A laboratory investigation on electromagnetic bias in sea level measurements by microwave altimeters
Résumé
To contribute to a better understanding of the Electromagnetic Bias in radar altimetry, a serie of experiments was conducted in the I.M.S.T. large windwave facility using a focused beam radar set at 13.5 GHz frequency. For pure wind wave fields we found the bias to be a quadratic function of each of the commonly used prurameters, namely the significant wave height, the wind speed, the water elevation skewness and significant slope. The bias divided by the significant waveheight is a linear function of these parameters. The coefficients in bias representation as a function of either the significant waveheight or the wind speed are significantly different from values obtained in field experiments. This led us to conclude that none of the latter parameters can be taken solely to account for all observed bias variations. Instead, dimensionless parameters such as the wave skewness or a dimensionless waveheight are shown to be more appropriate. They include more or less explicitely the state of development of the wind wave field of interest.
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