<P> Lapse rate is the rate at which Earth's atmospheric temperature decreases with an increase in altitude, or increases with the decrease in altitude . Lapse rate arises from the word lapse, in the sense of a gradual change . </P> <P> Although this concept is most often applied to Earth's troposphere, lapse rate can be extended to any gravitationally supported parcel of gas . </P>

The term for the rate at which the actual air temperature changes with altitude in the atmosphere is