Comparisons Between TIME-GCM/MERRA Simulations and LEO Satellite Observations

Kathrin Haeusler, NCAR / HAO, Boulder, CO, United States, Maura E Hagan, National Center for Atmospheric Research, Boulder, CO, United States, Jeffrey M M Forbes, University of Colorado at Boulder, Ann and H.J. Smead Department of Aerospace Engineering Sciences, Boulder, United States, Xiaoli Zhang, University of Colorado at Boulder, Boulder, CO, United States, Eelco Doornbos, Royal Netherlands Meteorological Institute, Aerospace Engineering, De Bilt, Netherlands, Sean Bruinsma, CNES French National Center for Space Studies, Toulouse Cedex 09, France and Gang Lu, National Center for Atmospheric Research, High Altitude Observatory, Boulder, CO, United States
Abstract:
We report on yearlong National Center for Atmospheric Research (NCAR) thermosphere-ionosphere-mesosphere-electrodynamics general circulation model (TIME-GCM) simulations where we utilize the recently developed lower boundary condition based on 3-hourly MERRA (Modern-Era Retrospective Analysis for Research and Application) reanalysis data to account for tropospheric waves and tides propagating upward into the model domain. The solar and geomagnetic forcing is based on prevailing geophysical conditions. The simulations show a strong day-to-day variability in the upper thermospheric neutral temperature tidal fields, which is smoothed out quickly when averaging is applied over several days, e.g. up to 50% DE3 amplitude reduction for a 10-day average. This is an important result with respect to tidal diagnostics from satellite observations where averaging over multiple days is inevitable. In order to assess TIME-GCM performance we compare the simulations with measurements from the Gravity field and steady-state Ocean Circulation Explorer (GOCE), Challenging Minisatellite Payload (CHAMP) and Gravity Recovery and Climate Experiment (GRACE) satellites.
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