Weather Words: Adiabatic Cooling

Have you ever been hiking and noticed that the air gets cooler as you ascend? Or mountain bike down a mountain and realize the temperature is much warmer at the bottom? This is adiabatic cooling. The air naturally cools as we get higher in elevation because the air gets less dense, allowing the air to expand. This expansion requires energy, which in turn drops the temperature.

If the air is dry, the temperature cools at a rate of 5.5 degrees Fahrenheit every 1,000 feet. If the air is saturated, the temperature won’t drop as quickly. This is called the dry/moist adiabatic lapse rate. If the temperature drops enough to reach the dew point, then you will find yourself hiking in clouds.

Since our example is about the mountains, one of the most common forms of adiabatic cooling is called orographic lifting. This is when air is forced up the windward side of the mountain, cooling as it ascends (adiabatic cooling). The opposite is true for the leeward side of the mountain. Air descends down the mountain, warming on the way down.

Jennifer Gray is a weather and climate writer for weather.com. She has been covering some of the world's biggest weather and climate stories for the last two decades.