Assessment of SARAL/AltiKa Wave Height Measurements Relative to Buoy, Jason-2, and Cryosat-2 Data

Type Article
Date 2015-09
Language English
Author(s) Hito Sepulveda Hector1, Queffeulou Pierre2, Ardhuin FabriceORCID2, 3
Affiliation(s) 1 : Univ Concepcion, Dept Geophys, Concepcion, Chile.
2 : IFREMER, Lab Oceanog Spatiale, F-29280 Plouzane, France.
3 : CNRS Ifremer UBO IRD, UMR 6523, Lab Phys Oceans, Brest, France.
Source Marine Geodesy (0149-0419) (Taylor & Francis Inc), 2015-09 , Vol. 38 , N. Suppl.1 , P. 449-465
DOI 10.1080/01490419.2014.1000470
WOS© Times Cited 56
Note Special Issue: The SARAL/AltiKa Satellite Altimetry Mission
Keyword(s) Radar altimeter, significant wave height, satellite, SARAL, AltiKa, validation
Abstract SARAL/AltiKa GDR-T are analyzed to assess the quality of the significant wave height (SWH) measurements. SARAL along-track SWH plots reveal cases of erroneous data, more or less isolated, not detected by the quality flags. The anomalies are often correlated with strong attenuation of the Ka-band backscatter coefficient, sensitive to clouds and rain. A quality test based on the 1Hz standard deviation is proposed to detect such anomalies. From buoy comparison, it is shown that SARAL SWH is more accurate than Jason-2, particularly at low SWH, and globally does not require any correction. Results are better with open ocean than with coastal buoys. The scatter and the number of outliers are much larger for coastal buoys. SARAL is then compared with Jason-2 and Cryosat-2. The altimeter data are extracted from the global altimeter SWH Ifremer data base, including specific corrections to calibrate the various altimeters. The comparison confirms the high quality of SARAL SWH. The 1Hz standard deviation is much less than for Jason-2 and Cryosat-2, particularly at low SWH. Furthermore, results show that the corrections applied to Jason-2 and to Cryosat-2, in the data base, are efficient, improving the global agreement between the three altimeters.
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