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The dynamical and thermodynamical importance of gravity waves was initially recognized in the atmosphere of Earth. Extensive studies over recent decades demonstrated that gravity waves exist in atmospheres of other planets, similarly play a significant role in the vertical coupling of atmospheric layers and, thus, must be included in numerical general circulation models. Since the spatial scales of gravity waves are smaller than the typical spatial resolution of most models, atmospheric forcing produced by them must be parameterized. This paper presents a review of gravity waves in planetary atmospheres, outlines their main characteristics and forcing mechanisms, and summarizes approaches to capturing gravity wave effects in numerical models. The main goal of this review is to bridge research communities studying atmospheres of Earth and other planets.

For the first time, gravity wave‐induced heating and cooling effects were fully and interactively incorporated into a Martian general circulation model (GCM). Simulations with a comprehensive GCM with an implemented spectral nonlinear gravity wave (GW) parameterization revealed significant thermal effects of GWs in the mesosphere and lower thermosphere (MLT) between 100 and 150 km. Wave‐induced heating and cooling rates are comparable with those due to near‐IR CO2 heating and IR CO2cooling, correspondingly. Accounting for thermal effects of GWs results in a colder simulated MLT, with the most of cooling taking place in middle‐ and high‐latitudes. In the winter hemisphere, the temperature decrease can exceed 45 K. The colder simulated MLT is in a good agreement with the SPICAM stellar occultation measurements and Mars Odyssey aerobraking temperature retrievals. Our experiments suggest that thermal effects of GWs are probably a key physical mechanism in the MLT missing in contemporary Martian GCMs. Key Points Thermal effects of GWs have been parameterized in a Martian GCM GWs produce a significant cooling above 100 km, well in line with observations These effects are comparable with radiative effects of CO2 and must be accounted

Our recently developed nonlinear spectral gravity wave (GW) parameterization has been implemented into a Martian general circulation model (GCM) that has been extended to ∼130 km height. The simulations reveal a very strong influence of subgrid‐scale GWs with non‐zero phase velocities in the upper mesosphere (100–130 km). The momentum deposition provided by breaking/saturating/dissipating GWs of lower atmospheric origin significantly decelerate the zonal wind, and even produce jet reversals similar to those observed in the terrestrial mesosphere and lower thermosphere. GWs also weaken the meridional wind, transform the two‐cell meridional equinoctial circulation to a one‐cell summer‐to‐winter hemisphere transport, and modify the zonal‐mean temperature by up to ±15 K. Especially large temperature changes occur over the winter pole, where GW‐altered meridional circulation enhances both “middle” and “upper” atmosphere maxima by up to 25 K. A series of sensitivity tests demonstrates that these results are not an artefact of a poorly constrained GW scheme, but must be considered as robust features of the Martian atmospheric dynamics. Key Points Spectral gravity wave parameterization was introduced into a Martian GCM GW turn out to be extremely important in the Martian atmosphere Their dynamical effects are similar to those in the terrestrial mesosphere

Simulations with the Saturn Thermosphere‐Ionosphere General Circulation Model have revealed global‐scale gravity waves in Saturn's upper atmosphere that have not been observed or predicted before. They are forced by diurnally varying zonally non‐uniform distributions of Joule heating and ion drag at the high‐latitude auroral regions in both hemispheres and propagate outward from the source region. The supersonic zonal phase speed imposed by Saturn's rotation and the subsonic meridional phase velocity of about 800 m s−1${\\mathrm{s}}^{-1}$form a distinct spiral wave structure. They exhibit features of gravity waves: vertical phase progression opposite to the propagation of wave energy and long vertical wavelengths consistent with the dispersion relation for gravity waves. The amplitudes of the perturbations grow with height, reaching 6%–10% for relative temperature variations and up to 350 m s−1${\\mathrm{s}}^{-1}$for the meridional velocity perturbations. The main effect of these waves is to accelerate the retrograde westerly jets. Plain Language Summary Gravity waves are common in all convectively stable atmospheres. They are caused by a variety of sources and have horizontal extents ranging from a few kilometers to scales comparable to the radius of the planet. In simulations of the Saturnian upper atmosphere, we found a new form of gravity wave that has not been observed or predicted before. The waves are excited at 900–1,000 km above the 1 bar pressure level near the auroral ovals in both hemispheres. They are caused by the changing heating and drag in the auroral regions as Saturn rotates throughout the day. Saturn's large size and fast rotation make the waves move around the planet faster than the speed of sound in Saturn's atmosphere. They spread out from their source, creating a spiral pattern that covers a large part of the planet. We studied these waves and how they affect the global circulation. Unlike gravity waves on Earth and similar planets, which mostly slow down the surrounding winds, these waves in Saturn's upper atmosphere mainly speed up the strong westward jets. Key Points General circulation modeling reveals large‐scale gravity waves in the upper atmosphere of Saturn that have never been reported before Waves are forced by Joule heating and ion drag at high‐latitude auroral regions, propagate outward and form a global spiral structure The net dynamical effect of these zonally supersonic and meridionally subsonic waves is to accelerate the westward retrograde jets

