The bases of these clouds form at about metres above sea level. They are usually composed of ice crystals. The bases of these clouds form at about — m above sea level. They are mostly made of water droplets but can contain ice crystals. The clouds are often seen as bluish-grey sheets that cover most, if not all, of the sky.
They can obscure the Sun. The bases of these clouds form at altitudes below m. They are mostly made of drops of water. Wayfinder navigators use clouds to work out where the wind is coming from or if it changes direction so they can trim their sails accordingly.
Like smoke from a haystack, cloud roads follow the wind. A cloud road indicates the wind is coming from the horizon. If the road is straight, the wind is steady — but if you see the road curve, it means that the wind direction will change. The two main type of mid-level clouds are altostratus and altocumulus.
Altostratus clouds over Kentucky Altocumulus sunset 23 Nov. Altostratus clouds are "strato" type clouds see below that possess a flat and uniform type texture in the mid levels. They frequently indicate the approach of a warm front and may thicken and lower into stratus, then nimbostratus resulting in rain or snow. However, altostratus clouds themselves do not produce significant precipitation at the surface, although sprinkles or occasionally light showers may occur from a thick alto-stratus deck.
Altocumulus clouds exhibit "cumulo" type characteristics see below in mid levels, i. Like cirrocumulus , altocumulus may align in rows or streets of clouds, with cloud axes indicating localized areas of ascending, moist air, and clear zones between rows suggesting locally descending, drier air. Altocumulus clouds with some vertical extent may denote the presence of elevated instability, especially in the morning, which could become boundary-layer based and be released into deep convection during the afternoon or evening.
Low-level clouds:. Low-level clouds are not given a prefix, although their names are derived from "strato-" or "cumulo-", depending on their characteristics. Low clouds occur below feet, and normally consist of liquid water droplets or even supercooled droplets, except during cold winter storms when ice crystals and snow comprise much of the clouds. The two main types of low clouds include stratus , which develop horizontally, and cumulus , which develop vertically.
Stratus clouds are uniform and flat, producing a gray layer of cloud cover which may be precipitation-free or may cause periods of light precipitation or drizzle. Low stratus decks are common in winter in the Ohio Valley, especially behind a storm system when cold, dismal, gray weather can linger for several hours or even a day or two.
Stratocumulus NImbostratus. Stratocumulus clouds are hybrids of layered stratus and cellular cumulus, i. Stratocumulus also can be thought of as a layer of cloud clumps with thick and thin areas. These clouds appear frequently in the atmosphere, either ahead of or behind a frontal system. Nimbostratus clouds are generally t hick, dense stratus or stratocumulus clouds producing steady rain or snow.
In contrast to layered, horizontal stratus , cumulus clouds are more cellular individual in nature, have flat bottoms and rounded tops, and grow vertically. In fact, their name depends on the degree of vertical development.
For instance, scattered cumulus clouds showing little vertical growth on an otherwise sunny day used to be termed " cumulus humilis " or " fair weather cumulus ," although normally they simply are referred to just as cumulus or flat cumulus.
A cumulus cloud that exhibits significant vertical development but is not yet a thunderstorm is called cumulus congestus or towering cumulus. If enough atmospheric instability, moisture, and lift are present, then strong updrafts can develop in the cumulus cloud leading to a mature, deep cumulonimbus cloud, i. In addition, cloud electrification occurs within cumulonimbus clouds due to many collisions between charged water droplet, graupel ice-water mix , and ice crystal particles, resulting in lightning and thunder.
Cumulus clouds are all capable of producing some serious storms!!! Other interesting clouds:. Wall Cloud : A localized lowering from the rain-free base of a strong thunderstorm. The lowering denotes a storm's updraft where rapidly rising air causes lower pressure just below the main updraft, which enhances condensation and cloud formation just under the primary cloud base. Wall clouds take on many shapes and sizes.
Some exhibit strong upward motion and cyclonic rotation, leading to tornado formation, while others do not rotate and essentially are harmless. Shelf Cloud : A low, horizontal, sometimes wedge-shaped cloud associated with the leading edge of a thunderstorm?
Although often appearing ominous, shelf clouds normally do not produce tornadoes. Paducah, Ky Winchester, Ky. Fractus : Low, ragged stratiform or cumuliform cloud elements that normally are unattached to larger thunderstorm or cold frontal cloud bases. Also known as scud , fractus clouds can look ominous, but by themselves are not dangerous.
If precipitation falls from stratus clouds, it is usually in the form of drizzle or light snow. Cumulus clouds are large and lumpy. Their name comes from the Latin word meaning "heap" or "pile. Cumulus clouds are created by strong updrafts of warm, moist air. Most forms of heavy precipitation fall from cumulus clouds. The weather they bring depends on their height and size. The higher the base of a cloud is, the drier the atmosphere and the fairer the weather will be.
Clouds located close to the ground mean heavy snow or rain. Variations Clouds are also classified according to how high they are in the atmosphere and what kind of weather they produce.
The prefix "cirro-" refers to clouds that lie more than 6, meters 20, feet above the Earth. The prefix "alto-" indicates clouds whose bases are between 2, and 6, meters 6,, feet above the Earth, such as altocumulus and altostratus clouds. They are considered "mid-level" clouds and are mostly made of liquid water droplets, but can have some ice crystals in cold enough temperatures. The prefix "nimbo-" or the suffix "-nimbus" are low-level clouds that have their bases below 2, meters 6, feet above the Earth.
Clouds that produce rain and snow fall into this category. Nimbostratus clouds bring continuous precipitation that can last for many hours. These low-level clouds are full of moisture.
Cumulonimbus clouds are also called thunderheads. Thunderhead s produce rain, thunder, and lightning. Many cumulonimbus clouds occur along cold fronts, where cool air is forced under warm air. They usually shrink as evening approaches, and moisture in the air evaporate s. Cumulonimbus clouds gradually become stratocumulus clouds, which rarely produce rain. Clouds and Weather Certain types of clouds produce precipitation. Clouds also produce the bolt of electricity called lightning and the sound of thunder that accompanies it.
Lightning is formed in a cloud when positively charged particles and negatively charged particles are separated, forming an electrical field. When the electrical field is strong enough, it discharges a superheated bolt of lightning to the Earth.
Most of what we consider to be single lightning strikes are in fact three or four separate strokes of lightning. The sound of thunder is actually the sonic shock wave that comes when the air, heated by the lightning bolt, expands very rapidly. Thunder sometimes sounds like it comes in waves because of the time it takes the sound to travel.
Because the speed of light is faster than the speed of sound, lightning will always appear before its thunder is heard. Meteorologist s measure cloud cover, or the amount of the visible sky covered by clouds, in units called okta s. An okta estimates how many eighths of the sky octo- is covered in clouds. A clear sky is 0 oktas, while a totally overcast or gray sky is 8 oktas.
Scientists have experimented with a process called cloud seeding for many years. Cloud seeding aims to influence weather patterns. Seeds, or microscopic particles, are placed in clouds. These seeds are artificial cloud condensation nuclei CCN , which are tiny particles of dust , salt , or pollution that collect in all clouds. Every raindrop and snowflake contains a CCN. Water or ice droplets accumulate around CCN.
Scientists hope that cloud seeding will allow people to control precipitation. Extraterrestrial Clouds Clouds exist in outer space. The highest band, at 50 kilometers above the surface of the planet, is mostly clear. These storm clouds appear as bands and swirls of yellow, brown, and red. Most of these clouds are made of droplets of ammonia and ammonia crystals, mixed with phosphorus and sulfur.
These ammonia storms would be toxic on Earth.
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