environmental lapse rate

(meteorology) The rate of decrease of temperature with elevation in the atmosphere. Also known as atmospheric lapse rate.

The fall in temperature of stationary air with height, averaging 6 °C per 1000 m. see lapse rate, adiabatic change. This fall in temperature varies greatly with the time of day, and with the nature of the air mass concerned and is, for example, much more rapid in a polar maritime air mass than in a mass of tropical maritime air. This fall of temperature with height in stable air is due to a fall in the density of the air.