Mean and gravity wave structures and variability in the Mars upper atmosphere inferred from Mars Global Surveyor and Mars Odyssey aerobraking densities

Abstract

[1] We have used density measurements obtained during aerobraking (AB) on Mars Global Surveyor and Mars Odyssey to examine mean densities and the characteristics and variability of gravity waves (GWs) in the upper atmosphere of Mars. Mean densities exhibit variability with latitude and season and in response to variable forcing and filtering from below. These data also reveal significant variability of GWs, both spatially and temporally. In general, GW amplitudes increase, while apparent horizontal scales remain the same, with increasing altitude. The dominant spatial scales at the lower AB altitudes are typically $20-200 km and density fluctuations vary from $5 to 50%, though even larger values are occasionally observed. GW amplitudes also vary significantly with season, being generally larger in winter and at middle and high latitudes, and apparently reflecting mean source and filtering conditions. Amplitudes also appear to vary with longitude and time and may provide clues to variability of, and interactions with, largerscale motions.

Extending MGS-TES temperature retrievals in the martian atmosphere up to 90km: Retrieval approach and results

“…The RMS values of temperature variability listed in the third column of Table 3 were obtained from the analysis of the entire database subtracting the effects of the noise-induced variability. Large observed temperature variability is expected at these heights, and the increase of its RMS value with increasing altitude can be explained by the growth of GW amplitudes in the martian atmosphere (Fritts et al, 2006). The absolute values of our retrieved RMS temperature variability are comparable with the RMS of GW amplitude inferred from MCS observations and wind RMS (see Section 4.2).…”

Scale-dependent infrared radiative damping rates on Mars and their role in the deposition of gravity-wave momentum flux

“…Taken at face value, this would imply much weaker orographic forcing of gravity-wave momentum flux on Mars relative to Earth. Yet surface flow patterns, and particularly orographic relief, would (if anything) seem to suggest the opposite, and the limited direct measurements of high-altitude gravity waves on Mars to date seem to support this countervailing viewpoint (e.g., Fritts et al, 2006).…”

“…Thus vertical structure in atmospheric temperature profiles can significantly change IR cooling rates. At higher altitudes where cooling rates on Mars are the largest, most of the short vertical scale structure in atmospheric temperature profiles is produced by gravity wave oscillations (Fritts et al, 2006;Creasey et al, 2006), which the GCMs do not resolve. This suggests a potentially important interaction between gravity wave dynamics and IR radiative cooling that the existing uncoupled parameterizations of each process in Mars GCMs miss entirely.…”

Application of MAVEN Accelerometer and Attitude Control Data to Mars Atmospheric Characterization

“…Such measurements at Mars have identified a rapid thermospheric response to a regional dust storm (Keating et al 1998), a high-altitude polar warming (Keating et al 2003;Bougher et al 2006), gravity waves (Fritts et al 2006), and tides (Forbes et al 2002). They have also provided significant tests of Mars atmospheric circulation models and pointed to specific needs in the model physical parameterizations (see Bougher et al 2006, 2008, andreferences therein).…”

“…Such a wave might be a vertically propagating gravity wave, as it is predicted to have maximum amplitudes near the winter polar jet, i.e. 50 • -70 • latitudes (Fritts et al 2006).…”