|lapse rate (lāps) Pronunciation Key
The rate of change of any meteorological phenomenon, especially atmospheric temperature with altitude. The lapse rate varies depending on the ground temperature, time of year (for example, in the Northern hemisphere it is lower in the winter), whether the air is over land or ocean water, and what the degree of moisture is. ◇ The dry adiabatic lapse rate is the lapse rate of a dry mass of air which expands and cools as it rises. This rate is typically -9.8°C (-14.36°F) per 1,000 m (3,280 ft). ◇ The saturated adiabatic lapse rate is the lapse rate of a wet mass of air, which slows down once the dew point has been reached and condensation has started to form. This rate ranges from 4°C (39.2°F) per 1,000 m (3,280 ft) to 9°C (48.2°F) per 1,000 m (3,280 ft).