Temperature Lapse Rate Calculator
Dry Adiabatic (DALR)
Moist/Saturated (SALR)
Standard Atmosphere (ISA)
Custom Rate
Enter a positive number for cooling with height.
Calculation Results
Altitude Change:
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Lapse Rate Used:
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Temperature Change:
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Final Temperature:
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Understanding Temperature Lapse Rate
The Temperature Lapse Rate is a meteorological parameter that describes the rate at which atmospheric temperature decreases with an increase in altitude. Whether you are a pilot, a mountaineer, or a meteorology student, understanding how temperature changes as you ascend is critical for safety and planning.
Key Types of Lapse Rates
In atmospheric thermodynamics, there are three primary lapse rates used for calculations:
- Dry Adiabatic Lapse Rate (DALR): This rate applies to unsaturated air parcels (air with less than 100% relative humidity). The standard value is approximately 9.8°C per 1,000 meters (or 5.4°F per 1,000 feet). Because dry air does not release latent heat through condensation, it cools rapidly as it rises and expands.
- Moist (Saturated) Adiabatic Lapse Rate (SALR/MALR): Once air reaches saturation (dew point), water vapor condenses into clouds, releasing latent heat. This heat offsets some of the cooling caused by expansion. Consequently, the moist lapse rate is lower, typically averaging around 6.0°C per 1,000 meters (3.3°F per 1,000 feet), though it varies with temperature.
- Environmental Lapse Rate (ELR): This is the actual observed decrease in temperature at a specific time and location, which can vary based on weather conditions. The International Standard Atmosphere (ISA) assumes a standard average lapse rate of 6.5°C per 1,000 meters (3.5°F per 1,000 feet).
How to Calculate Temperature at Altitude
To estimate the temperature at a specific altitude, you can use the following formula:
Tfinal = Tinitial – ( Lapse Rate × ( Altitudefinal – Altitudeinitial ) / 1000 )
Where:
- Tfinal is the temperature at the target altitude.
- Tinitial is the starting temperature (e.g., at sea level or ground station).
- Altitude Difference is divided by 1,000 because lapse rates are typically expressed per 1,000 units (meters or feet).
Applications of Lapse Rate
Aviation: Pilots use lapse rates to determine the freezing level, which is crucial for avoiding structural icing on aircraft.
Hiking and Mountaineering: Hikers use this calculation to prepare for colder temperatures at summits. For example, if it is 20°C at the trailhead, the summit 2,000 meters higher could be near freezing depending on the lapse rate.
Weather Forecasting: The stability of the atmosphere is determined by comparing the Environmental Lapse Rate to the Dry and Moist Adiabatic rates. This comparison helps predict thunderstorm development and turbulence.