Forward Radar Propagation Over a Rough Sea Surface: A Numerical Assessment of the Miller-Brown Approximation Using a Horizontally Polarized 3-GHz Line Source

Forward Radar Propagation Over Oil Slicks on Sea Surfaces Using the Ament Model With Shadowing Effect

“…Indeed, it takes the surface roughness into account by multiplying the Fresnel reflection coefficient of a plane surface by the term exp(−2R 2 a ) (for Gaussian statistics, with R a the Rayleigh parameter). Nevertheless, as shown in the literature [9], this simple model enables fast results which are consistent with rigorous methods for R a 1.25 (R a = k 1 σ h cos θ i , with σ h the surface RMS height, k 1 the incident wave number, and θ i the incidence angle). The model was then improved in [8] by taking the shadowing effect into account.…”

“…In conclusion, the forward radar propagation over rough surfaces using the Ament model [9] has been extended to the case of rough layers, and applied to a sea covered in oil, by taking the shadowing effect into account. A comparison between a clean sea surface and a sea covered in oil has been detailed.…”

“…For a wind speed u 10 = 10 m/s, the RMS height of the clean sea surface is σ sea h 0.659 m, and the ones for the contaminated sea are σ hA = σ hB 0.616 m. As well, the RMS slope of the clean sea surface is σ sea s 0.186, and the ones for the contaminated sea are σ sA = σ sB 0.116. Then, for x 2 = 2 km, h 2 ranges from 0 to 30 m, which implies that R a,r ranges from 0.310 to 0.931, which is in the validity domain of the Ament model [9]. Likewise, for x 2 = 5 km, h 2 ranges from 0 to 80 m, which implies that R a,r ranges from 0.124 to 0.786.…”

“…10 with respect to the height of the receiver h 2 , and is compared between a clean sea surface and a sea covered in oil, for f = 3 GHz and u 10 = 7 m/s: on the left, x 2 = 2 km, and on the right, x 2 = 5 km. For x 2 = 2 km, h 2 ranges from 0 to 30 m, which implies that the reflection Rayleigh parameter R a,r ranges from 0.151 to 0.453, which is in the validity domain of the Ament model (R a,r < 1.25 [9]). Likewise, for x 2 = 5 km, h 2 ranges from 0 to 80 m, which implies that R a,r ranges from 0.060 to 0.382.…”

“…Let us note that following [4][5][6], the results of the approximate methods are in excellent agreement with exact numerical methods. Indeed, the Ament model is valid for R a,r < 1.25 [9], and here, for x 2 = 2 km, h 2 ∈ [0; 180] m, which implies that R a,r ∈ [0.031; 0.402], and for x 2 = 5 km, h 2 ∈ [0; 450] m, which implies that R a,r ∈ [0.012; 0.383]. The numerical results for H polarization highlight a higher contrast between the sea and the oil for this frequency, in comparison with Fig.…”