Jessica Wortmann, age 13, of Erie, Penn., for her question:
HOW MANY KINDS OF CLOUDS ARE THERE?
A cloud is a mass of small water droplets or tiny ice crystals that floats in the air. There are four main families of clouds but these are broken down into various varieties that number more than 100.
The four main families of clouds are high clouds, middle clouds, low clouds and clouds which may extend through all levels.
Clouds are named with Latin words that actually describe their appearance. Cirrus means "curl" or "ringlet of hair." Stratus means "a spreading out." Cumulus means "heap" or "mass." Nimbus means "rain cloud."
Most important high clouds are cirrus clouds. They float five or more miles above the earth and are made of tiny particles of ice. Cirrus clouds are feathery and threadlike and often form long streamers with hooks or tufts at the end.
Cirro stratus clouds, which belong to the same cloud family, form tangled webs or thin whitish sheets. When cirro stratus clouds cover the sky, a large ring or halo is sometimes seen around the sun or moon. This is caused by a blending of rays of light as they pass through ice.
Cirro cumulus clouds look like very small round balls or flakes. Sometimes this type of cloud is called a "buttermilk" or "mackerel" sky.
Middle clouds are called alto stratus and alto cumulus clouds. These clouds are made of little drops of water and are found from about two to four miles above the earth.
Alto cumulus clouds are round puffs of cloud, larger than cirro cumulus clouds. These clouds are made of little drops of water and are found from about two to four miles above the earth.
Alto cumulus clouds are round puffs of cloud, larger than cirro cumulus clouds. They often float in lines, group and ranks. Alto stratus clouds cover the sky with a grayish veil through which the sun or moon may shine as a spot of pale light.
Low clouds are called stratus, nimbo stratus and strato cumulus clouds. They are present at levels less than a mile high and are made of water droplets.
The fourth cloud family includes clouds which build up from low clouds to the very highest levels. They are called cumulus and cumulo nimbus clouds. Cumulus clouds are the dome shaped "woolpack" or "cauliflower" clouds which are seen quite often during the summer. They may be as much as half a mile thick from their flat bases to their rounded tops.
Cumulo nimbus clouds are the thunderstorm clouds. They look like big mountains and are as large as they seem, usually one to three miles thick. Near the Equator they may be as much as eight or nine miles from top to bottom.
Very beautiful but rarely seen clouds are the noctilucent clouds which are 32 to 55 miles high and the nacreous or mother of pearl clouds about 18 miles high. These very thin, wonderfully colored clouds are made of dust or water drops. They may be seen only after sunset or before sunrise and usually only at high latitudes.
When jet airplanes fly at very high altitudes, man made clouds are sometimes seen. These are con trails, or condensation trails. Con trails look very much like ribbons of cirro cumulus clouds and, like these clouds, they are also made of little bits of ice.