Asperatus clouds

While I was away I'd received an email letting me know that a small population of autumn lady's-tresses Spiranthes spiralis had been discovered on a local nature reserve, the first record round Peterborough for a very long time. So, once the first band of showery rain had passed, I headed out to find them. This exquisite little orchid (see extra) is only about 10 cm tall, but is perfectly formed, its white flowers spiralling neatly up the single stem. By midday I was sure that I had my blip in the bag!

I took the opportunity to walk round the rest of the reserve, but decided that it was prudent to return to the car when I heard the first distant rumble of thunder. I made the right decision, as much of the rest of the afternoon was marked by a series of thunderstorms with bouts of torrential rain. However, for about half an hour between two storms, there was a fine display of asperatus clouds, the first I've observed locally. 

In 2009 the Cloud Appreciation Society proposed that these distinctive clouds should be added to the official classification system. The cloud looks a little like the surface of the sea on a choppy day, which is why they proposed that it should be called asperatus from the Latin verb ‘aspero’, meaning to make rough. The term was used by Roman poets to describe the sea as it was roughened by the cold north wind. Soon, the term was being adopted by cloudspotters around the world. But it could only be accepted as an official term. if it were acknowledged by the World Meteorological Organisation in Geneva, who publish the rather dry but thorough bible of cloud classification, The International Cloud Atlas.

For asperatus to stand a chance of becoming official, it would be necessary to have some idea of the atmospheric conditions that cause it to appear. This was provided by an M.Sc. thesis by Graeme Anderson, which found that asperatus is formed in the sort of conditions that produce mammatus clouds, but when the winds up at the cloud level cause it to be sheared into wavelike forms known as undulatus. The conclusion was that there was a case for this being accepted as a new classification – one that is called a cloud ‘supplementary feature’.The Royal Meteorological Society is now encouraging the international meteorological community to update the Cloud Atlas and include asperatus to make it official. If asperatus is accepted, it will be the first official cloud classification in 60 years.

So all in all quite an interesting day, and a perfect way to celebrate reaching 2000 blips!! As ever, thanks to everyone who continues to drop by and sprinkle comments and stars, despite my lack of interaction...