HR: 09:15h
AN: G31A-06    [Abstracts]
TI: Operational numerical simulations of short-term atmospheric and oceanic induced variations of Earth's rotation and coordinates of the geocenter
AU: * Thomas, M
EM: mthom@rcs.urz.tu-dresden.de
AF: Dresden University of Technology Institute for Planetary Geodesy, Lohrmann Observatory, Dresden, 01062 Germany
AU: Dobslaw, H
EM: henryk.dobslaw@tu-dresden.de
AF: Dresden University of Technology Institute for Planetary Geodesy, Lohrmann Observatory, Dresden, 01062 Germany
AB: Circulation and tidal induced mass redistributions in the atmosphere-ocean system affect the Earth's rotational parameters and the geocenter on timescales from hours to decades. While seasonal to interannual signals in atmosphere and oceans are mainly attributed to the general circulation, subdaily to fortnightly mass redistributions are dominated by gravitational as well as pressure induced tidal effects. In contrast to the oceans, gravitational tides in the atmosphere can almost be neglected, but pressure variations principally caused by the combined effects of sunlight absorption of water vapor and ozone heating can be observed down to the Earth's surface, which cause in turn additional oceanic tides due to pressure loading. Since atmospheric conditions are typically described by 6-hourly analysis fields, semidiurnal pressure variations cannot be properly resolved. Therefore, ECMWF's 3-hourly short-range forecasts are combined with corresponding analyses to describe atmospheric variability down to subdiurnal timescales. The resulting atmospheric fields are used as forcing conditions for simulations with the Ocean Model for Circulation and Tides (OMCT) in order to estimate the oceanic response and, thus, short-term mass redistributions in the atmosphere-ocean system and corresponding influences on nutation, polar motion, length-of-day, and coordinates of the geocenter. Since operational atmospheric data are available within a few days only, atmospheric and oceanic mass variations as presented here can be provided on an operational basis relevant, e.g., for high-resolution Earth rotation parameters and a separation of gravitationally and pressure induced oceanic tides.
DE: 1239 Earth rotation variations
SC: Geodesy [G]
MN: Fall Meeting 2005