The term "saturation value" refers to the maximum limit or level that something can reach. It is the point at which no further increase or change is possible. Full definition
It may be that Lindzen was just giving an estimate off the top of his head in a hearing, but the question is nonetheless interesting to explore further because it provides perspective on how to decompose the greenhouse effect into its individual components and the underlying implications of having a mixture of both condensing (i.e., those that reach saturation values and precipitate from the air) and non-condensing greenhouse gases. (skepticalscience.com)
If it reverses, we can treat the value at the point of reversal (marking a maximum height or depth of the hill or valley in the net upward flux spectrum) as the saturation value, and then include some additional effect at the center of the band for additional increases in CO2 that have the opposite sign as the band widenning in their contributions to radiative forcing. (realclimate.org)
is the latent heat flux; -LRB--RRB-, are the surface wind speed (zonal and meridional components) and air specific humidity at 10 m height and neutral stratification; and is the specific humidity at the sea surface equivalent to the saturation value at the sea surface temperature; l is the coefficient for latent heat of evaporation;? (cersat.ifremer.fr)