Types of clouds[PDF]
According to the World Meteorological Organization's International Cloud Atlas, more than 100 types of clouds exist.
Clouds are usually classified under 3 groups depending on the height:
- Low-level clouds (cumulus, stratus, stratocumulus) that lie below 6,500 feet (1,981 m)
- Middle clouds (altocumulus, nimbostratus, altostratus) that form between 6,500 and 20,000 feet (1981–6,096 m)
- High-level clouds (cirrus, cirrocumulus, cirrostratus) that form above 20,000 feet (6,096 m)
Cumulus clouds are rounded, puffy, and a brilliant white when sunlit, while their bottoms are flat and relatively dark. Cumulus clouds develop on clear, sunny days when the sun heats the ground directly below (diurnal convection).
Stratus clouds hang low in the sky as a flat, featureless, uniform layer of grayish cloud. They resemble fog that hugs the horizon (instead of the ground).
Stratocumulus clouds are low, puffy, grayish or whitish clouds that occur in patches with blue sky visible in between. When viewed from underneath, stratocumulus have a dark, honeycomb appearance.
Altocumulus clouds are the most common clouds in the middle atmosphere. You'll recognize them as white or gray patches that dot the sky in large, rounded masses or clouds that are aligned in parallel bands. They look like the wool of sheep or scales of mackerel fish—hence their nicknames "sheep backs" and "mackerel skies."
Altocumulus and stratocumulus are often mistaken. Besides altocumulus being higher up in the sky, another way to tell them apart is by the size of their individual cloud mounds. Place your hand up to the sky and in the direction of the cloud; if the mound is the size of your thumb, it's altocumulus. (If it's closer to fist-size, it's probably stratocumulus.)
Nimbostratus clouds cover the sky in a dark gray layer. They can extend from the low and middle layers of the atmosphere and are thick enough to blot out the sun.
Altostratus appear as gray or bluish-gray sheets of cloud that partially or totally cover the sky at mid-levels. Even though they cover the sky, you can typically still see the sun as a dimly lit disk behind them, but not enough light shines through to cast shadows on the ground.
Cirrus clouds are thin, white, wispy strands of clouds that streak across the sky. Because cirrus clouds appear above 20,000 feet (6,096 m), which is an altitude where low temperatures and low water vapor exist, they are made up of tiny ice crystals rather than water droplets.
Cirrus is Latin for "curl of hair".
Cirrocumulus clouds are small, white patches of clouds often arranged in rows that live at high altitudes and are made of ice crystals. Called "cloudlets," the individual cloud mounds of cirrocumulus are much smaller than that of altocumulus and stratocumulus and often look like grains.
Cirrostratus clouds are transparent, whitish clouds that veil or cover nearly the entire sky. A dead giveaway to distinguishing cirrostratus is to look for a "halo" (a ring or circle of light) around the sun or moon. The halo is formed by the refraction of the light on the ice crystals in the clouds, similarly to how sundogs form but in an entire circle rather than just on either side of the sun.
Cumulonimbus clouds are one of the few clouds that span the low, middle, and high layers. They resemble the cumulus clouds from which they grow, except they rise into towers with bulging upper portions that look like cauliflower. Cumulonimbus cloud tops are usually always flattened in the shape of an anvil or plume. Their bottoms are often hazy and dark.
- VID 150259 - Creation
DATE OF SUBMISSION
- 14:55, 10 January 2020
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