Question: As a skier in Virginia and West Virginia, we are frequently impacted by inversions at the mountain-top height. What do pilots need to know about temperature inversions? I have yet to find a good discussion of them.
Answer: Before we can discuss temperature inversions, we need to explore the more generic concept of atmospheric lapse rates. A lapse rate is simply the change in temperature over a given change in altitude.
Pilots are taught during their primary training that the standard lapse rate is 2 degrees Celsius for every 1,000-foot gain in altitude. That means, on an average day, the atmosphere “cools” at this rate. In other words, the higher you ascend in the troposphere, the colder it gets. We refer to this as a “positive” lapse rate.
