# Dry-adiabatic lapse rate

From AMS Glossary

## dry-adiabatic lapse rate

- A 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*/*c*_{pd}, where*g*is gravitational acceleration and*c*_{pd}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.

- The adiabatic lapse rate of unsaturated air containing water vapor.

This differs from definition 1 by the factorwhere*r*_{v}is the mixing ratio of water vapor and*c*_{pv}is the specific heat of water vapor.