Tag: clouds

Desktop Project Part 14: The cloud streets of southern Greenland

By Phil Plait | April 8, 2012 7:00 am

[The Desktop Project is my way of forcing myself to clean off my computer’s desktop by systematically writing a blog post for every cool picture I’ve been collecting and neglecting. I’ve been posting them every day for two weeks now. And there’s more to come!]

Regular readers know I’m fascinated by clouds. The shapes they take on and the processes that form them are really interesting, especially when more unusual and rare conditions produce spectacularly odd clouds.

You’ve probably never heard of "cloud streets", technically called horizontal convective rolls. I hadn’t either until recently, but they are amazingly cool-looking, especially when seen from space. Proof: check out this shot from March 2012 of cloud streets over Greenland taken by NASA’s Aqua satellite:

[Click to ennebulenate, or grab an even higher-res version.]

Isn’t that incredible? The formation mechanism for these clouds isn’t well understood, but it involves gently rising warm, moist air getting blown to the side by a shear wind. This starts up a rotation in the clouds and stretches them out into these fantastically long parallel strips. Each row you see is spinning along the long axis, and each one is spinning in the opposite direction of the one next to it (this diagram may help).

To give you a sense of scale, this image is over 2000 km (1200 miles) across! So these clouds can stretch a long, long way.

You probably see clouds every day, or certainly quite often. Yet there’s a lot we don’t know about them, and certainly many kinds I bet you’ve never even heard of. What else is there you might be missing that’s sitting in plain sight?

Image credit: Jeff Schmaltz/MODIS Land Rapid Response Team, NASA GSFC

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CATEGORIZED UNDER: Cool stuff, Pretty pictures

The long shadow of Mt. Rainier

By Phil Plait | October 26, 2011 12:49 pm

Here in Boulder we get magnificent sunsets, especially in the summer when the clouds interplay with the mountains to the west. But I have never seen anything like this: the shadow of Washington state’s Mt. Rainier cast along the clouds at sunrise:

Holy (yes, in this case appropriately) Haleakala! [Click to cascadenate.]

That’s amazing. Mt. Rainier is a volcano, climbing to a height of over 14,000 feet (4300 meters). There are no other mountains anywhere near that height nearby, so it’s really prominent in the landscape (by comparison, there are several fourteeners, as they’re called, in the Rockies, so they don’t stick out as much though they’re still breathtaking). The rising Sun catches the peak, and the shadow is cast on the underside of the cloud layer. The dramatic sunrise colors really make this an incredibly beautiful shot.

The KOMO news site has lots more pictures of this, too. Go take a look!

And remember, when you’re outside, it always pays to look around you for a moment. You never know what incredible vista nature may have in store for you.

Tip o’ the snow cap (har har) to John Baxter.

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CATEGORIZED UNDER: Cool stuff, Pretty pictures
MORE ABOUT: clouds, Mt. Rainier, shadow

Amazing video of a bizarre, twisting, dancing cloud

By Phil Plait | October 25, 2011 7:00 am

A couple of months ago, BAbloggee Henrik Magnus Ulriksen sent me a link to a video of a cloud that frankly left me — har har — twisting in the wind. When I saw it, I had the strong feeling it was authentic; taken with a hand-held camera, it doesn’t look obviously faked. But what it shows is very odd indeed.

The video is of a cumulonimbus cloud, a puffy white cauliflower-shaped cloud that forms when warm air rises rapidly. The camera view is between two buildings, and you can see the puffy cloud top just below the center of the frame. Keep your eye on the little wisp of cloud just above the cumulonimbus, right in the middle of the frame.

Did you see it? If it helps, the picture here shows you where to look. Starting at 9 seconds in, that little wisp suddenly snaps into a new shape, as if someone had stopped the video, waited for the cloud to change, then started up the video again. But it’s clear that’s not what’s going on; the video is smooth with no transitions.

Assuming the video is real, I had a sneaky suspicion it had to do with the electric currents generated inside the cloud, the same currents that create lightning. Clouds can carry huge electric potentials — essentially, the ability to move charges around — and that stored energy can be suddenly released, creating lightning. When that happens, the electric field resets itself, and starts to store up energy again.

But I had no clue how that would make the cloud appear to dance like that!

As it happens, by coincidence, I met Joel Gratz at the TEDxBoulder talk in September. Joel is a meteorologist who runs websites like Open Snow and Colorado Powder Forecast. I sent him the video, and sure enough a short while later he had a reply for me.

