A new nutation model of a non-rigid earth with ocean and atmosphere

Abstract

By integrating the truncated complex scalar gravitational motion equations for an anelastic, rotating, slightly elliptical earth, the complex frequency-dependent earth transfer functions are computed directly. Unlike the conventional method, the contributions of both oceanic load and current to all nutation periods, as well as the atmospheric contributions to prograde annual, retrograde annual and retrograde semi-annual nutation, are included in the integration via outer surface boundary conditions, all of which are expanded to second order in ellipticity. A modified ellipticity profile of second-order accuracy for the non-hydrostatic earth is obtained from Clairaut's equation and the PREM earth model by adjusting both the ellipticity of the core-mantle boundary and the global dynamical ellipticity to modern observations. The effects of different earth models, anelastic models and ocean models are computed and compared. Finally, a complete new nutation series of 343 periods, including in-phase and out-of-phase parts of longitude and obliquity terms, for a more realistic earth is obtained and compared with other available nutation series and observations.