Thermodynamic simulation of the seasonal cycle of temperature, pressure and ice caps on Mars

We present a thermodynamic model to simulate the Mars atmospheric temperature and pressure, the regolith temperature and the polar CO 2 ice caps vertical thickness and horizontal extent. This is done using the temperatures of the atmosphere and regolith for each Martian day of the year, determined from the thermodynamic equation. Assuming a CO 2 atmosphere, we calculate its emission spectrum using the spectral calculator E-Trans with the HITRAN database (E-Trans/HITRAN), resulting in the band of 15  microns  and the rest transparent, through which the radiation emitted by the regolith and ice caps (considered as black bodies) goes toward space; we also include the atmospheric dust solar radiation extinction and its longwave emission. The equation calculates the energy balance between the absorbed solar radiation and the outgoing longwave radiation, incorporating also the latent heat released by CO 2 condensation, the sensible heat flux from the surface to the atmosphere, the latent heat flux due to the CO 2 ice sublimation and the heat exchange between the surface regolith layer and its lower layers, and the atmospheric planetary scale horizontal turbulent heat transport with an exchange coefficient, which is an order of magnitude smaller than that employed in the terrestrial troposphere. Considering a long-time average, the regolith vertical temperature profile is explicitly found using the thermal inertia including conductivity; its temperature regulation is achieved through the thermal conduction from the surface during the warm season this stored energy goes back to the surface during the cold season. Our model simulates the seasonal variation of the polar ice caps and consequently of the surface atmospheric pressure, through the CO 2 mass balance between them. Finally it is explicitly shown that the amplitude of the global seasonal pressure cycle is modulated by a local thermal-orographic effect, which increases (decreases) this amplitude in the low (high) regions, and agrees with the observations of the Viking Landers 1 and 2, and the Mars Climate Data Base; our prediction for Hellas Planitia, gives an amplification factor of up to 2.15, coinciding with other authors.