Amplitude spectra of the low degree gravity field

Many representations of the earth's gravitational field have been obtained in recent years, The coefficients in the spherical harmonics expansion of the geopotential derived by various researchers are slowly beginning to converge, at least for those of degree 4 and lower. Comparison of the coefficients themselves does not leave one with a very intuitive feeling for the actual differences between representations. In this letter, we shall compare several recently derived representations in terms of the amplitude spectra of each degree in a spherical harmonics expansion.