CO2 Condensation (Generic PCM)

This page describes the condense_co2 routine of the Generic PCM. This routine, inherited from the Mars PCM, only works for atmosphere where CO2 is the background, dominant gas. If CO2 is a trace, variable gas, you should use the generic condensation scheme.

Nucleation and Condensation of CO2

The condensation and nucleation temperature are calculated using Fanale's formula (subroutines get_tcond_co2 and get_tnuc_co2): \begin{equation} T_{\rm cond}= \begin{cases} \frac{-3167.8}{\log(0.01\times P)-23.23} & {\rm if }P<P_{\rm triple}=518000~{\rm Pa}\\ 684.2-92.3\times\log(P)+4.32\times\log(P)^2 & {\rm otherwise} \end{cases} \end{equation} At the moment, we consider $$T_{\rm nuc}=T_{\rm cond}$$.

In the atmosphere

The routine iterates condensation and sedimentation in the atmosphere column over 20 subtimesteps. It computes:

Sedimentation of CO2 aerosols

Using the subroutines co2_reffrad for the aerosols particles radius, the Stokes velocity is calculated with subroutine stokes and the tracers are updated using subroutine vlz_fi.

Condensation and sublimation of CO2 in the atmosphere

If the local temperature is below the nucleation temperature or CO2 ice is present, condensation / sublimation tendencies for CO2 tracers (ice and gas) as well as temperature (via latent heat effect) are calculated.

On the ground

Condensation and sublimation on the ground

Surface tracer and temperature tendencies due to condensation or sublimation at the surface as well as CO2 ice accumulation on the ground due to icefall are then calculated. Importantly, surface pressure is adjusted to account for variations in CO2 ice cover.

Albedo and emissivity

Finally, albedo and emissivity are re-calculated as a function of the amount of CO2 ice deposited.