Cirrus is a genus of high cloud made of ice crystals. Cirrus clouds typically appear delicate and wispy with white strands. Cirrus are usually formed when warm, dry air rises, causing water vapor deposition onto rocky or metallic dust particles at high altitudes. Globally, they form anywhere between 4,000 and 20,000 meters above sea level, with the higher elevations usually in the tropics and the lower elevations in more polar regions.
Sky containing different types of cirrus clouds
Cirrus castellanus
Cirrus fibratus
Cirrus floccus
In meteorology, a cloud is an aerosol consisting of a visible mass of miniature liquid droplets, frozen crystals, or other particles suspended in the atmosphere of a planetary body or similar space. Water or various other chemicals may compose the droplets and crystals. On Earth, clouds are formed as a result of saturation of the air when it is cooled to its dew point, or when it gains sufficient moisture from an adjacent source to raise the dew point to the ambient temperature.
Cloudscape over Borneo, taken by the International Space Station
Windy evening twilight enhanced by the Sun's angle, can visually mimic a tornado resulting from orographic lift
Cirrus fibratus clouds in March
High cirrus upper-left merging into cirrostratus right and some cirrocumulus far right