Quasi two-day-wave modulation of gravity wave flux and consequences for the planetary wave propagation in a simple circulation model

The quasi-two-day wave is forced in a simple 3-D circulation model through adding an additional heating term in the troposphere with a period of about 2 days and a zonal wavenumber 3 Hough mode structure. The model contains an updated Lindzen-type gravity wave parameterisation that allows the formation of multiple breaking levels and thus the detailed description of interaction of gravity waves, planetary waves and tides. In the presence of the two-day wave the gravity wave flux is modulated so that there appears a component with the period and horizontal structure of the planetary wave. Model results show that the quasi-two-day wave does not propagate well to the lower thermosphere. The two-day wave forced from the troposphere and the acceleration due to gravity wave breaking are out of phase in the mesosphere, which leads to damping of the two-day wave. This may suggest that, taken the model as a realistic description of the real atmosphere, the quasi-two-day wave is more likely to be forced in situ.