Comparison of significant wave heights derived from the ERS-1, TOPEX, GEOSAT and SEASAT altimeters and retrieved from ERS-1 SAR wave mode spectra

A comparison of significant wave heights Hs was performed using satellite altimeter data available between 1978 to 1994 from SEASAT, GEOSAT, ERS-1 and TOPEX. The purpose was to estimate the degree of accuracy between the different instruments. Statistical properties of H s as obtained from the altimeters are found to be compatible with those from in situ measurements in the North Atlantic. All H s data sets are fitted to appropriate distribution functions. Furthermore, an assessment and validation of H5 retrieved from ERS-1 SAR Wave Mode (SWM) data with spatially and temporally collocated altimeter data from ERS-1 and TOPEX during 1994 is given. The values of SWM-retrieved monthly mean H s are generally higher than those of the ERS-1 altimeter and lower than those of the TOPEX altimeter. The SWM-retrieved H s agree better with TOPEX altimeter data, than with the ERS-1 altimeter data. Regional comparison are performed and an attempt is made to investigate the differing behaviour of pure windsea and swell.