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ENVISAT RA-2 IMAR products JASON-1 IGDR TOPEX IGDR GEOSAT Follow-On IGDR

Cross-validation of ENVISAT RA-2 SWH and SIGMA0 P.Queffeulou IFREMER DRO-DOP-LOS preliminary results. ENVISAT RA-2 IMAR products JASON-1 IGDR TOPEX IGDR GEOSAT Follow-On IGDR October 4 to November 13, 2002 Selection of ground-track crossing points within 1 hour time window

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ENVISAT RA-2 IMAR products JASON-1 IGDR TOPEX IGDR GEOSAT Follow-On IGDR

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  1. Cross-validation of ENVISAT RA-2 SWH and SIGMA0 P.Queffeulou IFREMER DRO-DOP-LOSpreliminary results • ENVISAT RA-2 IMAR products • JASON-1 IGDR • TOPEX IGDR • GEOSAT Follow-On IGDR • October 4 to November 13, 2002 • Selection of ground-track crossing points within 1 hour time window • Comparison of 1-second measurements and/or 100 km along-track averages

  2. Flags • JASON igdr qual_1hz_alt 1hz_num_val >= 18 off_nadir_angle_wvform < 0.1deg^2 land & ice flags • TOPEX igdr alt_bad1: backscatter and swh bits land & ice flags • GFO igdr qual_1hz_data: bit 0 (land) bit 4 6 7 9 10 19 20 21 1hz_num_val = 10 • ENVISAT imar quality indicator measurement confidence data bits 0 to 17 ocean_flag 1hz_swh_num_val >= 19 off_nadir_angle_wvform < 0.1deg^2

  3. Ku SWH 1-second colocated data

  4. Discussion of SWH results Our cross-validation results JASON TOPEX GFO Reg. 0.9553 SWH - 0.00217 1.0111 SWH - 0.0399 0.9894 SWH - 0.2198 Mean dif. 0.15 0.00 0.25 Std 0.34 0.26 0.21 N 255 227 93

  5. Status of JASON TOPEX GFO SWH validation (using buoy and / or cross-satellite validation, proposed corrections) JASON TOPEX GFO (D.Cotton) 1.0472 SWH - 0.0137 1.0520 SWH - 0.0674 1.0633 SWH + 0.0808 (P.Queffeulou) 1.0581 SWH - 0.0405 1.0461 SWH - 0.0541 1.0268 SWH + 0.1064

  6. Results for ENVISAT Ku SWH (applying above corrections) JASON TOPEX GFO 1.0004 SWH - 0.0364 1.0637 SWH - 0.1094 1.0520 SWH - 0.1529 1.0108 SWH - 0.0635 1.0577 SWH - 0.0958 1.0159 SWH -0.1193Actual D.Cotton study / buoy: SWH env = 0.9453 SWH buoy + 0.1359 ie a ‘correction’ to Envisat SWH of: 1.0579 SWH - 0.1438 use of a larger data set to confirm this correction and to estimate errors on the coefficients

  7. Ku backscatter coefficient 1-second colocated data

  8. Discussion of Sigma0 results Our cross-validation results JASON TOPEX GFO Mean (ENV.- X) -2.9728 -2.9376 -3.0338 Std 0.301 0.256 0.1861 N 246 217 93 Status of JASON TOPEX GFO sigma0 validation JASON is adjusted on TOPEX Long term global averages: TOPEX – GFO = 0.31 dB (4/12/2000…) TOPEX – ERS-2 = 0.84 dB (22/6/2001…) GFO – ERS-2 = 0.51 dB (22/6/2001…)

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