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Glossary |
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C |
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Carbon dioxide |
A gas (CO2) present in the atmosphere which plays an important role in the greenhouse effect. | |
Celsius temperature scale |
Thermodynamic scale of temperature. Temperature in degrees Celsius can be obtained
from value in degrees Fahrenheit by the following formula:
C = (F - 32) x 5/9 |
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Chlorofluorocarbons |
Chemicals that release chlorine atoms that destroy ozone high in the atmosphere. An animation of the process may be viewed by clicking here. | |
Cirrus cloud |
High cloud, delicate, hair-like and feathery looking. | |
Climate |
The atmospheric conditions for a long period of time, and generally refers to the normal or mean course of the weather. Includes the future expectation of long term weather, in the order of weeks, months or years ahead. Click here for more information. | To top |
Cloud |
Mass of water droplets or ice crystals caused by water vapor in the atmosphere
condensing or freezing. See Fig. 1 below for an animation and explanation of how
clouds form over mountains.
Fig. 1 As air flows against and over a mountain range, it cools as it rises. The water vapour in the rising air condenses into droplets and forms clouds. When the droplets are large enough they may fall as rain. Most clouds are formed by the ascent and consequent cooling of air to the point of saturation. When the air is saturated, further cooling results in the appearance of liquid water particles and/or tiny ice crystals. See the Clouds page for more detail and the four ways in which moist air can be lifted to form clouds. |
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Cloud cover |
Forecasting terms
Forecasts of cloud cover normally give an average, if no significant variations are expected. A clear day, for example, may at some times see a few cloud patches. Forecasters expecting significant variations in cloud amount may use such terms as sunny periods, sunny breaks, cloudy periods, cloudy at times, mostly/mainly sunny, mostly/mainly cloudy. If expecting a major change in cloud cover, they usually indicate a distinct trend, e.g. becoming sunny or cloud increasing. |
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Cold Fronts |
See Fronts (Cold). | |
Condense |
Change from a gas to a liquid. | |
Contract |
To reduce in size. | |
Convection |
The process generally associated with warm rising air and the formation of cloud. Local breezes, wind and thunderstorms are a result of convection in the atmosphere. | |
Cumulonimbus cloud |
Heavy, puffy, heaped, dark cloud of great vertical depth, often bringing rain. Some have a distinctive anvil shaped head. | |
Cumulus |
Clouds with a woolly, heaped appearance that often produce rain. | |
Cyclogenesis |
The rapid development of a low or intensification of a pre-existing one | |
Cyclone |
Atmospheric circulations that rotate clockwise in the southern hemisphere, and anti-clockwise
in the northern hemisphere. Cyclones are areas of lower pressure and generally
associated with stronger winds, unsettled conditions, cloudiness and rainfall. See also Tropical cyclones under for more information. |
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