Extending the Parameterization of Gravity Waves into the Thermosphere and Modeling Their Effects

Abstract

Vertical coupling by gravity waves (GWs) between the lower atmosphere and thermosphere is studied with a general circulation model (GCM) extending from the tropopause to the upper atmosphere. A newly developed nonlinear spectral GW parameterization, which accounts for wave propagation in the highly dissipative thermosphere, has been implemented into the Coupled Middle Atmosphere-Thermosphere-2 (CMAT2) GCM. In addition to the nonlinear saturation, the extended scheme considers wave dissipation suitable for the thermosphere-ionosphere, such as molecular viscosity and thermal conduction, ion drag, eddy diffusivity, and radiative damping. The results of simulations for June solstice show that the dynamical and thermal effects of GWs are strong and cannot be neglected in the thermosphere. At F region heights, GW momentum deposition is comparable to the ion drag and GW-induced heating/cooling competes with the high-latitude Joule heating.