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9.12 Clouds and Precipitation

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Cloud Groups

Cloud types are divided into three groups, high, middle and low level. The different types of clouds in the atmosphere are classified into a system that uses Latin words to describe their appearance and the height of the cloud base. This classification was developed by the English chemist Luke Howard in 1803. The Latin words used are: cirrus which means "curl of hair"; the prefix “alto” means middle level; stratus which means "layer"; cumulus which means "heap"; and nimbus which means "rain".

Cumulus: formed cloud develop vertically in the form of heaped or towering mounds which often resemble a cauliflower. The parts of the cloud that are lit-up by the sun are mostly brilliant white. While their bases are nearly always horizontal and are relatively dark due to the larger water droplets been held up by rising currents of air and are extremely unstable.

Stratus: Stratus cloud look grey and develop in horizontally layers forming sheets of clouds, their bases are fairly uniform and sometimes they appear in ragged patches. Stratus cloud indicates stable layers of air and smooth flying conditions.