Of tropical cyclones and internal waves

A very astute meteorologist pointed me towards this awesome satellite image in the Indian Ocean.  Not only does it show tropical cyclone Anais heading towards Madagascar, but ZOMG the angle of the sun is just right to reveal a stunning train of internal waves.

Look at those lovely internal waves! Click the pic to see the original NASA image.

It may look like the waves are emanating from the hurricane itself, but they aren’t. These internal waves are generated by the tides. The cyclone is sitting right on top of Seychelles/Mascarene Plateau, a large flat bump in the deep Indian Ocean that generates internal waves as the tides slosh back and forth over it.  And this picture was taken at the perfect time.

It’s spring tide. These are some of the largest tides, so water is racing up and down and rip-roaring back and forth, causing some big-ass internal waves. These waves are so ridiculously large and have so much energy, that they change from regular internal waves into highly energetic internal waves known as solitons. Solitons are found all over the world and it’s actually pretty common to see them from space. In fact, there is a whole bunch of physical oceanographers that use satellite imagery such as this to find and track solitons.

But don’t think that the cyclone is getting left out of the internal wave making game.  It too is generating waves in its wake. But either they are too small to be seen or are obscured by clouds in this image.

I just think that we are very lucky to see these two very powerful phenomena together.

Superbig hattip to @sezick to tweeting me this photo.

Kim Martini (81 Posts)

Kim is a Physical Oceanographer at the Joint Institute for the Study of Atmosphere and Ocean at the University of Washington. She received her Ph.D. from the University of Washington in 2010. Her goal in life is to throw expensive s**t in the ocean. When not at sea, she uses observations from moored, satellite and land-based instruments to understand the pathways that wind and tidal energy take from large (internal tides) to small scales (turbulence).





3 comments on “Of tropical cyclones and internal waves
    • Because they are generated by the semidiurnal tide, the waves are generated every 12.42 hours. The image doesn’t indicate latitude and longitude, so I can’t give an exact size. Previous observations of solitons in that area by da Silva (http://www.sciencedirect.com/science/article/pii/S0967063710002426) indicate the crests are probably about 200-300 km wide. The crests that you see are actually very small, probably only about 1 m high.

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