Table of Contents
Temperature Lapse Rate
The temperature lapse rate is the rate at which air temperature decreases with increasing altitude in the troposphere. The standard lapse rate is 6.5°C per 1,000 meters (about 3.56°F per 1,000 feet). This occurs because air expands as pressure decreases with altitude, and expanding gas cools due to the laws of thermodynamics.
This relationship is fundamental to meteorology, aviation, mountaineering, and climate science. Pilots use lapse rates to calculate density altitude, which affects aircraft performance. Mountaineers use it to prepare for cold conditions at summit altitudes.
Standard Atmosphere Model
Where T(h) is temperature at altitude h, T0 is sea level temperature, and L is the lapse rate (6.5°C/km in the standard atmosphere). This linear model applies up to the tropopause at approximately 11 km, above which temperature remains roughly constant.
Standard Atmosphere Temperature
| Altitude (m) | Temperature (°C) | Temperature (°F) |
|---|---|---|
| 0 | 15.0 | 59.0 |
| 1,000 | 8.5 | 47.3 |
| 3,000 | -4.5 | 23.9 |
| 5,500 | -20.8 | -5.4 |
| 8,849 | -42.5 | -44.5 |
| 11,000 | -56.5 | -69.7 |
FAQ
Is the lapse rate always 6.5C/km?
No. The standard value is an average. Actual lapse rates vary with weather conditions, moisture content, and geography. The dry adiabatic lapse rate is 9.8C/km, while the moist adiabatic rate ranges from 4 to 9C/km depending on moisture. Temperature inversions can even cause temperature to increase with altitude.
What happens above the tropopause?
Above the tropopause (about 11 km), the stratosphere begins where temperature remains constant or increases slightly with altitude due to ozone absorption of UV radiation. This layer extends to about 50 km. Above that, temperature behavior changes again in the mesosphere and thermosphere.
How cold is Mount Everest summit?
Using the standard lapse rate from a 15C sea level, the summit of Everest at 8,849 m would be about -42.5C. Actual temperatures range from -20C in summer to -60C in winter, depending on weather conditions and wind chill, which can make it feel even colder.