Taking time to appreciate the powers at work in the natural environment really does put most human frustration into perspective. It is impossible to worry about minor work deadlines, looming housework, sibling squabbles or DIY problems when faced with the beauty of the countryside. For me, this is particularly true when I venture into expansive natural environments. When confronted with huge skies and far-reaching views, I am gently reminded that I am a tiny cog in the machine that is Plant Earth. And that’s a really good thing.
Contemplating the beautiful skies is one thing, but I am embarrassed to admit that I know little about the classifications of the clouds that drift by. In my world, there’s blue sky and in terms of clouds there are three main types: fluffy white ones, long thin ones left by planes, and dark looming ones that mean I need to be ready with the waterproofs. There are words I have heard other people use – cumulus, cirrus, nimbus (or is that a Harry Potter broom?!), stratus – but I wouldn’t be able to identify them.
Time to change that, I think, and the perfect reference guide has just been published. The World Meteorological Organisation has released a new, digitised version of its International Cloud Atlas, the global reference book for meteorologists and sky-watchers alike. It's the first update for the atlas since 1987 and the first version to be fully web-based. There’s lots of detail but also some general basics. There are 10 basic genera of clouds (including many of the words I was floating earlier, so I’m not totally put to shame!) - cirrus, cirrocumulus, cirrostratus, altocumulus, altostratus, nimbostratus, stratocumulus, stratus, cumulus and cumulonimbus. Then within each genus, there are several species and varieties that describe the exact character of the cloud.
To keep it simple, I’ve pulled out a few examples (both traditional cloud types and specialist ones that have been included for the first time in this new guide) that you might want to try spotting on your travels…
Ask a child (or me!) to draw a cloud and they would draw Cumulus. The official definition is: Detached clouds, generally dense and with sharp outlines, developing vertically in the form of rising mounds, domes or towers, of which the bulging upper part often resembles a cauliflower. The sunlit parts of these clouds are mostly brilliant white; their base is relatively dark and nearly horizontal.
This is a form of cloud that most walkers are good at recognising, as it signals time to grab your waterproofs or make a dash for the nearest watering hole. The official definition is: A grey cloud layer, often dark, the appearance of which is rendered diffuse by more or less continuously falling rain or snow, which in most cases reaches the ground. It is thick enough throughout to blot out the sun.
These, in my book, are the most beautiful and magical form of cloud. Perhaps it is just that wisps remind me of a childhood favourite, Willo The Wisp. Cirrus clouds are defined as: Detached clouds in the form of white, delicate filaments or white or mostly white patches or narrow bands. These clouds have a fibrous (hair-like) appearance, or a silky sheen, or both.
And now to the new specialist examples…
This type of cloud develops locally in the vicinity of large waterfalls as a consequence of water broken up into spray by the falls. The downdraft caused by the falling water is compensated for by the locally ascending motion of air. These special clouds are given the name of the appropriate genus followed by the special cloud name Cataractagenitus (for example, Cumulus Cataractagenitus).
The latest cloud atlas acknowledges that human activity (such as aeroplanes, fires and industrial activity) create specific types of cloud. Clouds that have originated specifically as a consequence of human activity are given the name of the appropriate genus, followed by the special cloud name homogenitus. Aircraft condensation trails (contrails) that have persisted for at least 10 minutes are given the name Cirrus Homogenitus.
The full cloud atlas is available online at https://www.wmocloudatlas.org/home.html and is well worth a browse if you fancy broadening your cloud knowledge.
5 June 2017
(Images courtesy of cloud atlas and the iFootpath Facebook community)