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News & ArtsMonday, November 21, 2011
Science The Mystery of Discrete Clouds
Posted by Charles Mudede on Mon, Nov 21, 2011 at 9:10 AM
Something I failed to include in my feature Cloud Appreciation Society is this comment made by Dr. Gerald Pollack, a UW professor of bioengineering, at the opening of this marvelous lecture:
Think about the cloud. The water evaporates from the sea... and it moves up. And the thought is that this water should have spread uniformly over the sky. And yet somehow it doesn't quite. The water vapor actually coalesces into discrete clouds. Now why is that? How come the humidity inside the cloud is 100 percent and right next to it, it is practically zero? How come we don't know the answer to that?It's astonishing that we do not know everything about clouds. Indeed, the most obvious aspect of a cloud (what makes it a cloud and not a cloud) is still a mystery. One day we will have the answer to everything.
4
I've looked at clouds from both sides now,
From up and down, and still somehow
It's cloud illusions I recall.
I really don't know clouds at all.
http://www.youtube.com/watch?v=KR5ELDYcP…
From up and down, and still somehow
It's cloud illusions I recall.
I really don't know clouds at all.
http://www.youtube.com/watch?v=KR5ELDYcP…
6
Clouds are a process, not discrete objects. "Clouding" occurs where the conditions favor water-droplet condensation. We don't have *any* meteorological feature spread evenly across the sky, so to pose that as a real question is idiotic. Clearly (haha) weather patterns occur in pockets and streams of warm or cool air, with differential humidity, engaging in dynamic interactions.
Speaking of cool cloud processes, did anyone else see the very long-tailed lenticular cloud streaming east of Mt. Rainier yesterday? It looked like a standing wave. Quite neat.
Speaking of cool cloud processes, did anyone else see the very long-tailed lenticular cloud streaming east of Mt. Rainier yesterday? It looked like a standing wave. Quite neat.
10
This talk isn't about cloud physics--it is about long-range order in water structure near surfaces. The physics of water molecules on the molecular level is really hard to study and we don't have a good model that behaves like we know water behaves over wide ranges of conditions. Am I the only one who actually listened to the talk? But even if it were about cloud formation, asking basic questions about cloud formation is not dumb while hand-waving responses on complicated physics ARE dumb. This is a pretty good paper on it: http://www.sciencemag.org/content/129/33… A lot of work has been done but some of the fundamental questions have yet to be addressed: http://www.sciencemag.org/content/327/59…
11
@6 I could be wrong, but aren't O2 and N2 and other gases that aren't known to strongly react or otherwise interact with each other pretty uniformly spread according to altitude? How about CO2 or ozone or just about any other non-water atmospheric feature (barring some chemical that actively depletes them originating from an isolated source).
12
@11 - I did not watch the vid bcz I was on a mobile handset, and it's too painful to try to watch vids most of the time, so I was reacting to the text. Perhaps an error.
As to O2 and N2 being distributed uniformly, I have no idea. There is the issue of the 'ozone hole' over the antarctic, which suggests to me that ozone isn't distributed uniformly. Barring other concrete (ha!) information, given the dynamic nature of our atmosphere I would be hard-pressed to believe that anything at all is evenly distributed - in the Earth's atmosphere, or anywhere in the universe. But I'm willing to be wrong.
As to O2 and N2 being distributed uniformly, I have no idea. There is the issue of the 'ozone hole' over the antarctic, which suggests to me that ozone isn't distributed uniformly. Barring other concrete (ha!) information, given the dynamic nature of our atmosphere I would be hard-pressed to believe that anything at all is evenly distributed - in the Earth's atmosphere, or anywhere in the universe. But I'm willing to be wrong.
14
@5, @6
You didn't watch the lecture. The professor describes a series of well-designed physics experiments, not bioengineering or speculation.
He answers a question that you have not: why does liquid water suspended in the atmosphere form discrete clouds, rather than distribute in an even gradient corresponding to convection or thermodynamic variation?
It is not a stupid question, the answer suggested is surprising, and "clouds" do in fact exist, in addition to the tangentially related phenomenon of "clouding".
@6 - I saw a series of lenticular clouds in a line, blown off of Rainier and in progressive stages of dissipation, rather than a single lenticular cloud with a long tail. Might have been a different time of day, still pretty neato.
You didn't watch the lecture. The professor describes a series of well-designed physics experiments, not bioengineering or speculation.
He answers a question that you have not: why does liquid water suspended in the atmosphere form discrete clouds, rather than distribute in an even gradient corresponding to convection or thermodynamic variation?
It is not a stupid question, the answer suggested is surprising, and "clouds" do in fact exist, in addition to the tangentially related phenomenon of "clouding".
@6 - I saw a series of lenticular clouds in a line, blown off of Rainier and in progressive stages of dissipation, rather than a single lenticular cloud with a long tail. Might have been a different time of day, still pretty neato.
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