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SYFY WIRE Bad Astronomy

An Island Makes Waves in the Sky

By Phil Plait

I don’t know why cool cloud patterns seen from space fascinate me so; maybe it’s just my inherent love of science, clouds, space, nature, and art.

Actually, after writing that sentence, maybe I do know why.

Also, sharing that love is fun, too. So for you, here is a really nice shot of a wave cloud pattern seen by Landsat8:

What you’re seeing are called “ship wave clouds,” because the overall pattern resembles the waves of water as a ship moves through the ocean. The cause of this is Île Amsterdam, an incredibly remote and tiny volcanic island located in the southern Indian Ocean. It’s only about 10 kilometers across, and the peak reaches to about 850 meters above sea level. You can just see the edge of the island on the left-hand side of the image, peeking through the hole in the clouds.

As a steady wind blows over the volcano, it rises up and cools. Moisture in the air condenses, forming clouds. But as the air cools it sinks, warms up, and the water evaporates again, so the clouds disappear. The warm air rises, and boom! Repeating pattern. At the same time, the wind gets pushed around the volcano as well, so the pattern gets wider downstream.

This photo is one of the best I’ve ever seen of the phenomenon … though when it happens over an island chain it’s pretty amazing as well. I see similar things sometimes as the wind blows over the Rocky Mountains, just a few kilometers to the west of my home. When wind, water, and geology interact, it’s a canvas on which nature paints nearly infinite varieties of beauty.

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