Impact of Gravity Waves From Tropospheric and Non‐Tropospheric Sources on the Middle and Upper Atmosphere and Comparison With ICON/MIGHTI Winds

Abstract We study the dynamical and thermal roles of internal gravity waves generated in the troposphere and above using the Coupled Middle Atmosphere Thermosphere‐2 General Circulation Model. This model incorporates the whole atmosphere nonlinear spectral gravity wave parameterization and its extension to include non‐tropospheric sources. We conducted model experiments for northern summer solstice conditions, first including only tropospheric sources, then including sources localized at 50 and 90 km, and uniformly distributed over all heights. The simulated differences in mean temperature and horizontal winds demonstrate that gravity waves produce the greatest dynamical and thermal changes in the latter case compared to the localized sources. While the gravity wave drag is longitudinally uniform in the lower thermosphere, it is more localized in the upper thermosphere in all the simulations. Waves from uniformly distributed sources increase the longitudinal variability of zonal winds in the thermosphere up to 150 km. Gravity wave effects exhibit different local time variations in the lower thermosphere (100–140 km) than in the upper thermosphere. In the upper thermosphere, gravity wave effects are stronger during the day than at night. In contrast, nighttime gravity wave effects are stronger than the daytime ones in the lower thermosphere. Finally, a comparison with ICON‐MIGHTI observations shows that the model reproduces the basic structure of thermospheric winds, performing better with zonal winds than with meridional winds. Adding non‐tropospheric wave sources modifies wind structures in wave‐breaking regions, but does not improve the global statistical comparison.