environmental lapse rate (ELR) The rate at which the air temperature changes with height in the atmosphere surrounding a cloud or a rising parcel of air. The overall average rate is a decrease of about 6.5°C/km, but the rate varies greatly in different regions of the world, in different airstreams, and at different seasons of the year. Where the lapse rate of temperature is negative (temperature increases with height), an inversion is said to exist.

environmental lapse rate (ELR) The rate at which the air temperature changes with height in the atmosphere surrounding a cloud or a rising parcel of air. The overall average rate is a decrease of about 6.5°C/km, but the rate varies greatly in different regions of the world, in different airstreams, and at different seasons of the year. Where the lapse rate of temperature is negative (temperature increases with height), an inversion is said to exist.