Validation of ENVISAT RA-2 and JASON-1 altimeter wind and wave measurements

Collocation procedures and analysis developed at LOS-CERSAT are applied to validate ENVISAT RA-2 and JASON-1 SWH, sigma0 and wind speed measurements, using buoy, ERS-2, TOPEX and GEOSAT FO altimeter data. Preliminary results are presented. ENVISAT and JASON Ku SWH are shown to be in close agreement with buoy data. Nevertheless comparisons with GFO, TOPEX or ERS-2 indicate that both altimeters underestimate high SWH. For sigma0, in the past, because of the lack of absolute calibration, the practice was to calibrate sigma0 in order to get similar wind speeds when using an operational algorithm. Present Ku sigma0 comparisons show: 0.12 dB and 0.05 dB biases of ENVISAT relative to GFO and TOPEX, respectively; 0.69 dB and 0.59 dB biases of JASON relative to GFO and ERS-2 respectively. For wind speed, negative biases and large scatter are observed from the comparisons of ENVISAT and JASON with buoy measurements.