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Atmospheric angular momentum related to Earth rotation studies: history and modern developments / David A. Salstein (2019) 

Public Titre : Atmospheric angular momentum related to Earth rotation studies: history and modern developments Type de document : Article/Communication Auteurs : David A. Salstein, Auteur Editeur : Paris, Meudon et Nançay : Observatoire de Paris Année de publication : 2019 Conférence : JSRST 2019, Journées systèmes de référence spatio-temporels, Astrometry, Earth Rotation, and Reference Systems in the GAIA era 07/10/2019 09/10/2019 Paris France OA Proceedings Importance : pp 209 - 213 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie [Termes IGN] moment cinétique atmosphérique [Termes IGN] rotation de la Terre Résumé : (auteur) It was noted some time ago that the angular momentum of the atmosphere varies, both regionally as well as in total. Given the conservation of angular momentum in the Earth system, except for known external torques, such variability implies transfer of the angular momentum across the atmosphere’s lower boundary. As nearly all is absorbed by the Earth below, the solid Earth changes its overall rotation from this impact. Due to the large difference between in the moments of inertia of the atmosphere and Earth, relatively big differences in the atmosphere are translated as relatively very small differences in the Earth, measurable as changes in Earth rotation rate, and polar motion. The atmospheric angular momentum (AAM) is that due to the motion of the winds and to the changes in mass distribution, closely related to the atmosphere pressure patterns; its variability in the atmosphere is mirrored in the Earth rotation rate and polar motion. This connection between the global solid Earth properties and the global and regional atmosphere on a number of time scales, especially seasonal and interannual, was much appreciated by Barbara Kolaczek, with Jolanta Nastula, at the Space Research Center in Warsaw, and this was a subject of our collaborative studies. Many calculations were made of atmospheric angular momentum, leading to a service under the Global Geophysical Fluids Center of the IERS based on calculations using both operational meteorological series, determined for weather forecasting purposes, and retrospective analyses of the atmosphere. Theoretical development of the connection between the AAM, Earth rotation/polar motion, and also the angular momentum of the other geophysical fluids occurred at the same time that space-based observations and enhanced computer power were allowing improved skills for both weather analysis and forecasting. Hence better determination of the AAM became possible, which could be used as a measure for forecasting Earth rotation. Today we are looking at the atmosphere in combination with the ocean and other fluids, and also assessing the implications of climate variability on Earth rotation through climate model research. According to models of the Earth system, significant changes in winds appear to be a possible result of climate change, with implications for the Earth rotation parameters. Numéro de notice : C2019-076 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Communication DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=100193

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