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|lapse rate |
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).
rate of change in temperature observed while moving upward through the Earth's atmosphere. The lapse rate is considered positive when the temperature decreases with elevation, zero when the temperature is constant with elevation, and negative when the temperature increases with elevation (temperature inversion). The lapse rate of nonrising air-commonly referred to as the normal, or environmental, lapse rate-is highly variable, being affected by radiation, convection, and condensation; it averages about 6.5 C per kilometre (18.8 F per mile) in the lower atmosphere (troposphere). It differs from the adiabatic lapse rate, which involves temperature changes due to the rising or sinking of an air parcel. Adiabatic lapse rates are usually differentiated as dry or moist