Posted by: pyeager | July 1, 2009

More on New Cloud Type–Altocumulus Undulatus Asperatus

Since the talk of a possible new cloud type (New Cloud–Altocumulus Undulatus Asperatus) has started, a couple of people have asked me whether I thought the new cloud type was truly a new cloud and whether it might be a reflection of global warming.

Not a New Cloud–But Will Be Photographed More Often

The “new cloud” is a type of cumulus cloud that appears on days when the atmosphere is particularly unstable. On days like this, the clouds in the sky change quickly. Watch the sky when thunderstorms are in the forecast, and you can see towering cumulus clouds change before your eyes. If you watch the sky for as little as 30 minutes, the sky might look dramatically different  when you’re finished than it did when you started.

Days such as these are when the so-called Altocumulus Undulatus Asperatus cloud appears, so it disappears as quickly as it forms, making it difficult to capture on film.

Now, though, that we’re more aware of this type of cloud, a greater number of people will be looking for this cloud formation, resulting in a significant increase in the photographs, especially now that photographing the sky for many of us is as easy a pulling out our phones.

No Tie to Global Warming

Obviously, since I don’t think this is a new cloud formation, I don’t think the cloud is associated with global warming.

While I was relieved to see that the new cloud is not being widely discussed in association with global warming on the Internet (like so many weather items not related to global warming are), I have seen a couple of “experts” comment that it’s clear that a cloud this menacing looking must need to have “a lot of heat” in order to be created.

There is no meteorological basis for such a statement. The menacing nature of the cloud is related to its underside being rough (images can be seen here), which is not logically related to extra heat in the atmosphere. Concentrated heat in the atmosphere results in towering clouds with relative flat bottoms (thunderstorm clouds), not clouds with rough bottoms.

Dry air interacting with the bottom of a cloud will result in a ragged appearance, and wind blowing parts of the cloud to pieces will result in a ragged cloud.

It’s most likely not a new cloud, and it’s not associated with global warming.

–Paul Yeager

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