Adiabatic lapse rate
From Glossary of Meteorology
adiabatic lapse rate
- Dry-adiabatic lapse rateA process lapse rate of temperature, the rate of decrease of temperature with height of a parcel of dry air lifted by a reversible adiabatic process through an atmosphere in hydrostatic equilibrium.This lapse rate is g/cpd, where g is the gravitational acceleration and cpd is the specific heat of dry air at constant pressure, approximately 9.8°C km−1. Potential temperature is constant with height in an atmospheric layer with this lapse rate.
- Moist-adiabatic lapse rate (or saturation-adiabatic lapse rate or moist-saturated adiabatic lapse rate)The rate of decrease of temperature with height along a moist adiabat.It is given approximately by Γm in the following:where g is the gravitational acceleration, cpd is the specific heat at constant pressure of dry air, rυ is the mixing ratio of water vapor, Lυ is the latent heat of vaporization, R is the gas constant for dry air, ε is the ratio of the gas constants for dry air and water vapor, and T is temperature. This expression is an approximation for both the reversible moist-adiabatic lapse rate and the pseudoadiabatic lapse rate, with more accurate expressions given under those definitions. When most of the condensed water is frozen, this may be replaced by a similar expression but with Lυ replaced by the latent heat of sublimation.
Term edited 17 June 2021.