CLOUDS
The atmosphere always contains in greater or smaller amounts tiny particles, such as dust from roads, desert sand, plant pollen, salt particles from oceans, and factory smoke. These fragments are hygroscopic "particles that readily absorb moisture." A cloud is merely a mass of hygroscopic nuclei that have soaked up moisture from the air.
The heat generated by the Sun's energy causes earthbound moisture to evaporate (turn into water vapor). Water vapor is one of the gases that make up the atmosphere. Water vapor is lighter than air, and it rises. If the air it passes into is cold the vapor condenses, and turns back into moisture. The water droplets that come from this process cling to the hygroscopic nuclei. These water-soaked nuclei bunched together form a cloud. Fog is the same principle but it's a cloud on the ground.
Changes in atmospheric conditions account for the different shapes of clouds and for
their presence at various altitudes. Formations of the clouds give a clue on the forces at play in the atmosphere.
CIRRUS (CI) clouds are detached clouds of delicate and stringy appearance, white in color, without shading. They appear in varied forms, isolated tufts, lines drawn across the sky, branching featherlike plumes, and curved lines ending tufts.
Cirrus clouds are composed of ice crystals. Before sunrise and after sunset, cirrus clouds may still be colored bright yellow or red. Being high-altitude clouds, they light up before lower clouds and fade out much later. Cirrus clouds indicate the direction in which a storm may lie.
CIRROCUMULUS (CC) Cirrocumulus clouds are commonly called "mackerel sky" look like rippled sand,or like cirrus clouds containing globular masses of cotton. Cirrocumulus clouds are a indication that a storm is probably approaching.
CIRROSTRATUS (CS) Cirrostratus clouds are a thin whitish veil which does not blur the outlines the Sun or Moon, but gives rise to halos (colored or whitish rings and arcs around the Sun or Moon, the colored arcs apear reddish on the inside edges.) A milky veil of fog (thin stratus) lnd altostratus are distinguished from a veil or cirrostratus of similar appearance by the halo phenomenon, which the Sun or Moon nearly always produces in a layer of cirrostratus. The appearance of cirrostratus is a good indication of rain.
ALTOCUMULUS (AC)
Altocumulus clouds are a layer (or patches) composed of flattened globular masses, the smallest elements of the regularly arranged layer being fairly small and thin, with or without shading. The balls or patches usually are arranged in groups, in lines, or in waves. Sometimes a corona (similar to a halo but with the reddish color on the outside edges) may be seen on the altocumulus. This cloud form differs from the cirrocumulus by generally having larger masses, by casting shadows, and by having no connection with the cirrus forms. When followed by cirrocumulus, a thunderstorm is nearing.
ALTOSTRATUS (AS)
Looking like a thick cirrostratus, but without halo phenomena, the altostratus is a fibrous veil or sheet, gray or bluish in color. Sometimes the Sun or Moon is obscured completely. At other times they can be vaguely seen, as through ground glass. Light rain or heavy snow may fall from a cloud layer that is definitely altostratus.
NIMBOSTRATUS (NS)
Nimbostratus clouds are a dark gray colored amorphous (shapeless) and rainy layer of cloud. They usually are nearly uniform and feebly illuminated, seemingly from within.
When precipitation occurs, it is in the form of continuous rain or snow, but nimbostratus may occur without rain or snow. Often there is precipitation that does not reach the ground; in which cases, the base of the cloud usually looks wet because of the trailing precipitation.
In most instances the nimbostratus evolves from an altostratus, which grows thicker and whose base becomes lower until it becomes a layer of nimbostratus. When precipitation falls continually, the base of the cloud may extend into the low cloud family range.
STRATOCUMULUS (SC)
Stratocumulus clouds are a layer (or patches) of clouds composed of globular masses or rolls. The smallest regularly arranged elements are fairly large. they are soft and gray, with dark spots.
Underneath stratocumulus waves or strong winds occur. Under the thick parts up-currents rise. Above the cloud layer the air is smooth, but it is turbulent below.
STRATUS (ST)
Stratus clouds are a low uniform layer of clouds, resembling fog, resting on the ground. A veil of stratus sky gives a hazy appearance. Usually, only drizzle is associated with stratus. When there no precipitation, the stratus cloud form drier than other similar forms, and it shows some contrasts and some lighter transparent parts. CUMULUS (CU)
Cumulus clouds are dense clouds with vertical development. Their upper surfaces are dome-shaped and exhibit rounded projections, and their bases are horizontal. Stratocumulus clouds resemble ragged cumulus clouds in which the parts show constant change. Strong updrafts exist under and within all cumulus formations.
CUMULONIMBUS (CB)
Cumulonimbus clouds are heavy masses of cloud, with towering vertical devlopment, whose cumuliform summits resemble mountains or towers. Their upper parts
have a fibrous texture, and often they spread out in the shape of an anvil.
Cumulonimbus clouds are generally associated with showers of rain or snow, and sometimes produce hail. They often are associated with thunderstorms.
Most of the cloud types are shown at their average height. The bases of the cumulonimbus may be anywhere from 1600 feet to 6500 feet. Although you would never see all types at anyone time in nature, you may observe two or three layers of clouds of different types at one observation.
