Saturation equivalent potential temperature

From Glossary of Meteorology

saturation equivalent potential temperature

Saturation equivalent potential temperature (represented as θes) is a special case of equivalent potential temperaturee) computed by assuming an air parcel is saturated (i.e., r = rsat in the equation for θe)and thus represents the theoretical maximum θe. Both θes and θe are themselves special cases of potential temperature (θ), accounting for the latent heat release due to condensation of water vapor by lifting the parcel to a new temperature and pressure via a pseudoadiabatic process prior to computing the potential temperature. Hence, θes is conserved for a reversible moist adiabatic process. The relationship between the three types of potential temperature can be described as follows, where r represents the parcel water vapor mixing ratio and rsat is the saturation value of water vapor mixing ratio based on the parcel temperature and pressure:

r = rsat (saturated environment): θe = θes,

r = 0 (dry environment): θe = θ, and

0 < r < rsat (unsaturated moist parcel): θ < θe < θes.

Bohren, C. F., and B. A. Albrecht, 1998: Atmospheric Thermodynamics. Oxford University Press, 293–294.

(term edited 8/22/2014)

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