Looking at clouds
Three types of cloud
The sketch sequence
Cirrus: cold, high level clouds, made up of ice crystals, and often having the appearance of tangled fibres or sheaves
Cumulus: Cauliflower-shaped clouds, with individual, generally shortlived towers separated by clear air
Stratus: Cloud covering an extensive area in a uniform, rather featureless layer
Thermal: A mass of warm, buoyant air, formed near the ground which then breaks away from the ground and rises upwards.
Troposphere: The abrupt transition from the troposphere to the overlying stratosphere. It marks the top of many deep clouds
Unstable: A term used to describe atmospheric conditions in which cumulus clouds form. The temperature drops with height so rapidly that masses of air displaced upwards are buoyant and continue moving upwards
Zenith: The point in the sky vertically above the observer
Ross Reynolds, Philip's Guide to the Weather, pub. Phillip's, 01/08/1999 www.amazon.co.uk
Ian James is Professor of Geophysical Fluid Dynamics and Head of Mathematics, Meteorology and Physics at the University of Reading. He has written numerous papers and a graduate level text book on the low frequency variability of atmospheric flow and on the circulation of planetary atmospheres. He is ordained priest in the Church of England and is Environment Advisor to the Bishop of Oxford.