Spatial analysis of the electromagnetic bias in radar altimetry

Measurements of the electromagnetic bias have shown that bias increases with wind speed until about 11 m/s and then begins to decrease. Two possible causes are investigated. First, it could be due to a shift in the backscatter power modulation to the forward or rear face of the wave crests. Second, it could be due to the backscatter power becoming more homogenous throughout the wave profile. These two possibilities are tested using data collected from an oil platform in the Gulf of Mexico during a six-month period in 1990. This study is novel because it uses knowledge of the spatial distribution of both the backscatter and wave displacement for the study of the electromagnetic bias. Both causes outlined above contribute to the bias decrease, but the second cause seems to be the dominant effect. This study is in support of the upcoming mission of the NASA/CNES Jason-1 altimeter