A study of marine slicks damping effect on Doppler spectra of backscattered echoes from rough sea surfaces

ABSTRACT

Doppler spectrum of backscattered sea echoes from slick-covered sea surfaces is investigated in this paper, with emphasis on exploring the influence of marine sea slicks damping effect on Doppler spectral signatures including Doppler shift and spectral bandwidth. Model of local balance of wave energy inputs and outputs in wavenumber space is utilized for describing marine slicks damping effect, and the ‘choppy wave’ model is adopted for describing non-linear hydrodynamic interactions between ocean waves. The second-order small-slope approximation model combined with Monte Carlo technique is utilized for evaluating Doppler spectrum of backscattered field from clean or contaminated sea surfaces. Numerical simulations show that Doppler spectral bandwidths in slicks are reduced for almost all of the incidence angles ranging from $0^{{ }^{\circ }}$ to ${80}^{{ }^{\circ }}$, which is qualitatively consistent with wave-tank measurements. The Doppler shifts in slicks, however, can increase or decrease, depending strongly on incidence angle, which is also in qualitative agreement with measurements. The Doppler spectrum of radar sea echoes is promising in the detection marine slicks by virtue of radar Doppler signatures.

Disclosure Statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported in part by the National Natural Science Foundation of China [Grant No. 61701428], and in part by the Natural Science Basic Research Plan in Shaanxi Province of China [Grant Nos. 2019JQ-120].