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Cloud and Fog

Fog

Sea fog

Cloud

Introduction

Cloud forms when moisture is cooled, much the same way as if on a cold day you breathe out and see a cloud of your breath Howevere clouds can tell us alot about what is going on in the atmosphere, by it's shape, the height it which it forms, and where it moves from and to.

Classification of Clouds

According to the World Meteorological Organisation[1] the present international system of Latin-based cloud classification dates back to 1803, when amateur meteorologist Luke Howard wrote The Essay on the Modifications of Clouds.

There are ten basic cloud “genera,” which are defined according to where in the sky they form and their approximate appearance. The new International Cloud Atlas has made no additions to these 10 genera.

High-level clouds typically have a base above about 5 000 metres (16 500 feet); middle-level clouds have a base that is usually between 2 000 and 7 000 m (6 500 to 23 000 feet); and low-level clouds usually have their base at a maximum of 2 000 m (6 500 feet).

Most cloud names contain Latin prefixes and suffixes which, when combined, give an indication of the cloud’s character. These include:

  • Alto: mid-level (though Latin for high)
  • Cirrus/cirro: feathers, wispy
  • Cumulus/cumulo: heaped up/puffy
  • Nimbus/nimbo: rain-bearing
  • Stratus/strato: flat/layered and smooth

The 10 genera are subdivided into “species,” which describe shape and internal structure, and “varieties,” which describe the transparency and arrangement of the clouds. In total there are about 100 combinations.

The International Cloud Atlas

The International Cloud Atlas was first published in the late 19th century. It contains a detailed manual of standards and numerous plates of photographs of clouds and certain other weather phenomena. It is the world reference for observing and classifying clouds and other weather phenomena. The Atlas contains pictures, definitions, and explanations that are accepted and used by all WMO’s 191 Member countries and territories. [1]

Source References:

  1. ↑ Jump up to:1.0 1.1 World Meteorological Organisation
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