Effect of the Earth’s triaxiality on the tide-generating potential

Abstract

Latest harmonic developments of the Earth tide-generating potential (TGP), e.g., HW95 (Hartmann and Wenzel in Geoph Res Lett 22:3553, 1995), RATGP95 (Roosbeek in Geophys J Int 126:197, 1996), KSM03 (Kudryavtsev in J Geodesy 77:829, 2004), include a number of terms caused by the joint effect of the Earth’s polar flattening (that can be numerically described by the \({J}_{2}\) geopotential coefficient) and the Moon/the Sun gravitational attraction. In the present study, we additionally consider the effect of the Earth’s equatorial flattening due to the Earth’s triaxiality. Explicit analytical expressions for the relevant part of the TGP are derived. New terms of the TGP development due to the Earth’s triaxial figure are found. Amplitudes of nineteen of them exceed the threshold level of 10^–8 m²s⁻² used by the modern tidal potential catalogs. Three of the new terms have the frequency sign opposite to that of the Earth rotation. It is not the case for any previously known term of the Earth TGP development. Every term has a new feature that an integer multiplier of the mean local lunar time used in its argument is not equal to the order of the spherical harmonic associated with the term. It necessitates a relevant modification of the standard HW95 format for representing the Earth TGP. The new terms are suggested for including in the current and future tidal potential catalogs.