ERS-1 scatterometer measurements - Part II: An algorithm for ocean-surface wind retrieval including light winds

An algorithm for retrieving European Remote Sensing Satellite (ERS-1) scatterometer winds, denoted the Rufenach-Bates-Tosini (RBT) algorithm, is developed and used to retrieve winds collocated within +/-25 km of buoy measurements in two oceanic regions, equatorial and midlatitude, An improvement in the retrieved RBT winds over the European Space Agency (ESA) winds is due mainly to a geophysical model employing the full available wind-speed range, including the lightest winds, This model, denoted BMOD5, is tuned by using the scatterometer and buoy measurements, resulting in two different models for the midlatitude and equatorial regions, The RBT retrieved winds exhibit 1) a larger number of solutions (wind vectors) and 2) smaller biases in wind speed than the ESA wind product, The increase in the number of retrieved winds is primarily due to lighter winds employed, 0.2 m/s to 18 m/s; whereas, the ESA winds are truncated near 3 m/s, The ESA winds underestimate the highest winds significantly, by about 20%, and overestimate the lightest winds, The RBT wind bias is less than a few percent at the highest winds and a few tenths of a m/s at the lowest winds, Both algorithms retrieve 180 degrees ambiguous directions almost as often as the true direction, Regression fits to the minds using the RBT algorithm produce standard deviations of 1 m/s and 25 degrees near the equator for winds varying from 0.2-10 m/s and 1.2 m/s and 25 degrees at midlatitudes for winds varying from 0.2-18 m/s, provided that the ambiguities are removed.