Friday 27 June 2014
In meteorology, a cloud is a visible mass of liquid droplets or frozen crystals made of water or various chemicals suspended in the atmosphere above the surface of a planetary body. These suspended particles are also known as aerosols and are studied in the cloud physics branch of meteorology. Terrestrial cloud formation is the result of air in Earth's atmosphere becoming saturated due to either or both of two processes; cooling of the air and adding water vapor. With sufficient saturation, precipitation will fall to the surface; an exception is virga, which evaporates before reaching the surface. Clouds in the troposphere, the atmospheric layer closest to Earth's surface, have Latin names due to the universal adaptation of Luke Howard's nomenclature. It was introduced in December 1802 and became the basis of a modern international system that classifies these tropospheric aerosols into several physical forms or categories, then cross-classifies them into families of low-, middle- and high-etage according to cloud-base altitude range above Earth's surface. Clouds with significant vertical extent occupying more than one étage are often considered a separate family. One physical form shows free-convective upward growth into low or vertical heaps of cumulus. Source
