When trying to calculate the adiabatic lapse rate of moist air based on known values of basic thermodynamic properties of the constituents (ice, water, vapor,...) I came to the following question:

Lapse rate of moist air is less as compared to dry air because of the latent head released during condensation of water-vapor.

Now, below 0°C there is no liquid phase in equilibrium, therefore instead of the latent heat of evaporation $L_{ev}$ of liquid I used the value for sublimation $L_{sub}$. However, of course $L_{sub} > L_{ev}$, so according to my calculations the lapse rate must have a discontinuity at 0°C (see graph, where the dotted line is the dry lapse rate).

This discontinuity is not in accordance with observation - so where is my fault? What happens in rising air that this effect is not visible? enter image description here

  • 5
    $\begingroup$ The fallacy is: Water becomes ice below 0°C. In the atmosphere water will often be "supercooled". It might be worth checking the "Bergeron-Findeisen process". A nice resource is: Physics and Dynamics of Clouds and Precipitation by Pao K. Wang. $\endgroup$ Apr 28, 2023 at 21:41
  • 3
    $\begingroup$ @JoschaFregin Classic home experiment - take a bottle of distilled water and keep it in the fridge. It never freezes even below 0 degrees. The same is observed in the clouds $\endgroup$
    – user1066
    Apr 29, 2023 at 14:12


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