Atmospheric condensate rainout

Condensation followed by gravitational settling removes chemical elements from an atmospheric layer. The remaining gas may be in local chemical equilibrium with a depleted elemental inventory, while the column is not a closed equilibrium system.

A sufficiently cold layer condenses a volatile or refractory carrier and limits its transport to higher layers. Water depletion above the terrestrial tropopause and titanium-bearing condensates in some hot Jupiter models illustrate this process.