Clouds serve as reflectors of incoming solar radiation, also called insolation, which is the short-wave radiated energy from the sun that propagates through the Earth's atmosphere. However, the extent to which an individual cloud reflects insolation depends on its thickness, as thin clouds reflect less insolation than thick clouds.
High clouds, including cirrus, cirrostratus and cirrocumulus, are found above 20,000 feet. These clouds are primarily composed of suspended ice particles and tend to be very thin. This thinness allows most of the insolation to pass through cirrus-type clouds without losing much energy due to reflection.
Middle clouds, including altocumulus and altrostratus, are found between 6,500 and 23,000 feet. Altocumulus clouds consist of water droplets, while altostratus clouds consist of ice and water droplets. Altocumulus clouds tend to be thicker than altostratus clouds, and both types of clouds tend to be thicker than cirrus-type clouds. As such, the middle clouds tend to reflect a higher proportion of insolation than high clouds.
Low clouds, including stratus, nimbostratus and cumulus, are found below 6,000 feet. These clouds are entirely composed of water droplets. Their thickness causes them to reflect a high proportion of insolation that reaches this low altitude.
Cumulonimbus clouds, also called storm clouds, tend to reflect the highest proportion of insolation. Their altitude ranges from near the surface of the Earth to over 50,000 feet.