# Difference between revisions of "Adiabatic lapse rate"

From Glossary of Meteorology

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− | <div class="definition"><div class="short_definition"> | + | <div class="definition"><div class="short_definition">The rate of decrease in [[temperature]] with height via an [[adiabatic process]].</div><br/> </div> |

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+ | #<div class="definition"><div class="short_definition">Dry-adiabatic lapse rate</div> <div class="paragraph">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]].</div> <div class="paragraph">This lapse rate is ''g''/''c''<sub>''pd''</sub>, where ''g'' is the gravitational [[acceleration]] and ''c''<sub>''pd''</sub> is the [[specific heat]] of dry air at constant [[pressure]], approximately 9.8°C km<sup>−1</sup>. [[Potential temperature]] is constant with height in an [[atmospheric layer]] with this lapse rate.</div><br/> | ||

+ | #<div class="definition"><div class="short_definition">Moist-unsaturated adiabatic lapse rate</div> <div class="paragraph">The adiabatic lapse rate of unsaturated air containing [[water vapor]].</div> <div class="paragraph">This differs from definition 1 by the factor <div class="display-formula"><blockquote>[[File:ams2001glos-De50.gif|link=|center|ams2001glos-De50]]</blockquote></div> where ''r''<sub>''υ''</sub> is the [[mixing ratio]] of water vapor and ''c''<sub>''pυ''</sub> is the specific heat of water vapor.</div><br/> | ||

+ | #<div class="definition"><div class="short_definition">Moist-adiabatic lapse rate (or saturation-adiabatic lapse rate or moist-saturated adiabatic lapse rate)</div> <div class="paragraph">The rate of decrease of temperature with height along a [[moist adiabat]].</div> <div class="paragraph">It is given approximately by Γ<sub>''m''</sub> in the following: <div class="display-formula"><blockquote>[[File:ams2001glos-Me16.gif|link=|center|ams2001glos-Me16]]</blockquote></div> where ''g'' is the gravitational acceleration, ''c''<sub>''pd''</sub> is the specific heat at constant pressure of dry air, ''r''<sub>''υ''</sub> is the mixing ratio of water vapor, ''L''<sub>''υ''</sub> 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 process|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 ''L''<sub>''υ''</sub> replaced by the latent heat of [[sublimation]].</div><br/> | ||

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+ | <p>''Term edited 17 June 2021.''</p> | ||

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## Revision as of 12:31, 17 June 2021

## adiabatic lapse rate

The rate of decrease in temperature with height via an adiabatic process.

- 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*/*c*_{pd}, where*g*is the 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. - Moist-unsaturated adiabatic lapse rateThe adiabatic lapse rate of unsaturated air containing water vapor.This differs from definition 1 by the factorwhere
*r*_{υ}is the mixing ratio of water vapor and*c*_{pυ}is the specific heat of water vapor. - 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 Γ
_{m}in the following:where*g*is the gravitational acceleration,*c*_{pd}is the specific heat at constant pressure of dry air,*r*_{υ}is the mixing ratio of water vapor,*L*_{υ}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*L*_{υ}replaced by the latent heat of sublimation.

*Term edited 17 June 2021.*