Cumulus clouds against a blue sky. These cumulus mediocris clouds have a moderate size and are about as tall as they are wide. Cumulus clouds typically occur under 2000 metres altitude. They form from water vapour in rising columns of air which condenses as it cools. Cumulus clouds often form at cold fronts where the advancing,cool air forces warm air upwards. The mediocris variety generally occurs when there is moderate heat transfer (convection) in the atmosphere,and are most common in the late morning or early afternoon. Cumulus mediocris clouds are generally too small to produce rain. This cloud type occurs over most areas of the world | |
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Crédit: | Science Photo Library / Mead, John |
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