Saturation ratio
= Saturation ratio
{title2=$S=p_v/p_{\rm sat}$}
The ambient <water> <vapor> <partial pressure> divided by the equilibrium <saturation pressure> over a stated reference surface at the same <temperature>. Relative to flat pure <water>, <atmospheric supersaturation> is $s=S-1$. A curved solute-containing <cloud droplet> generally has a different equilibrium <saturation ratio> from unity.