Influence of Atmosphere and Zonal Tides on High-Frequency Variation of Length of Day

In this paper the atmospheric contribution to high-frequency variation of the earth rotation is studied with the series of LOD (EOP (IERS)99 C04))and axial component of the atmospheric angular momentum (AAM)supplied by International Earth Rotation Service (IERS) and U.S.National Centers for Environmental Prediction (NCEP ), by which the past meteorological data were re -analyzed and computed, respectively.The spectral peaks of 9.13,13.66, 13.63,13.66,27.55 days, which have large ratio of signal to noise, exist in the LOD series and the significant level of these spectral term is greater than 90 % by using the Multitaper power spectrum method.From the results of spectral analysis on difference between AAM and LOD, and estimation of the Earth s zonal response coefficient k,it is found that the atmosphere is not the main excitation source for high-frequency variation of the Earth Rotation, but the main contribution is from ocean tides based on the theoretical tidal periods.