Adiabatic lapse rate
An adiabatic lapse rate is the rate at which the temperature of a fluid changes when it is subjected to changes in pressure. (See Adiabatic lapse for a more thorough treatment of this subject). Adiabatic lapse rate is used as an analytic device usually with reference to Earth's atmosphere.
Adiabatic lapse rate is measured in units of temperature divided by altitude – a common unit is °C per 1000 feet.
Adiabatic lapse rate varies with the air's moisture content. Dry adiabatic lapse rate (DALR) occurs when the humidity is low, and is a constant 2.98 °C/1000ft (9.78 °C/km). When the air is saturated with water vapor, the moist adiabatic lapse rate (MALR) applies. It varies with temperature and pressure, but is usually near 1.5 °C/1000ft (4.9 °C/km).
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