Numerical investigation of the propagation of the quasi‐two‐day wave into the lower thermosphere

Abstract

We present results of a series of numerical experiments for January conditions using a linearized spectral model which includes realistic mean winds and dissipation. These experiments were designed to characterize the propagation characteristics of the (3,0) mixed Rossby‐gravity mode through the middle atmosphere and into the lower thermosphere. Our results suggest that the wave magnitude is extremely sensitive to the zonal mean winds assumed in the calculations. In particular, our results suggest that a comparatively weak eastward stratomesospheric jet during northern hemisphere winter can account for a shift in the resonant frequency of the quasi‐two‐day wave response. Further, the inclusion of a realistic lower thermospheric jet in the summer lower thermosphere sets up a reflecting layer and an associated enhancement of the summer mesospheric wave signature. These features are in keeping with meteor and partial reflection drift radar observations.