Validation of recently released GOCE-based satellite-only global geopotential models over the Red Sea using shipborne gravity data

The gravity fi eld and steady-state ocean circulation explorer (GOCE) satellite,
successfully concluded its mission in October 2013 after collecting unprecedented
gravity gradient measurements. Such GOCE data made it possible to improve the
determination of the geoid over the Red Sea region. The performance of GOCE-based
satellite-only global geopotential models (GGMs), at the end of its mission, is evaluated
via spectral analysis and by using shipborne free-air gravity anomalies collected over
the study area, namely the Red Sea. Eight of the most recent GOCE-based satelliteonly
GGMs, namely the DIR_R5, ITU_GGC16_2, SPW_R5, TIM_R5, NULP_02S,
IfE_GOCE05s, IGGT_R1, and GGM05G, are validated. Firstly, the spectral analysis of
these GGMs was performed. The DIR_R5 model showed a superior behaviour, in all
terms, in comparison to all the investigated GGMs. Then, the GGMs were evaluated,
from spherical harmonics degree/order (d/o) ranging from 100 to their maximum d/o,
with respect to the shipborne gravity data after applying the spectral enhancement
method, to overcome the existing spectral gap. All the studied GGMs closely calculated
the full power of gravity anomaly at a spherical harmonic d/o equivalent to 160.
Regardless of the cross-comparable results obtained by the DIR_R5, TIM_R5, SPW_
R5, ITU_GGC16_2, and IfE_GOCE05s, whose standard deviation (STD) values of the
differences with respect to shipborne data range from 9.90 and 9.93 mGal, the SPW_
R5 model produced the best results with discrepancies characterised with a minimum,
maximum, mean, and STD of -56.26, 131.29, 2.07, and 9.90 mGal, respectively.