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Interprétation géophysique du mouvement du pôle : Apport des observations de géodésie spatiale, de météorologie, d'océanographie et d'hydrologie

Abstract : The polar motion excitation is mainly due to the mass transport of the atmosphere and the oceans. So far, the observed motion is not fully explained from seasonal to diurnal scales. Our effort has focused on the Chandler wobble as well as fluctuations with period smaller than 50 days and diurnal variations, which remain still partially unexplained. We show that the atmospheric and oceanic mass redistributions are the principal causes of the Chandler wobble irregularities and the rapid polar motion of periods between 3 and 50 days. However, major differences persist at diurnal scales. Moreover, the redistributions of the continental water are important but, modelling those processes is imprecise due to the complexity and lack of observations of terrestrial hydrology. Current models must be then validated and compared to the observed polar motion. We show that the hydrological models, coupled with oceanic and atmospheric effects, improve the seasonal and long term mass balance. Thanks to space mission Gravity Discovery and Climate Experiment (GRACE), the total mass redistribution on the Earth can be determined with a different approach. Four analysis centers provide temporal variations of spherical harmonics C20, C21 and S21 of the gravity field that are proportional to the length of day and polar motion excitations caused by surface mass changes. We have analized the latest updates of these series. Despite a significant level of noise, their hydrological residual matches reasonably well the observed polar motion.
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https://tel.archives-ouvertes.fr/tel-01958536
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Lucía Seoane Corral. Interprétation géophysique du mouvement du pôle : Apport des observations de géodésie spatiale, de météorologie, d'océanographie et d'hydrologie. Astrophysique [astro-ph]. Observatoire de Paris, 2010. Français. ⟨tel-01958536⟩

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