Why Do Clouds Vary in Shape?
Clouds vary in shape according to their height and temperature, and they contain minute drops of water or ice particles or a combination of both. And, of course, their formation is greatly affected by wind changes. There are basically three groups of clouds: high clouds between 17,000 and 45,000 feet (cirrus, cirro-cumulus and cirro-stratus); middle clouds between 7,000 and 23,000 feet (alto-cumulus, alto-stratus and nimbo-stratus); and low clouds up to 7,000 feet (strato-cumulus, stratus, cumulus and cumulo-nimbus).
Their height and temperature decide how much pressure is exerted on them by the atmosphere. Finally, the shapes of clouds differ according to the time of day. Towards evening clouds tend to thin out, rise a little and flatten out. Now there are special clouds too. Let us know about these special types of clouds, how they are formed, and what they indicate about the weather.
- Mammatus clouds are low hanging bulges that droop from cumulonimbus clouds. Mammatus clouds are usually associated with severe weather.
- Lenticular clouds are caused by a wave wind pattern created by the mountains. They look like discs or flying saucers that form near mountains.
- Fog is a cloud on the ground. It is composed of billions of tiny water droplets floating in the air. Fog exists if the atmospheric visibility near the Earth’s surface is reduced to 1 kilometer or less.
- Contrails are condensation trails left behind jet aircrafts. Contrails form when hot humid air from jet exhaust mixes with environmental air of low vapor pressure and low temperature. The mixing is a result of turbulence generated by the engine exhaust.
- Fractus clouds are small, ragged cloud fragments that are usually found under an ambient cloud base. They form or have broken off from a larger cloud, and are generally sheared by strong winds, giving them a jagged, shredded appearance. Fractus have irregular patterns, appearing much like torn pieces of cotton candy. They change constantly, often forming and dissipating rapidly. They do not have clearly defined bases. Sometimes they are persistent and form very near the surface.
- Green Clouds are often associated with severe weather. The green color is not completely understood, but it is thought to have something to do with having a high amount of liquid water drops and hail inside the clouds. In the Great Plains region of the U.S. green clouds are associated with storms likely to produce hail and tornadoes.