Seasonal excitation of polar motion estimated from recent geophysical models and observations. Journal of Geodynamics, Elsevier, 2009, 48 (3-5) This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.Page 1 of 8A c c e p t e d M a n u s c r i p t AbstractHere we investigate the seasonal excitation balance of polar motion using recent geophysical data sets and models. Attention is focused on the contribution of the land hydrology which is expressed either by models, such as CPC, GLDAS, LaD, or by the observations provided by the experiment GRACE. Geophysical excitation series are compared to each other and to the excitation inferred from the space geodetic observations of polar motion. Comparison shows that 3 models of land hydrology considered in this work differ considerably; adding the corresponding excitation series to the combination of atmospheric and oceanic excitation data does not clearly improve agreement with observations. But combination of the GRACE-derived mass term of excitation with the motion terms of atmospheric and oceanic excitations brings the excitation balance considerably closer in case of the retrograde/prograde annual and retrograde semiannual components of polar motion. For other seasonal components as well as for the nonharmonic residuals, the estimated contributions of hydrology do not improve the excitation balance of polar motion.

No abstract

The impact of continental hydrological loading from land water, snow and ice on polar motion excitation, calculated as hydrological angular momentum (HAM), is difficult to estimate, and not as much is known about it as about atmospheric angular momentum (AAM) and oceanic angular momentum (OAM). In this paper, regional hydrological excitations to polar motion are investigated using monthly terrestrial water storage data derived from the Gravity Recovery and Climate Experiment (GRACE) mission and from the five models of land hydrology. The results show that the areas where the variance shows large variability are similar for the different models of land hydrology and for the GRACE data. Areas which have a small amplitude on the maps make an important contribution to the global hydrological excitation function of polar motion. The comparison of geodetic residuals and global hydrological excitation functions of polar motion shows that none of the hydrological excitation has enough energy to significantly improve the agreement between the observed geodetic excitation and geophysical ones.