Clouds and the man who named them
Often admired as they drift across the sky, clouds come in all sorts of shapes and sizes, with each type associated with a particular type of weather.
Clouds are a huge collection of very small water droplets and ice crystals, that sit above the earth’s surface and drift around in the wind.
They form due to air rising, cooling and condensing. This occurs in two main ways – mass ascent and convection.
Mass ascent is where large bodies of air are forced to rise, such as when warm air and cold air collide. This is how weather fronts form, with huge bands of cloud as a result.
Convection is a more localised process, when the sun heats the ground and causes bubbles of warm air to become buoyant. They then rise upwards, eventually cooling and condensing to form discrete blobs of cloud.
How did clouds get their names?
Cumulonimbus, stratus, cirrus, altocumulus castellanus – all different types of clouds. But who gave them their names?
The classification of clouds is based upon work by Luke Howard (1772-1864), who lived in London and was a pharmacist and amateur meteorologist.
It basically identified clouds with reference to their height in the sky; low, medium and high, as well as their appearance; layered (stratus), heaped (cumulus) or hair-like (cirrus).
His work resulted in meteorologists around the world contributing to this further and led to the first edition of the International Cloud Atlas in 1896 – something that’s still in use today.
Classification of clouds
The International Cloud Atlas classifies clouds in terms of genera, species and varieties, which allows a detailed depiction of their appearance.
Genera describes the 10 main cloud groups that are most commonly known and used;
Stratus (St), Stratocumulus (Sc), Cumulus (Cu), Cumulonimbus (Cb)
Altocumulus (Ac), Altostratus (As), Nimbostratus (Ns), (Nimbostratus extends to other levels)
Cirrus (Ci), Cirrocumulus (Cc), Cirrostratus (Cs)
Varieties denote a cloud’s special features in how it looks, in addition to the degree of transparency present. Cloud that has a wave-like appearance or is undulating, would be termed undulatus.
So, the next time you stare up at the sky and look at the clouds, with the help of the Met Office cloud spotting guide, see if you can work out what type of cloud it is.