Environment

Ocean Comet

ImaGeo iconImaGeoBy Tom YulsmanMar 13, 2013 5:33 PM

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In this image captured by the MODIS instrument on NASA's Aqua satellite on March 8, winds rushing over and around Heard Island in the Southern Ocean north of Antarctica create v-shaped waves in the atmosphere that trail off for hundreds of miles. (Image: NASA EOSDIS Worldview) It may look something like a comet, but what you're looking at in the image above is a trail of disturbance left behind tiny Heard Island in the "Furious Fifties" of the Southern Ocean. There's very little in the way of landmasses to disrupt the winds between 40 °S and 60 °S latitude, north of Antarctica. So they blow nearly constantly in a globe-girdling band. As those winds rush over and around Heard Island, they create waves in the atmosphere, resulting in the chevron shaped "cloud streets" behind it. The winds also cause clouds to pile up on the west side of the island (to the left). And as they rush over the high terrain, the air descends on the east side, inhibiting cloud formation. This has punched a hole in the cloud deck behind Heard Island. In October, the VIIRS instrument on another NASA satellite, Suomi NPP, captured this beautiful image of the island: 

The VIIRS instrument on the Suomi NPP satellite captured this image of Heard Island on October, 27, 2012. (Image: Suomi NPP VIIRS Imagery and Visualization Team Blog — http://rammb.cira.colostate.edu/projects/npp/blog/) Check out the blog of the VIIRS visualization team for more information. But the long and short of it is that the"tail" behind the island is once again caused by disturbance to the airflow.(And make sure to click on this image — and all of them, for that matter — to check out the fine details.) I'll leave you with this image, courtesy of NASA's awesome Earth Observatory, of an entire swam of ocean comets:

V-shaped waves fan out from the South Sandwich Islands in the southern Atlantic Ocean. The image was captured on Nov. 23, 2009 by the MODIS instrument on NASA's Terra satellite. (Image: NASA Earth Observatory.)

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