Gravity anomalies determined from mean sea surface model data over the Gulf of Mexico

With the improvements in the density and quality of satellite altimetry data,a high-precision and high-resolution mean sea surface model containing abundant information regarding a marine gravity field can be calculated from long-time series multi-satellite altimeter data.Therefore,in this study,a method was proposed for determining marine gravity anomalies from a mean sea surface model.Taking the Gulf of Mexico(15°–32°N,80°–100°W)as the study area and using a removal-recovery method,the residual gridded deflections of the vertical(DOVs)are calculated by combining the mean sea surface,mean dynamic topography,and XGM2019e_2159 geoid,and then using the inverse Vening-Meinesz method to determine the residual marine gravity anomalies from the residual gridded DOVs.Finally,residual gravity anomalies are added to the XGM2019e_2159 gravity anomalies to derive marine gravity anomaly models.In this study,the marine gravity anomalies were estimated with mean sea surface models CNES_CLS15MSS,DTU21MSS,and SDUST2020MSS and the mean dynamic topography models CNES_CLS18MDT and DTU22MDT.The accuracy of the marine gravity anomalies derived by the mean sea surface model was assessed based on ship-borne gravity data.The results show that the difference between the gravity anomalies derived by DTU21MSS and CNES_CLS18MDT and those of the ship-borne gravity data is optimal.With an increase in the distance from the coast,the difference between the gravity anomalies derived by mean sea surface models and ship-borne gravity data gradually decreases.The accuracy of the difference between the gravity anomalies derived by mean sea surface models and those from ship-borne gravity data are optimal at a depth of 3–4 km.The accuracy of the gravity anomalies derived by the mean sea surface model is high.

Lunar deflections of the vertical and their distribution

The deflection of the vertical reflects the mass distribution and density anomaly of celestial bodies. Lunar deflections of the vertical include directional information of the Moon’s gravity field. SGM90d, recovered from SELENE mission, revealed the lunar far side gravity field for the first time in history owes to 4-way Doppler data. Lunar deflections of the vertical and their meridional and prime vertical components are calculated from SGM90d, and then their global distributions are also given in the paper. The gradients of lunar deflections of the vertical are defined and computed as well. The correlations between the lunar deflections of the vertical and the lunar terrain have been fully discussed. Many different characteristics of lunar deflections of vertical have been found between the near side and the far side of the Moon, which may be caused from the lithospheric compensation and the uplifting of mantle.

Calibration for GOCE Gradiometer Data Based on the Prior Gravity Models

The determination of the calibration parameters of the gravity gradiometer play an important role in the GOCE gravity gradient data processing.In this paper,the temporal signals and outliers in the GOCE gravity gradient observations are analyzed.Based on the different global gravity field models,the scale factors and biases are determined in all the components of GOCE gravity gradients.And then the accuracy of the calibration results is validated.The results indicated that the effect of the ocean tide is at mE magnitude in the measurement band,which is equivalent to the precision of the gravity gradiometer,while the effect of the non-tide temporal signals,such as terrestrial water is in the order of 10-4 E,is slightly less than that of the ocean tide.The outliers in all the gravity gradient components are larger than 0.2%.And after the calibration using global gravity field models except EGM96,the stability of scale factors in the V xx、V yy、V zz、V yz components reaches 10-4 magnitude,and the V xz component reaches 10-5 while that of the V xy component is about 10-2,which are in accordance with the accuracy differences of the gradient components.