Comparison of Earth-tide parameters over a large latitude difference

Abstract

Gravity Earth-tide observations at the station of Thessaloniki with a LaCoste-Romberg gravity meter equipped with electrostatic feedback were analysed in order to obtain accurate amplitude and phase-difference tidal parameters. The observations cover a total number of 162.5 days. The frequency transfer-function of our measuring system was defined using the step-response procedure. The Tamura tidal development was used as normal tidal potential. A standard deviation of the weight unit equal to 7.007 nm s-2 resulted from the adjustment procedure before the correction due to barometric pressure changes. Taking into account the barometric pressure changes trough a linear regression model this standard deviation dropped to 6.821 nm s-2, showing that these changes only slightly affect the observations. The computed amplitude factors and phase differences for O1 and M2 were compared with corresponding parameters from stations distributed over a large latitude difference, in order to study the latitude dependence of the gravimetric body tide factors. The comparison showed that in South Europe the tidal parameters fit, with some local discrepancies, to other stations in Central Europe after correction for ocean load.