NUMERICAL INVESTIGATION OF THE PROPAGATION OF THE QUASI-2-DAY WAVE INTO THE LOWER THERMOSPHERE

We present results of a series of numerical experiments for January co nditions using a linearized spectral model which includes realistic me an winds and dissipation. These experiments were designed to character ize the propagation characteristics of the (3,0) mixed Rossby-gravity mode through the middle atmosphere and into the lower thermosphere. Ou r results suggest that the wave magnitude is extremely sensitive to th e zonal mean winds assumed in the calculations. In particular, our res ults suggest that a comparatively weak eastward stratomesospheric jet during northern hemisphere winter can account for a shift in the reson ant frequency of the quasi-two-day wave,response. Further, the inclusi on of a realistic lower thermospheric jet in the summer lower thermosp here sets up a reflecting layer and an associated enhancement of the s ummer mesospheric wave signature. These features are in keeping with m eteor and partial reflection drift radar observations.