What is the wet adiabatic lapse rate?

The wet adiabatic lapse rate refers to the rate at which temperature decreases with altitude when moisture is present in the air and condensation occurs. This lapse rate is generally around 1.5º Celsius for every 1,000 feet of elevation.

When air rises, it expands due to lower atmospheric pressure at higher altitudes, which typically causes the air to cool at the dry adiabatic lapse rate of about 3º Celsius per 1,000 feet. However, when the air contains moisture, as it rises and cools, the moisture can condense into clouds and release latent heat. This release of heat counteracts some of the cooling effect, resulting in a slower temperature decrease compared to the dry adiabatic rate.

The correct rate of approximately 1.5º Celsius per 1,000 feet allows for the effect of this heat release during the phase change of water. This understanding is critical for understanding stability and potential weather developments in the atmosphere, particularly in areas of rising air.