GW also generate significant density fluctuations in the upper atmosphere experienced by spacecraft aerobraking or making in situ observations of Mars’s upper atmosphere ( Tolson et al., 2005 Creasey et al., 2006b Fritts et al., 2006).

Local temperature fluctuations created by GW also may enable CO 2 ice clouds to form high in Mars’s middle atmosphere, where mean temperatures are too warm for CO 2 to condense ( Spiga et al., 2012 Yiğit et al., 2015, 2018).

The observation of middle atmospheric polar warming (at the winter solstitial and equinoctial poles) ( Conrath et al., 2000 McCleese et al., 2008 McCleese et al., 2010) and its higher magnitude during dust storms ( Wilson, 1997 Smith, 2004) has raised further interest in Martian GW and in alternative mechanisms for generating polar warming, such as radiative forcing by tropical water ice clouds ( Wilson et al., 2008). GW drag, along with analogous planetary wave and tidal drag, may be especially potent during global dust storm activity ( Kuroda et al., 2009). GW also are important for the atmospheric dynamics of Mars, where GW drag is thought to close the westerly winter jets and drive a downwelling circulation that heats the winter polar middle atmosphere significantly above radiative equilibrium (e.g., Jaquin, 1989 Barnes, 1990 Medvedev et al., 2011b, a Kuroda et al., 2015, 2016). GW also stimulate the formation of polar stratospheric clouds (e.g., Fritts et al., 1993 Chandran et al., 2009 Hoffmann et al., 2017). Along with planetary waves, GW help maintain a seasonally reversing circulation in the mesosphere, excite the quasi-biennial oscillation, and control the stability of the polar stratospheric vortices (e.g., Holton, 1982 Dunkerton, 1997 Albers and Birner, 2014). Gravity waves (GW) enable the circulation near Earth’s surface to affect the middle and upper atmospheric circulation by transporting heat and momentum through strongly stratified atmospheric layers ( Holton et al., 1995 Yamanaka, 1995 Fritts and Alexander, 2003 Yiğit and Medvedev, 2015). The spatial distribution of wave activity is consistent with topographic sources being dominant, but contributions from boundary layer convection and other convective processes are possible. We find that: (1) strong, moderately intermittent gravity wave activity is scattered over the tropical volcanoes and throughout the middle to high latitudes of both hemispheres during fall and winter, (2) gravity wave activity noticeably departs from climatology during regional and global dust storms and (3) strong, intermittent variance is observed at night in parts of the southern tropics during its fall/winter, but frequent CO 2 ice clouds prevents unambiguous attribution to GW activity. These observations are sensitive to gravity waves at 20-30 km altitude with wavelength properties (λ h=10-100 km, λ z > 5 km) that make them likely to affect the dynamics of the middle and upper atmosphere.

Here is presented an analysis of variance in calibrated radiance at 15.4 μm (635-665 cm −1) from off-nadir and nadir observations by the Mars Climate Sounder (MCS) on board Mars Reconnaissance Orbiter (MRO) a major expansion in the observational data available for validating models of Martian gravity wave activity. At Earth, the statistical variance in satellite observations of thermal emission above the instrumental noise floor has been used to enable measurement of gravity wave activity at a global scale. Gravity waves in Mars’s atmosphere strongly affect the general circulation as well as middle atmospheric cloud formation, but the climatology and sources of gravity waves in the lower atmosphere remain poorly understood.

Gravity on mars