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

Comments (12)

  1. Wow, Phil, awesome foto. I love those striations in the cloud layer.

    And speaking of cool fotos laying around on your desktop, when are you going to get around to doing a post on those MRO dust devil images? Haven’t seen any of those here yet…

  2. I wonder if there are some cloud cars too, it would be a shame if all those streets were left to waste.

    While we’re at this topic, I’ve been looking for a book about clouds for quite some time now (I’m talking about science books, of course). Any good recommendations?

  3. Very cool Phil. Now if only we could get some images as seen from the surface of the Earth to go with this, narrow in comparison as they may be.

  4. Thomas

    I believe the term cloud ‘street’ comes from the world of soaring sailplanes and hang gliders. To us, those rows of clouds are indicators of soarable lift that allow long distance flight. Follow the street and you can stay up, cross the street into the clear area between them and you likely find sinking air.

  5. Cool image. And I love the “Desktop Project” idea… so many images either get forgotten about or else deserve another look every now and then! Just ‘cuz somethings not brandy-new doesn’t mean it’s not totally awesome.

  6. Have you heard of the Cloud Appreciation Society? That was great day for me, when I discovered their existence. I immediately became a proud, card-carrying member.

  7. kat wagner

    Thanks for posting the link to the diagram too; I was wracking my poor brain trying to figure out how the streets roll. And roll they do, like big long rolls of paper, pulling their neighbors in the opposition direction. Cool!

  8. VinceRN

    Wow. In my (totally unqualified) opinion this is the winner, so far, of your desk top project pictures. Never knew such a thing existed. The world sure is a cool place.

  9. Apropos of nothing, the raw data from Rosetta’s 2010 flyby of the asteroid Lutetia has been now released.

    A series of NAC images were assembled into this flyby movie:

  10. Those vortexes looks very similar to those created by the big volcano on Jan Mayen.
    They are a problem for the local airtraffic at takeoff. The vortex creates very sudden 180 degree shift in wind direction.

    The streets lasts longer at Greenland, because of normally much calmer weather conditions.

  11. HP

    I’ve looked at clouds from both sides now.

  12. Brian Too

    I’ve often seen something at sunset and wondered about it.

    It seems like these “cloud streets” tend to form as the sun is going down. Yet I’m aware that the setting sun could simply be lighting the clouds in a way that suggests a regular pattern when there really isn’t one.

    Am I seeing something real, or not? Full disclosure, I’m talking about a continental climate, not coastal and not marine.


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