Two-Dimensional Spectra of Radar Returns from Sea: 1. Theoretical and Numerical Study of the Group Line

Florestan Platzer (1) , Marc Saillard (2) , Vincent Fabbro (1)

1 DEMR, ONERA, Université de Toulouse [Toulouse]
2 UTLN UFR ScT - Université de Toulon - UFR Sciences et Techniques

The work presented here aims at interpreting the pattern observed at low frequencies in wavenumber-frequency (k,) representations (dispersion diagrams) of radar returns from sea surface. This pattern is sometimes referred to as the "group line" in the literature and is supposed to result from the nonlinear behavior of the signal with respect to surface profile. To confirm this assumption, we have calculated the patterns generated by various nonlinear terms of second order in sea surface height. It is shown that the resolution in frequency of most data is not sufficient to allow for an accurate representation of the group line through an FFT. A methodology is proposed to define an average slope of the group line, which can be interpreted in terms of velocity.

Mots clés: LOW-GRAZING-ANGLE; RADAR REMOTE SENSING; DISPERSION SPECTRUM; SEA SURFACE ELECTROMAGNETIC SCATTERING

Domaines: Océan, Atmosphère

Florestan Platzer, Marc Saillard, Vincent Fabbro. Two-Dimensional Spectra of Radar Returns from Sea: 1. Theoretical and Numerical Study of the Group Line. Journal of Geophysical Research. Oceans, 2019, ⟨10.1029/2019JC015121⟩. ⟨hal-02493149⟩