Since we are using ASCAT scatterometer data in the lesson, we will introduce it here. But we won’t go into much depth since it is covered in the prerequisite COMET lesson mentioned earlier (Using Scatterometer Wind and Altimeter Wave Estimates in Marine Forecasting).
ASCAT wind data comes from active radar instruments called scatterometers that emit and receive microwave radiation. The radiation is not affected by clouds, which is why scatterometers can scan the surface in almost all weather conditions - clear, cloudy, or rainy. The data is also useful because it’s available in data-sparse oceanic regions where extreme weather events, such as extratropical cyclones, are generated.
The ASCAT scatterometer flies on EUMETSAT’s MetOp satellites. ASCAT has six antennas that allow for simultaneous coverage of two 550-km wide swaths separated by a 670-km gap. You’ll notice the gap when viewing the data - it’s where little useful wind information is reflected back to the instrument.
Scatterometers are used to monitor a range of parameters - from sea ice and snow cover, to land surface parameters, such as soil moisture and vegetation. However, their primary use is to measure wind speed and direction over the ocean surface (10 m above) for use in weather analysis and forecasting.