Wave–photochemistry coupling and its effect on water vapor, ozone and airglow variations in the atmosphere of Mars

A one-dimensional photochemical–transport model for the martian lower atmosphere has been developed to study the diurnal cycles of wave–photochemistry coupling. The model self-consistently calculates water vapor mixing ratio profiles, which exhibit strong vertical and diurnal variations mainly due to the high sensitivity of the saturation vapor pressure to temperature variation. The dynamical coupling of water vapor caused by the temperature variation induced by tidal waves, vertical transport parameterized by eddy diffusion, and linear relaxation introduced in condensation–sublimation processes all have similar timescales of diurnal variation. This leads to a significant asymmetric distribution of water vapor concentration as a function of local time. As a result, the net effect of the temperature variation by tidal waves depletes the water vapor concentration in its diurnal mean. The coupling processes also deplete the diurnally averaged HOx concentration, which in turn leads to significant enhancements of both ozone concentration and the associated airglow emissions in the martian atmosphere. The model also shows explicitly the importance of photochemical–transport coupling to the airglow emissions and its implications in species retrievals when the photochemical times of the excited states are comparable to the timescale of diurnal variation.