Mars PCM physics: CO2 cycle

The goal of this page is to summarize key aspects, but theoretical and practical, of the parametrizations in the Mars physics package that enable modeling the Martian CO2 cycle

The key processes

• CO2 condensation: atmospheric condensation. surface condensation
• polar sub-surface ice tables as high thermal inertia "heat reservoirs"
• surface properties (albedo of the surface)

Parametrizations and key parameters in the model

CO2 condensation in the atmosphere

• CO2 ice clouds. These are implemented, but not used in standard simulations.
• CO2 condensation. See routine co2condens.

Polar sub-surface ice tables of high thermal inertia

These are set via the newstart utility. The information itself is stored in the startfi file. For now, the subsurface ice depth and thermal inertia values are set to fit the CO2 cycle thought an inversion of MONS spectrometer data (see Diez et al., 2008) by the routine xvik. One can also use the Planetary Evolution Model to compute the position of the ice table.

Surface properties

In callphys.def one may specify ( by setting flag TESicealbedo to .true. ; recommended) that a climatology based on TES observations be used to drive (nudge) the evolution of CO2 polar caps.

# Impose polar cap surface albedos as observed by TES?
TESicealbedo = .true.
## Coefficient for Northern cap albedoes
TESice_Ncoef=1.6
## Coefficient for Southern cap albedoes
TESice_Scoef=1.6

The sub-options TESice_Ncoef and TESice_Scoef are multiplying factors applied to the TES values, meant to account for non Lambertian effects. In practice this is coded in ...

If a alternative setup with

# Impose polar cap surface albedos as observed by TES?
TESicealbedo = .false.

Then the surface albedo is based on the presence or absence of CO2 ice on the surface. Without CO2 ice the albedo is that of bare ground and if CO2 ice is present it is set to 0.6 (variable albedice in surfdat_h.F90 which stores 2 values one for north and south). In this case, the perennial CO2 ice at the South Pole is represented throught a different albedo set in the callphys.def:

## Albedo of the perenial CO2 ice at the South Pole
albedo_perenialco2 = 0.85