Atmospheric excitation of Earth rotation/polar motion at high temporal resolution

Author: David Salstein and Katherine J. Quinn
September 17, 2007 - September 19, 2007
Journal Article
Proceedings Journées Systèmes de Référence Spatio-temporels

Salstein D.A., Nastula J., Quinn K., MacMillan D., Mendes Cerveira, P.J. 2007: Atmospheric excitation of Earth rotation/polar motion at high temporal resolution, Proceedings,“Journées Systèmes de Référence Spatio-temporels,” 177-179, Paris Observatory, Paris, France.

We have calculated atmospheric effective angular momentum functions of Earth ro- tation/polar motion with hourly resolution based on the NASA Goddard Earth Observation System (GEOS-4) atmospheric model. Such excitations are based on model forecasts at five of the six hours, and a mixture of model and observations at the sixth hour. This heterogeneous procedure can cause discontinuities if not mitigated by special approaches. The wind-based polar motion terms have a strong diurnal signal related to tidal fluctuations, though the phase appears to vacillate. October 2002 en- compassing the intensive CONT02 Earth rotation-observing period was selected here. Time-spectra of wind-based, pressure-based, and geodetic terms reveal diurnal and semidiurnal signals with additional ´ sub-daily spectral peaks. NASA is currently introducing the d2Modern Era Retrospective-Analysis Re- search and Applications system, which should eliminate the 6-hour discontinuities. This MERRA system will give us the opportunity to investigate high temporal resolution excitation for more recent CONT campaigns.