http://www.esa.int/esaEO/SEMJFHWX7YG_index_0.html
The SMOS sensor works in the ‘L-band’, at frequencies around 1.4 GHz, which also allows surface wind speeds over oceans to be derived, even in cloudy and rainy conditions.
When winds reach gale force over oceans, breaking waves and whitecaps affect the microwave radiation being emitted from the surface. This means that when a storm builds, changes in the emitted radiation can be linked directly to the strength of the wind over the sea.
In addition, the radiation detected by SMOS is far less disturbed by rain and atmospheric effects than higher microwave frequencies.
Since clouds and rain are typical of tropical cyclones, measurements from SMOS uniquely complement observations made in extreme conditions, when measurements from other satellites become less accurate.
This means that SMOS has the potential to improve accuracy for forecasting the strength of tropical cyclones.
SMOS’s new-found capability was demonstrated by analysing SMOS data over Hurricane Igor, which reached category 5 in the North Atlantic in 2010.
The large swath and frequent revisits allowed the satellite to pass over the hurricane nine times during 11–19 September.
Surface wind speeds were estimated from SMOS brightness temperature images using a technique developed by scientists from the French Research Institute for Exploration of the Sea, Ifremer, and Collect Localisation Satellites, CLS, through ESA’s Earth Observation Support to Science Element programme.
The animation at the top shows the result of their work. The estimates of surface-wind speed agree with hurricane model forecasts and data taken over the hurricane by NOAA aircraft.
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