Consequences of the Superposition of Tidal Components on the Dynamics of the Mesosphere and Lower Thermosphere

Abstract:

It is now generally accepted that the superposition of tidal components results in geographic variations in their observed amplitudes in the mesosphere and lower thermosphere (MLT). This superposition also has implications for the dynamical and convective stability of the atmosphere at these heights. Spatial variations in the amplitude of the temperature and vertical displacement also have consequences for chemistry and chemical heating in this region. In this paper, these superposition effects are explored using diagnosed fields from the extended Canadian Middle Atmosphere Model and CMAM30. The nature and distribution of wind and temperature variability, the associated instabilities and chemical heating are discussed. Superposition effects have consequences for tidal dissipation and gravity wave propagation in the MLT. They also may be a cause for some of the inversion layers observed in this region of the atmosphere.