A parametric model for ocean wave period from Ku band altimeter data

Abstract

Using a large collocated data set of altimeter and buoy measurements, we examine the relationship between the altimeter Ku‐band measurements of significant wave height, Hs, backscatter coefficient, σ0, and the buoy wave period. This is used to derive an empirical altimeter wave period model for TOPEX, Poseidon, Jason‐1, ERS‐2, Envisat, and GEOSAT follow‐on. We show that there is a step change in the response of σ0 at around 13 dB and above this value σ0 is not related to wave period. The results are compared to algorithms proposed by two previous authors (Gommenginger et al., 2003; Quilfen et al., 2004) and examined in terms of absolute accuracy (RMS error), ability to replicate the joint distribution of wave height and period, and residual trends with various parameters. The new algorithm is shown to perform better than the previous algorithms in all metrics considered. Finally, we demonstrate that there is a limiting accuracy achievable for a function of the form f(Hs, σ0) and that our model comes close to this.