Phenomena

Measuring Wind Speed by Satellite

Weather modeling and forecasting in recent decades have benefited enormously from the availability of more data. For example, satellites now measure wind speeds over the open ocean, instead of data simply coming from isolated ships and buoys.  The satellites do this by measuring the roughness of the ocean using radar or GPS signals bounced off the ocean surface. From this researchers can construct a map of wave height and direction like the one in the animation above. For a large body of water, waves are primarily generated by wind shearing the water at the interface. The waves we see are a result of the Kelvin-Helmholtz instability between the wind and ocean. Because this is a well-known behavior, it is possible to connect the waves we observe with the wind conditions that must have generated them. (Image credit: ESA; animation credit: Wired; submitted by jshoer)

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