Frequently Asked Questions
This Web page contains general questions from users about scatterometry data.
1. How do scatterometers work?
Radar scatterometers are satellite instruments designed to measure winds over the ocean from space. They can also be used for land and ice studies. A scatterometer transmits pulses of microwave energy and measures the returned echo. The energy in the echo depends on the electrical properties and roughness of the surface. Over the ocean, the surface roughness is a function of the near-surface vector wind, which generates ocean waves. With measurements made from multiple azimuth directions, the wind can be estimated from the radar measurements. Over land, the return echo is a function of the land cover.
2. Why use scatterometers for climate studies?
Radar scatterometers make frequent, very precise measurements of the globe. A variety of studies have shown that scatterometer measurements are very sensitive to key climate variables such as snowfall and melting in the polar regions and vegetation cover in the tropics, among others. A long time series of scatterometer data (dating intermittently back to 1978) has been collected. This long time series can thus be used to support climate change studies.
3. What is the advantage of active versus passive measurements?
Passive microwave data suffer from coarse spatial resolution and are sensitive to weather effects. Active microwave can ameliorate weather sensitivity and offers a new method for snow and ice research. Although active microwave data have similar spatial resolution as passive sensors (approximately 25 to 50 km), the enhanced-resolution imaging technique developed by Long, Hardin, and Whiting (1993) and Early and Long (2001) has expanded the utility of scatterometer data for polar studies.
Early, D.S., and D.G. Long. 2001. Image Reconstruction and Enhanced Resolution Imaging from Irregular Samples. IEEE Transactions on Geoscience and Remote Sensing 39(2): 291-302. (PDF, 325 KB)
Long, D.G., P.J. Hardin, and P.T. Whiting. 1993. Resolution Enhancement of Spaceborne Scatterometer Data. IEEE Transactions on Geosciences and Remote Sensing 32(3): 700-715.
The following citation describes a number of applications of scatterometers for climate studies:
Long, D.G., M.R. Drinkwater, B. Holt, S. Saatchi, and C. Bertoia. 2001. Global Ice and Land Climate Studies Using Scatterometer Image Data. EOS, Transaction of the American Geophysical Union 82(43): 503. Also available online at http://www.agu.org/eos_elec/010126e.html. Paper and electronic versions are available in a PDF file (3.9 MB).