CoAuthors

Hui Feng (Univ. of New Hampshire, United States); Bertrand Chapron (IFREMER, France); Yves Quilfen (IFREMER, France); Fabrice Ardhuin (IFREMER, France)

It is common knowledge that ocean microwave radiometer measurements of brightness temperature are sensitive to sea foam produced as waves break with increasing wind speed. But this phenomenon coexists with thermal emission variations due to a changing surface geometry and overlying atmosphere, the former also closely linked to changes in wind waves. Thus empirical or simple additive models remain the primary approaches to estimate some measure of whitecap surface coverage (percentage) as well as foam thickness or active vs. passive breaker information from ocean radiometer surface emissivity measurements. A recent example is the use of WindSat off-nadir radiometer data at 10 and 37 GHz to produce an empirical measure of these parameters. This project has similar objectives but will make use of coincident multi-frequency radar and radiometer data onboard the Jason platforms. The clearest potential advantage for this near nadir combination comes in the very different impact of geometry and foam on these passive and active sensors for the same surface during wave breaking onset and development; this for moderate to high wind speeds of 7-20 m/s. Analyses will make use of metoc buoy measurements and global wave model (WAVEWATCH 3) data to provide underlying measures wind as well as the degree of expected wave steepness and breaking.