What are Cirrus Clouds?
The most common form of high-level clouds are thin and often wispy cirrus clouds. Typically found at heights greater than 20,000 feet (6,000 meters), cirrus clouds are composed of ice crystals that originate from the freezing of supercooled water droplets. Cirrus clouds generally occur in fair weather and point in the direction of air movement at their elevation. The formation of cirrus clouds has both a heating and cooling effect on the earth's surface. Cirrus clouds cool the surface of earth by reflecting solar radiation into space (albedo effect). Additionally, cirrus clouds have the ability heat the earth by trapping infrared radiation from the surface of the earth (greenhouse effect).