Atmospheric excitation of the Earth's nutation: Comparison of different atmospheric models

[1] Using the angular momentum approach, the effect of the atmosphere on the Earth's nutation is evaluated from five atmospheric circulation models. Five nutation frequencies are considered: the annual and semiannual prograde and retrograde and the terannual prograde. The atmospheric effect on the 18.6-year nutation is also evaluated from the only model that gives a long enough homogeneous series. The results obtained from the different models and a noninverted barometer ocean model are intercompared and compared with the residuals between the observed and computed nutations. The evaluation of the atmospheric effect on the Earth's nutation is shown to be above the observation precision, particularly at the annual frequency (prograde and retrograde) and the semiannual prograde frequency but is highly dependent on the model used, strengthening the importance of having a correct estimation for the atmospheric effects on nutation. The time evolution of the atmospheric excitation of the nutation is also studied, using a wavelet analysis and a sliding-window least squares method. We show that the fluctuations of the excited amplitude are above the level of precision of the observation.