When scientists talk about the cryosphere, they mean the places on Earth where water is in its solid form, frozen into ice or snow. Read more ...
Cryosphere Glossary
saturation
the condition in which the partial pressure of any fluid constituent (water in the atmospheric air) is equal to its maximum possible partial pressure under the existing environmental conditions, such that any increase in the amount of that constituent will initiate within it a change to a more condensed state; evaporation ceases under such conditions.