Nonmigrating tides in equinox temperature fields from the Extended Canadian Middle Atmosphere Model (CMAM)

Abstract

The extended Canadian Middle Atmosphere model has been analyzed for wave 0, 1 and wave 2 temperature signatures associated with diurnal and semidiurnal migrating and nonmigrating tides. These waves are ubiquitous in the model data and have significant amplitudes relative to the migrating diurnal tide. They are formed both by forcing in the troposphere and through nonlinear interaction in the middle atmosphere. Superposition of the tidal signatures results in significant longitudinal variations in the local derived diurnal and semidiurnal amplitudes and localized regions of convective instability which may be a source for the inversion layers observed in the mesosphere and the bores seen in airglow data. It is conjectured that the dissipation of tidal components can only be understood when they are considered as a system and not as individual components. The superposed tidal fields have a strong geographic dependence. Associated airglow signatures and chemistry will exhibit similar variability. Copyright 2005 by the American Geophysical Union.