Propagation of internal gravity waves (GWs) from the lower atmosphere into the upper thermosphere, and their dynamical and thermal effects have been studied under low and high solar activity approximated by the F10.7 parameter. It has been done by using a nonlinear spectral parameterization in systematic offline calculations with typical wind and temperature distributions from the HWM and MSISE‐90 models, and with interactive simulations using the University College London Coupled Middle Atmosphere‐Thermosphere‐2 (CMAT2) general circulation model (GCM) under solstice conditions. The estimates have been performed for relatively slow harmonics with horizontal phase velocities less than 100 m s−1, which are not affected by reflection and/or ducting. GW drag and wave‐induced heating/cooling are shown to be smaller below ∼170 km at high solar activity, and larger above. The maxima of GW momentum deposition occur much higher in the upper thermosphere, but their peaks are half as strong, 120 vs 240 m s−1 day−1 in the winter hemisphere when the insolation is large. Instead of strong net cooling in the upper thermosphere, GWs produce a weak heating at high solar activity created by fast harmonics less affected by dissipation. Molecular viscosity increases with solar activity at fixed pressure levels, but seen in Cartesian altitude grids it can either increase or decrease in the lower thermosphere, depending on the height. Therefore, in pressure coordinates, in which most GCMs operate, the influence of larger temperatures can be viewed as a competition between the enhanced dissipation and vertical expansion of the atmosphere.

For the first time, estimates of heating and cooling in the upper thermosphere due to dissipating and breaking gravity waves (GWs) of tropospheric origin have been obtained with a comprehensive general circulation model (GCM). A GW parameterization specifically designed for thermospheric heights has been implemented in the CMAT2 GCM covering altitudes from the tropopause to the F2 region, and simulations for the June solstice have been performed. They reveal that the net thermal effect of GWs above the turbopause is cooling. The largest (up to −170 K d−1 in a zonally and temporally averaged sense) cooling takes place in the high latitudes of both hemispheres near 210 km. The instantaneous values of heating and cooling rates are highly variable, and reach up to 500 and −3000 K d−1 in the F2 region, respectively. Inclusion of the GW thermal effects reduces the simulated model temperatures by up to 200 K over the summer pole and by 100 to 170 K at other latitudes near 210 km.

We examine for the first time the propagation of gravity waves (GWs) of lower atmospheric origin to the thermosphere above the turbopause during a sudden stratospheric warming (SSW). The study is performed with the Coupled Middle Atmosphere‐Thermosphere general circulation model and the implemented spectral GW parameterization of Yiğit et al. (2008). Simulations reveal a strong modulation by SSWs of GW activity, momentum deposition rates, and the circulation feedbacks at heights up to the upper thermosphere (∼270 km). Wave‐induced root mean square wind fluctuations increase by a factor of three during the warming above the turbopause. This occurs mainly due to a reduction of filtering eastward traveling harmonics by the weaker stratospheric jet. Compared to nominal conditions, these GW harmonics propagate to higher altitudes and have a larger impact on the mean flow in the thermosphere, when they are dissipated. The evolution of stratospheric and mesospheric winds during an SSW life‐cycle creates a robust and distinctive response in GW activity and mean fields in the thermosphere above the turbopause up to 300 km. Key Points Gravity wave effects are modeled during a stratospheric warming Gravity wave activity and drag increase dramatically in the thermosphere Gravity wave effects in the thermosphere are extremely variable during an SSW

Results of simulations with a new high-resolution Martian general circulation model (MGCM) (T106 spectral resolution, or ~67-km horizontal grid size) have been analyzed to reveal global distributions of gravity waves (GWs) during the solstice and equinox periods. They show that shorter-scale harmonics progressively dominate with height, and the body force per unit mass (drag) they impose on the larger-scale flow increases. Mean magnitudes of the drag in the middle atmosphere are tens of meters per second per sol, while instantaneously they can reach thousands of meters per second per sol. Inclusion of small-scale GW harmonics results in an attenuation of the wind jets in the middle atmosphere and in the tendency of their reversal. GW energy in the troposphere due to the shortest-scale harmonics is concentrated in the low latitudes for both seasons and is in a good agreement with observations. The vertical fluxes of wave horizontal momentum are directed mainly against the larger-scale wind. Orographically generated GWs contribute significantly to the total energy of small-scale disturbances and to the drag created by the latter. These waves strongly decay with height, and thus the nonorographic GWs of tropospheric origin dominate near the mesopause. The results of this study can be used to better constrain and validate GW parameterizations in MGCMs.

Carbon dioxide (CO2) ice clouds have been routinely observed in the middle atmosphere of Mars. However, there are still uncertainties concerning physical mechanisms that control their altitude, geographical, and seasonal distributions. Using the Max Planck Institute Martian General Circulation Model (MPI-MGCM), incorporating a state-of-the-art whole atmosphere subgrid-scale gravity wave parameterization (Yiğit et al., 2008), we demonstrate that internal gravity waves generated by lower atmospheric weather processes have a wide-reaching impact on the Martian climate. Globally, GWs cool the upper atmosphere of Mars by ∼10 % and facilitate high-altitude CO2 ice cloud formation. CO2 ice cloud seasonal variations in the mesosphere and the mesopause region appreciably coincide with the spatio-temporal variations of GW effects, providing insight into the observed distribution of clouds. Our results suggest that GW propagation and dissipation constitute a necessary physical mechanism for CO2 ice cloud formation in the Martian upper atmosphere during all seasons.

Monitoring excited hydroxyl (OH*) airglow is broadly used for characterizing the state and dynamics of the terrestrial atmosphere. Recently, the existence of excited hydroxyl was confirmed using satellite observations in the Martian atmosphere. The location and timing of its detection on Mars were restricted to a winter season at the north pole. We present three-dimensional global simulations of excited hydroxyl over a Martian year. The predicted spatio-temporal distribution of the OH* can provide guidance for future observations, namely by indicating where and when the airglow is likely to be detected.