James Brown, age 14, of Houston, Texas, for his question:
How many cloud types does a weatherman recognize?
The nations of the world often disagree over the most unlikely items. But in weather problems, which know no boundaries, there is no disagreement. Almost all the nations of the world, in fact, unite their efforts to solve the mysteries of the global weather turmoil. To do this, they must agree on scientific terms for weather events. For a long time, the international meteorologists have been using ten cloud categories.
The first cloud classification was suggested in 1803 by Luke Howard, an Englishman. He separated the countless clouds into three categories. He named the fluffy white cauliflower clouds cumulus clouds and the flat, greyish types stratus clouds. He named those small, fine feathery types cirrus clouds. As meteorologists learned more, they subdivided Howard's three cloud types.
The International Meteorological Committee published the first global cloud classification in 1896. With a few improvements, we still use its ten categories. Altocumulus, Cumulonimbus, cirrostratus and nimbostratus may sound like words from a Martian dictionary but with a few small clues they are as easy to read as a thermometer.
Howard's three basic terms are in all the cloud names. A nimbostratus is a stratus cloud with the threat of rain. Any cloud term with the affix nimbo means that it is either raining or heavy with rainy threats. The cumulonimbus is a thunderhead, a pile of cumulus clouds ready to douse a storm. The prefix alto means high altocumulus and altostratus are high cumulus and high stratus clouds.
Clouds are forever changing from one form to another and some of the terms are formed from two of the basic three. Cirrostratus are higher thin clouds that cover the sky with gauzy veils.
Cirrocumulus are the high, little white puffs that form a so called mackerel sky. Stratocumulus spread masses of torn grey rags over the sky.
These are the ten cloud categories used by the modern meteorologists. Recently the prefix fracto has been used to give an extra clue to the nature of a cloud. It means torn or fragmented. When the weatherman adds this prefix to one of the ten accepted terms he is describing a wind blown cloud and in its changeable life, almost any cloud can be torn to fragments by the breezes.
Clouds can be classed in four heights low, medium, high and towering. Stratus, nimbostratus and stratocumulus are low clouds hovering about 6,500 above ground. Altostratus and altocumulus are medium high clouds, beginning about 10,000 feet. Cirrus, cirrocumulus and cirrostratus are high clouds ranging from 20,000 to 25,000 feet. The towering cumulonimbus may hold its flat head ten miles or more above the ground.