Articles | Volume 15, issue 9
Ann. Geophys., 15, 1176–1186, 1997

Special issue: Wind Measurements

Ann. Geophys., 15, 1176–1186, 1997

  30 Sep 1997

30 Sep 1997

Diurnal tidal variability in the upper mesosphere and lower thermosphere

M. E. Hagan1, C. McLandress2, and J. M. Forbes3 M. E. Hagan et al.
  • 1National Center for Atmospheric Research, High Altitude Observatory, Boulder, Colorado, USA
  • 2Institute for Space and Terrestrial Science, North York, Ontario, Canada
  • 3Department of Aerospace Engineering Sciences, University of Colorado, Boulder, USA

Abstract. We explore tropospheric latent heat release as a source of variability of the diurnal tide in the mesosphere and lower thermosphere (MLT) in two ways. First, we present analyses of the UARS WINDII horizontal wind data, which reveal signatures of nonmigrating tidal effects as large as 25 m/s during both vernal equinox and boreal winter. These effects are of greater relative importance during the latter season. Complementary global-scale wave model (GSWM) results which account for a tropospheric latent heat source generally underestimate the observed nonmigrating tidal effects but capture the seasonal variability that is observed. Second, we pursue a new parameterization scheme to investigate seasonal variability of the migrating diurnal tidal component of the latent heat source with GSWM. These results confirm previously reported seasonal trends, but suggest that the MLT effects may be as much as an order of magnitude larger than earlier predictions.

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