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Up In the Clouds


March Meeting madness is going strong here in Portland. Once again, if you're in the area tomorrow, the public lecture by James Kakalios on the Physics of Superheroes promises to be great.

On the meeting side, the number of talks this year is mind boggling (8000!). Through watching a handful of them so far I have come to two definite conclusions. Number 1: People are still using math. Liberally. Number 2. Physicists love to model stuff. Seriously, those folks will model just about anything. It's like catnip to them (in this analogy, physicists are cats).

One example is work done by Yong Wang of UCLS, modeling how fair weather clouds get their cauliflower like shape. (Wang and collaborator Giovanni Zocchi just had their paper accepted to PRL).

It's been known for a while that these fair weather clouds are formed when droplets of moisture hanging out up in the sky, are pushed up by thermal plumes coming from the ground. Those plumes tend to have nice little dome-like tops that put those cute little round bumps on the clouds.

What is new here is that although people generally knew that the clouds were formed this way, no one had modeled the system because cloud systems are very complex. So when it comes to physicist catnip, Wang and Zocchi make their catnip resemble very complex catnip in nature...ok that metaphor is falling apart. From the authors:

"What’s important about this work is that it describes (quantitatively) one specific aspect (the shape) of a complex system (the cloud) in terms of the coherent structures in the system (the thermal plumes). Usually one cannot do this with complex non-linear systems. In this case, this
procedure gives a simple description of a complex everyday phenomenon."

I did not know, going into the session, that fair weather clouds were formed this way. I also learned that although the plumes give clouds that cauliflower shape on top, you might notice that fair weather clouds tend to be flat on the bottom. You would assume that the plumes would make the clouds cauliflower-shaped all around. Well, they do. But it turns out that the flat appearance of clouds is created right at the point where the temperature gets high enough that the droplets evaporate. It's interesting that it can create such a distinct line.

When asked what this modeling could be good for, the researcher replied, "Video games." He suggested the models be used to create more realistic clouds in virtual worlds. The reporters wanted to know if there were climate or weather modeling applications, but Wang said no. No one asks a cat what else catnip is good for, but I hope other researchers can at least learn from Wang's modeling techniques and get something more out of this research.

(Photo courtesy of Michael Jastremski.)

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