarding the content of satellite data and the highest degree of order for the four models.…”

“…Table 1 presents data regarding the content of satellite data and the highest degree of order for the four models. Tongji-GGMG2021s 2022 300 S (Goce), S (Grace) [30] Tongji-Grace02k 2018 180 S (Grace) [30] a where A is for altimetry, S is for satellite (e.g., GRACE, GOCE, LAGEOS), G is for ground data (e.g. terrestrial.…”

An Improved Method to Moho Depth Recovery From Gravity Disturbance and Its Application in the South China Sea

“…Y. Wu et al (2021) estimated the standard deviation of XGM2019e_2159 using airborne gravity data in the Xisha Islands to be around 3.1 mGal. To begin, the free-air gravity disturbance was subtracted from low-degree spherical harmonics up to degree of 21 to eliminate the effect of mantle and deep Earth inhomogeneities (Bagherbandi & Sjöberg, 2012), as illustrated in Figure 9a.…”

Local Enhancement of Marine Gravity Field over the Spratly Islands by Combining Satellite SAR Altimeter-Derived Gravity Data

“…A satellite-only GGM, namely, GOCO06S, was used to represent the longwavelength component of XGM2019e_2159, and the gravimetric data sources from National Geospatial-Intelligence Agency (NGA) and DTU13GRA were used to compute the shortwavelength component of this model [46]. The validation against local airborne gravimetric observations demonstrated that XGM2019e_2159 had improved precision, by a magnitude of ~1 mGal, compared to the GGMs that have similar expansion degrees [47].…”