A study of the observed tidal residue vectors B versus oceanic tidal load vectors L

The Earth Tides Data Bank holds the results of more than three hundred tidal gravity stations. Fifty percent of them are directly connected to the ICET (International Center for Earth Tides) network and outside of Europe it is ninety percent of them. The correlation between the tidal loading vector L computed from Schwiderski maps and the tidal residual vector B deduced from these observations by computing the linear regression of the in phase and the out of phase components is studied. If the coastal stations (D less than or equal to 5 km) are discarded, the slopes of the regression lines are equal to unity except for the sine components in Europe where the observed effect is 5% larger than the computed one. A phase lag of the body tides is observed: the independent term is not significantly different from zero for the cosine components while, for the sine components, and for any combination of stations, it takes negative values comprised between -0.200 and -0.300 which corresponds to a phase lag of -0.4 deg. This value is in agreement with the evaluation by Schwiderski of the effect of the pressure of the oceanic tides on the tidally deformed bottom of the ocean.