Erdal Yigit (George Mason University, USA) will deliver a talk on the topic "Effects of internal gravity waves from tropospheric and nontropospheric sources on the stratosphere, mesosphere and thermosphere".

Abstract:

We analyze the dynamical and thermal effects produced by internal gravity waves generated in the troposphere and above using the Coupled Middle Atmosphere Thermosphere-2 General Circulation Model (CMAT2-GCM). For this, we use the whole atmosphere nonlinear spectral gravity wave parameterization of Yigit et al. (2008) and its extension by Medvedev et al. (2023) to include non-tropospheric sources implemented in the CMAT2-GCM. We conducted systematic GCM experiments for northern summer solstice conditions, first including only tropospheric sources (i.e., just primary gravity waves), then non-tropospheric sources, including sources localized at 50 and 90 km, and uniformly distributed over all heights above the tropospheric sources. Gravity waves produce the greatest dynamical and thermal changes when the sources are distributed over all heights, compared to the localized sources. The higher in altitude the localized sources are found, the weaker are the effects of such sources in the middle and upper atmosphere. We also study the longitudinal and local time variability of primary and non-primary gravity waves. 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. Overall, the whole atmosphere gravity wave scheme, including just primary gravity waves of lower atmospheric origin capture a significant portion of the effects of gravity waves in Earth’s whole atmosphere system (Yiğit et al., 2025). Our results indicate that localized sources of gravity waves in the mesosphere are an unlikely candidate for explaining strong thermospheric signatures of observed gravity waves.