What's At The Edge Of A Cloud? Scientists soared through clouds with a new instrument that takes 3-D pictures of the edge. What they learned about the size and density of droplets surprised them and might lead to better forecasts.
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What's At The Edge Of A Cloud?

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What's At The Edge Of A Cloud?

What's At The Edge Of A Cloud?

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ARI SHAPIRO, HOST:

If you go on Instagram and search for the hashtag #clouds, the results is more than 44 million posts. People love good cloud formations, especially scientists. They're fascinated by the inner workings of even the most mundane clouds. NPR's Nell Greenfieldboyce tells us about one team that has just made a cloud breakthrough.

NELL GREENFIELDBOYCE, BYLINE: A life studying clouds is not what you would have predicted for Raymond Shaw. He remembers being a Cub Scout and trying to get the weather badge.

RAYMOND SHAW: And we had to memorize the types of clouds, and I really hated it. I actually didn't like all these Latin - you know cumulus, stratocumulus - all of these special names for clouds.

GREENFIELDBOYCE: But later he got interested in snowflakes, which, of course, come from clouds. And he ended up working at Michigan Technological University where he studies clouds secrets. Lately, he's been looking at the most boring clouds you can imagine.

SHAW: If you ask a child to draw a cloud, they would draw a little, white, puffy cloud floating in the air all by itself, and that's the kind of cloud we were looking at.

GREENFIELDBOYCE: What he wants to understand, at a very fine level of detail, is how the cloud interacts with the surrounding air. So Shaw's team recently flew through clouds in an airplane equipped with a new instrument.

SHAW: The instrument creates a small, three-dimensional picture of everything that's inside of a volume.

GREENFIELDBOYCE: The volume isn't a big amount of space. It's like a cigar-sized section of the cloud, but it's big enough to be revealing.

SHAW: So we can not only see how many droplets there are and how big they are. We can also see how they're distributed in space.

GREENFIELDBOYCE: What they focused on were the cloud's edges where dry air is mixing in. You might think all the droplets at the edge of a cloud would evaporate a little bit - that they would all shrink. But that's not what happens. Shaw says dry air seems to creep in and evaporate some droplets completely. Others survive in wispy cloud filaments surrounded by clear air.

SHAW: The droplets that are remaining are just as big as the droplets that are in the center, kind of the protected core of the cloud were no evaporation has taken place. That was a surprise to us.

GREENFIELDBOYCE: They report on their work in the journal Science. Shaw says getting this kind of intimate look at clouds is just neat.

SHAW: But the amazing thing is that it really does have consequences. Those little details in the cloud eventually form a link in a chain that leads to a weather forecast or an understanding of how climate will change.

GREENFIELDBOYCE: The findings amazed Marcia Baker. She's a retired cloud physicist from the University of Washington in Seattle. Back in the 1980s, she and a colleague first proposed that this is how dry air would mix with a cloud.

MARCIA BAKER: This new instrument seems like a real tour de force. It's quite astonishing we were able to make measurements down to this level, and it's, of course, very gratifying.

GREENFIELDBOYCE: She says other kinds of clouds might behave differently, like colder clouds with ice crystals. And Shaw says he's really interested in understanding those clouds, too. Nell Greenfieldboyce, NPR News.

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