New International Cloud Atlas – beauty of the sky (3 min reading)

“Behind every cloud is another cloud” 🙂

Dear readers,

For those of you who are interested in weather and meteorology, the World Meteorological Organization (WMO) has released its new, long-awaited, digitized International Cloud Atlas – the global reference for observing and identifying clouds, which are an essential part of weather, the climate system and the water cycle. It was released for the World Meteorological Day on 23rd March.

The new Atlas combines 19^th century traditions with 21^st century technology. It contains hundreds of images submitted by meteorologists, photographers and cloud lovers from around the globe.

It includes new classifications, including volutus, a roll cloud; clouds from human activities such as the contrail, a vapour trail sometimes produced by airplanes; and asperitas, a dramatic undulated cloud which captured the public imagination. It also features meteorological phenomena like rainbows, halos, snow devils and hailstones.

Classification of Clouds

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 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.

High-level clouds typically have a base above about 5 000 metres; middle-level clouds have a base that is usually between 2 000 and 7 000 m; and low-level clouds usually have their base at a maximum of 2 000 m.

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

Cirrus