The environmental lapse rate is found by dividing the change in temperature by the change in altitude. The environmental lapse rate is calculated in terms of a stationary atmosphere and may also be referred to as the temperature gradient.
In general, a lapse rate measures rate at which temperature changes with changes in altitude. The two types of lapse rates are the environmental lapse rate and the adiabatic lapse rate, depending on what air is being measured. An environmental lapse rate measures the change in still air, while the adiabatic lapse rate measures the change as a pocket of air changes altitude as a closed system.