关于章动序列计算中的地球动力学扁率的取值

ON THE VALUES OF THE EARTH DYNAMICAL FLATTENING TAKEN IN THE COMPUTATION OF NUTATION SERIES

刚体地球章动序列和非刚体地球章动的转换函数都和地球动力学扁率有关。IAU1 980章动理论中采用了一个不一致的地球动力学扁率值 ,从而影响了章动振幅的计算。本文介绍了章动序列计算中地球动力学扁率的取值。由地球模型 1 0 66A或PREM得到的地球动力学扁率值比由岁差观测得到的约小 1 % ,并且不可靠。当考虑流体静力学平衡被破坏时新的地球物理模型 ,可得到与岁差常数相一致的地球动力学扁率值。地球动力学扁率值H =0 .0 0 32 738是使用在刚体地球章动序列和章动转换函数计算中的最佳值 ,它对章动序列精度的提高作出了一定的贡献。

A rigid Earth nutation series and a non rigid Earth transfer function both are associated with the Earth dynamical flattening. The values of the Earth dynamical flattening, used in IAU 1980 nutation theory, are inconsistent, so that it products an influence on the nutation amplitude. In this paper, the values for the Earth dynamical flattening taken in the computation of nutation series are reviewed. The value of the Earth dynamical flattening derived from 1066A or PREM is too low with respect to the observed value derived from precession observation. A new theory of nutation is developed. Its Earth model accounts for violation of hydrostatic equilibrium at the initial state by incorporating mass heterogeneities as well as associated boundary displacement. The resulting Earth dynamical flattening is in agreement with the observed value. The value of the Earth dynamical flattening , H = 0.0032738, is the best value in the computations of the rigid Earth nutation series and the Earth's transfer function for nutation. The value is from the astronomical observation of equator precession. It make a contribution to an improvement of the final nutation series.