Bruce Vandemater, age 11, of iiarcy, New York, for his question:
What is a cumulonimbus cloud?
No two clouds are alike and what's more, they change from moment to moment. You would thinly that naming and classifying them is downright im¬possible. Nevertheless, the job has been done. An English school teacher made a start by sorting cloud types into three classes. Later, extras were added to his original terms and one cloud type was named the cumulonimbus.
A cumulonimbus is a stupendous cloud that comes with spectacular light¬ing effects and resounding orchestration. It tends to build up on sultry summer days and when it reaches its full fury, sensible people scurry for shelter. It is, of course, a thunderhead cloud that becomes a thunder¬storm, accompanied by lightning and roaring thunder.
Way back in 1803, Luke Howard sorted the various clouds into three main types. In those days, meteorologists did not know a great deal about the nature and formation of clouds so he gave them names that seemed to suit what they looked like. Howard was a school master and he used names de¬rived from Latin words that could be understood by scholars of different countries.
The term "stratus" means a flat layer. Stratus clouds~are those that hang in fiat curtains across the sky. Often they are glowering grey rain¬clouds, though this fact was not noted at the time. The term "cirrus" means a curl. Cirrus clouds are those thin, wispy white curls that drift high in the sky. Often they catch the long, slanting rays of the rising or setting sun and reflect them in spendid colors.
The term "cumulus" means a heap. Surely it is a suitable name to describe those fluffy white cauliflower clouds that drift lazily across a blue summer sky. Ah, but these innocent looking cumulus clouds can pile up in a head and become a rowdy cumulonimbus.
The three basic terms describe more or less what the three major cloud types. look like. Later, meteorologists wanted names that describe more about how various cloud types are likely to behave themselves. Two extras were added. "Alto" means that the cloud is fairly high above tile ground. "Nimbus" means that a cloud is likely to shed rain.
For example, altostratus clouds are flat layers high in the sky. They may look like thin gauzy veils of pale blue or grey and sometimes their fine particles reflect halos around the sun. Nimbostratus clouds are flat grey layers, heavy with rain. Altocumulus clouds are high flying heaps of bulging white mist. On sultry summer days they pile up in a huge, flat topped thunderhead alias a cumulonimbus.
The "cumulo" part of this weatherman's term means that the cloud was formed from a heap of summery cumulus clouds. The "nimbus" means that the turbulent monster is likely to rain which it surely does. Tao mention is made of its dramatic sound and lighting effects. But a cloud of this type is a mighty little storm, teeming with turbulent energy. Its wild winds, contrasting pockets of warm and cool, light and heavy air are sure to generate flashes of lightning and claps of rolling thunder.