Effects of Non-Classical Gravity-Wave Dynamics on Middle-Atmosphere Circulation and Solar Tides

Mostly for reasons of efficiency, the standard approach to parameterizing gravity wave leaves out various effects. Among others, two of those are oblique wave propagation and horizontal flux convergences, summarized as 3D effects. Another aspect is deviations of wave-mean-flow interaction that arise if the mean flow is not balanced, so that pseudo-momentum (Eliassen-Palm) fluxes do not suffice for the quantification of the wave impact on the resolved flow (Wei et al 2019). The comparative importance of these effects for zonal-mean winds and temperatures, residual-mean transport, and solar tides has been investigated, using the Lagrangian gravity-wave parameterization MS-GWaM (Bölöni et al 2021, Kim et al 2021, 2024, Voelker et al 2024) in the global circulation model ICON. Comparisons between ensembles of boreal-winter simulations show that 3D dynamics leads to a statistically significant relative circulation that lowers and cools the summer mesopause but also cools/heats the summer/winter stratopause region and cools the mid-latitude winter stratosphere. Replacing pseudo-momentum forcing by a more general approach mainly affects in December the summer mesopause in manner opposite to 3D, and in February also reduces significantly the polar-night jet in the stratosphere. Gravity waves seem to be responsible for most of the differences, but modified Rossby-wave fluxes partly compensate for their effects, in a manner similar as observed by Cohen et al (2013). Solar tides show a related response, where non-balanced dynamics mostly affects the summer mesosphere / lower thermosphere, but 3D has significant effects on tides in both hemispheres and down into the stratosphere.