Mini Contest: What Is This?

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October 28, 2008

We are giving away a free SPOT t-shirt to the first person who can tell us about what is going on in this image.

Let us know in the comments…

Wow.  Great responses everyone.  While this wasn’t any trick question, most of you did get it correct.  Click on to see the answer and the winner…

The image is of “ship-wave-shaped” clouds or Kelvin waves in the Southern Indian Ocean from the NASA MODIS Image of the Day for yesterday, October 28, 2008.

They are called this because they resemble ship waves (or “Kelvin ship waves”), which are the V-shaped wakes left by moving objects, such as ships or even ducks.

In this case, the cloud patterns were caused by the Prince Edward Islands in the South Indian Ocean (not to be confused with the Prince Edward Island in Canada). As the wind flows past the islands, it is swept around and over it leaving a wake similar to that of a ship– hence the name “ship-wave-shaped” clouds. The pattern is not accidental or coincidental, there is a physical reason for it. Wind behaves like a fluid; when it encounters an obstacle, it must move around it, leaving behind a wake (like Von Karmann vortices), or a visible wave pattern. Ship-wave-shaped cloud patterns form as the air alternately cools and warms on the wave peaks and troughs, causing clouds to form on the peaks, but not the troughs.


And the winner is…

Ryan Owens

Ryan if you could email us at [email protected] we will get you that t-shirt.

Thanks again everyone for your interest and participation.


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