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.

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

(term edited 8/22/2014)


Copyright 2022 American Meteorological Society (AMS). For permission to reuse any portion of this work, please contact permissions@ametsoc.org. Any use of material in this work that is determined to be “fair use” under Section 107 of the U.S. Copyright Act (17 U.S. Code § 107) or that satisfies the conditions specified in Section 108 of the U.S.Copyright Act (17 USC § 108) does not require AMS’s permission. Republication, systematic reproduction, posting in electronic form, such as on a website or in a searchable database, or other uses of this material, except as exempted by the above statement, require written permission or a license from AMS. Additional details are provided in the AMS Copyright Policy statement.