WeatherMatrix (Jesse Ferrell)

A New Cloud For My B-Day? You Shouldn't Have...

By Jesse Ferrell, Meteorologist/Community Director
6/12/2009, 4:10:21 AM

UPDATE: This article says that the picture that spurred the debate was taken in Iowa in 2006, and has some quotes from some disbelieving meteorologists. Meanwhile, the "Asperatus" clouds appeared in Massachusetts Wednesday and Dallas Wednesday night.

ORIGINAL ARTICLE: One of our in-house meteorologists passed me this article saying that a new cloud type (the first in over 50 years) may be created by the World Meteorological Organization (WMO), based on a request from a cloud photographer in the United Kingdom who formed the Cloud Appreciation Society. I thought this was a good article to put up on my birthday because (if these people are right) nature has given us a brand new present.

You can view examples of the proposed "Asperatus" cloud that the Cloud Appreciation Society have captured on this page. They seem to insinuate that this type of cloud has only been seen since 2006 - but below is an example from the Photo Gallery in 2004.


I wonder if it's not the cloud, but just the number of people with easy-to-use digital cameras and Internet connections that has increased in frequency. That said, I hadn't ever photographed anything like it until this year 2006 (see below) and I've been taking cloud pictures since the early 1980s (nearing 10,000 photos on my digital camera since 2006).


Classifying clouds is not easy. 95% of the time what you see in the sky is a combination of several cloud types and even the same cloud may change types at different heights as it morphs over time. It's actually not a new cloud type that the Cloud Appreciation Society is recommending -- not another stratus, cumulus, or cirrus. What they are suggesting is a new "variety" (also called "species" by the Cloud Atlas site) -- which is appended to the cloud type name, which is a much more reasonable request, I think. They say:

We propose that asperatus should be adopted as a new 'variety' of cloud, meaning that it is a particular characteristic that appears in one or other of the main cloud types. This would mean that the rough and choppy looking Altocumulus cloud shown here would become known as 'Altocumulus asperatus'.

I think the biggest problem they are going to have is separating them from the "Undulatus" classification -- for example Stratocumulus Undulatus" (specific examples at Flickr) or "Altocumulus Undulatus" (specific examples at Cloud Atlas on Page 1 & 7) which is how I believe these clouds have typically been classified in the past. The differentiator may be that so-called Asperatus Clouds don't have the look of separate lines or streets, though they are sometimes associated with waves... for example this video on YouTube which shows a gravity wave (or as some Commenters point out, maybe pressure waves instead) would seem to show the so-called Asperatus...

...and the time-lapse movie and photos that I took below in March here show possible Asperatus in waves which are probably orographic (caused by our local mountains).



Other possible "Asperatus" clouds I have photographed:

- 4/30/09 - 5/15/07 - 10/7/06 - 9/30/06

There's one thing I'm fairly certain of - how these clouds form. That's because I took the photographs above on March 25, 2009 under very specific conditions. We had very low humidity, around 25%, but rain was moving in on the radar and disappearing over us (in fact the single-site radars said it was raining over me at the time, but of course they are looking in the clouds, not on the ground). This must be what happens in those sort of situations when there is a stark contrast in humidity and perhaps temperature - while in more "normal" meteorological conditions, virga results.

In any case, I wish the Cloud Appreciation Society luck, I think they might be on to something here. Have you seen these clouds? Upload your photos to the Photo Gallery today! Stay tuned next week, we'll have a video interview with someone from the Cloud Appreciation Society!

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WeatherMatrix (Jesse Ferrell)