Climate Fact: Changes in Cloud Ceilings
Cloud-ceiling height is defined as the base height of the lowest cloud layer when weather conditions are considered overcast. Since the early 1970’s, the average cloud-ceiling height in the lowest 1.24 miles of the atmosphere has been rising at a rate of 86 feet per decade. These cloud ceiling changes were accompanied by a surface temperature increase of 0.6 degrees Fahrenheit per decade from 1975-2003, and a decrease in surface relative humidity. When relative humidity is reduced, cloud bases are forced to develop at higher altitudes and low cloud formation is not as prevalent.
Seasons: Winter, Spring, Summer, Fall
Source: Sun, B., et al. “Changes in cloud-ceiling heights and frequencies over the United States since the early 1950s.” Journal of Climate 20 (2007): 3956-3970 and “Temperature Changes.” Climate Change – Science. U.S. Environmental Protection Agency. Updated 31 March 2008. Accessed 16 November 2008 <http://epa.gov/climatechange/science/recenttc.html>