What is the Lapse Rate?

By Joel Gratz
7/11/2013 10:30:40 AM

We all know that the temperature at the top of a mountain is colder than at the base (usually this is the case... there are, of course, exceptions). But many ski areas don't have weather stations at both the base and the summit, so it's hard to know what to expect up top when you're at the bottom about ready to start your day. Thankfully there is a shortcut.

If it is snowing or you're in a cloud, the air temperature will decrease about 3.3 degrees Fahrenheit for every 1,000 feet gained in elevation. If the air is not saturated and conditions are dry, the temperature will decrease at 5.5 degrees Fahrenheit for every 1,000 feet gained in elevation. Credit: OnTheSnow

This shortcut is called the Lapse Rate and it describes how the temperature changes with altitude. While the lapse rate is a constant, in the real world the actual temperature can change based on aspects beyond just the physics of the atmosphere, such as the direction the slope is facing, the make-up of the slope (rocks, snow, a lodge) and other factors.

Still, here's the way to approximate the temperature at different elevations. When the air is dry, the temperature decreases about 5.5 Degrees Fahrenheit for every 1,000 feet gained in elevation. For example, if the base of the mountain is about 3,000 feet lower than the summit and the temperature at the base is 20 Degrees, you could estimate the summit temperature at about 5 Degrees. In practice, the summit temperature can be a bit warmer than this approximation because the ground can stay a bit warmer than freely-moving air just above and around the summit.

Continue Reading on OnTheSnow.com >