The process of air saturation and supersaturation

The process of air saturation and supersaturation: PV=nRT, and saturation means that the partial pressure P of water vapor in the air reaches its saturated vapor pressure.

The saturated vapor pressure of water is proportional to the temperature. The higher the temperature, the higher the saturated vapor pressure, and the stronger the ability of air to hold water, the less likely it is to be saturated. The saturated vapor pressure of water vapor can be found in the table. At present, as far as weather observation is concerned, WMO recommends using Goff-Gratch formula to calculate saturated vapor pressure. Note, however, that the use temperature of this formula is limited.

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Meteorology, supersaturation means that in a certain space, the water vapor content exceeds the saturation value relative to pure water or pure ice, that is, the relative humidity is greater than 100%. In the laboratory, pure wet air without impurities can be cooled to 300% supersaturation without condensation.

Because water vapor condensation needs to condense nuclei, pure water needs to form embryos of liquid water, and it needs to reach a certain degree of supersaturation to overcome the free energy on the surface of embryos of water droplets. In fact, there are abundant condensation nuclei in the atmosphere, and only a small supersaturation is needed to form water droplet embryos.

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