Adiabatic Lapse Rate

The troposphere, the lowest layer of Earth's atmosphere, is where most weather occurs. In this layer, temperatures decrease with increasing elevation, explaining why mountaintops are snow-covered. Consequently, objects cool as they rise and warm as they fall in the troposphere.

The rate at which air cools or warms isn't uniform; it depends on the amount of water vapor present. Dry air changes temperature by 9.8 degrees Celsius per 1000 meters in the troposphere. However, moist air cools at a slower rate, typically around 6 degrees Celsius per 1000 meters, though this can vary with moisture content.

When moist air from the ocean is forced upwards by a mountain, it cools at about 6 degrees Celsius per 1000 meters, leading to condensation and cloud formation. After losing its moisture, the air descends the leeward side of the mountain, warming rapidly at 9.8 degrees Celsius per 1000 meters. This phenomenon, known as a foehn wind (or chinook wind), can cause significant and rapid temperature increases, up to 14 degrees Celsius in minutes, but also carries the risk of avalanches due to unstable slopes.