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No, a new study does not show cosmic-rays are connected to global warming

By Phil Plait | August 31, 2011 9:32 am

The way some of the media report on climate change can be simply stunning. For example, an opinion piece in The Financial Post has the headline "New, convincing evidence indicates global warming is caused by cosmic rays and the sun — not humans".

There’s only one problem: that’s completely wrong. In reality the study shows nothing of the sort. The evidence, as far as the limitations of the experiment go (that’s important, see below), do not show any effect of cosmic rays on global warming, and say nothing at all about the effect humans are having on the environment.

What did you do, Ray?

OK, first things first: why should we even think cosmic rays might affect climate? There are several steps to this, but it’s not too hard to explain.

We know that clouds form by water molecules accumulating on seed particles, called condensation nuclei. The physical processes are complex, but these particles (also called aerosols) are suspended in the air and water droplets form around them. The more of them available, the better water can condense and form clouds (although of course this also depends on a lot of other things, like how much water is in the air, the temperature, the height above the ground, and so on).

Cosmic rays, it turns out, may play a role in this too. They are subatomic particles that zip through space at high speed. We are bombarded by them all the time, in fact! They hit atoms and molecules in the Earth’s atmosphere, depositing their energy there. This affects aerosol formation rate, and therefore might affect cloud formation. Clouds are bright and white, and reflect sunlight. Therefore they affect global warming.

So the whole idea goes like this: the more cosmic rays there are, the more aerosols are made, the more easily clouds can form, the more sunlight gets reflected back into space, and the less global warming we get. It’s controversial, for sure (Discover Magazine interviewed a proponent of this idea in 2007) but worth looking into.

ConCERNing clouds

In practice, the actual connection between cosmic rays and cloud formation is really hard to determine. So a group of scientists at the European particle lab CERN decided to test the basics. They created a cloud chamber, bombarded it with cosmic rays, and examined the results. They found two very interesting things:

1) The number of aerosols created went up vastly as the particles blasted the chamber. That would seem to indicate that cosmic rays really are tied to global warming. Except…

2) The actual total number of aerosols created was way below what’s needed to account for cloud formation. Sure, there were more aerosols, but not nearly enough.

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Lovely, frigid ripples

By Phil Plait | February 20, 2011 7:00 am

The weather here in Boulder has been pretty warm lately, and most of the snow is gone. I know that this can change at any moment (and in fact we’re due for more snow in a day or so), and NASA has provided a chilling but ethereally lovely reminder that this winter has been one to remember:

This image was taken by the Terra satellite on January 24, and shows what happens when there is a confluence of three conditions. The first is extremely frigid arctic air blowing down from the north west. The second is warmer waters in the Atlantic; the air above the water gets humid and rises into the colder air, condensing to form clouds. But the third is what’s needed to make this amazing rippling effect: a layer of warm air above the cold layer, called a temperature inversion. This acts like a ceiling for the rising, condensing air below. The clouds that form can’t rise any higher, so they roll east with the moving air, forming these "streets".

I think the effect of this image is heightened by the lack of clouds over land; it’s the ocean water that creates the clouds, so the skies were clear over the Atlantic seaboard, allowing us to see the snow-covered landscape. I like to think of how much meteorologists and climate scientists can learn from images like this, and of course that’s why we launch satellites like Terra into orbit. But I also don’t have too much of a problem just sitting back and admiring the beauty and artistry of our planet from space, either.

Image credit: NASA, Jeff Schmaltz, MODIS Rapid Response Team, Goddard Space Flight Center. Addition credit to my old pal Michael Carlowicz.

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CATEGORIZED UNDER: Cool stuff, Pretty pictures
MORE ABOUT: clouds, Terra

The cloudy, warming Earth

By Phil Plait | June 11, 2010 7:07 am

NASA just released an interesting picture of our home planet, taken from the GOES satellite:


[Click to massively englobenate.]

This image is in the infrared, and maps out the heat emitted from Earth. Brighter spots are giving off more IR — like the desert region in southwest South America, and the westernmost tip of Africa peaking over on the right — and darker spots show areas where less IR is emitted.

You might think that these dark spots are cooler, but you have to be careful here. The dark areas are actually cool high clouds. But they also trap the heat of the Earth — they don’t heat up themselves, but prevent the heat below them from escaping. High clouds like this are in reality warming us up slightly, even though they themselves are cold!

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CATEGORIZED UNDER: Antiscience, NASA, Pretty pictures

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