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Precipitation occurs when moist air rises to cooler altitudes, condensing the water out of the air into droplets. Once these droplets become heavy enough, often by coalescing around motes of dust or other particles, they... More »

www.reference.com Science Weather & Tides Clouds

Rain clouds turn gray or black because thick clouds saturated with rain drops scatter sunlight coming through the clouds. When less direct sunlight gets to the bottom of clouds, they appear darker to the human eye. Thin ... More »

www.reference.com Science Weather & Tides Clouds

Dark rain clouds are called stratus clouds. They are rainy, dense, dark or snowy clouds that sometimes appear as white cottony clumps surrounded by blue sky. More »

www.reference.com Science Weather & Tides Clouds
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Cumulonimbus clouds form when warm, moisture-laden air travels upward and is cooled, condensing into a tall body of water droplets. Cumulonimbus clouds can reach up to 10 kilometers in height and take on a flat-topped ap... More »

www.reference.com Science Weather & Tides Clouds

Cirrocumulus clouds are composed of supercooled water droplets and form through shallow convection within thin labile layers of air. These high-altitude clouds form between 16,600 and 30,000 feet. More »

www.reference.com Science Weather & Tides Clouds

Stratus clouds are formed when an upward-moving current of air collides with a thinner layer of air above it, causing water drops to form. The name "stratus cloud" derives from the shape of the cloud formation, where the... More »

www.reference.com Science Weather & Tides Clouds

Cirrus clouds are made up of ice crystals that form when supercooled water droplets freeze. These wispy and thin clouds are usually at elevations higher than 20,000 feet and are created from other clouds that go through ... More »

www.reference.com Science Weather & Tides Clouds