Sea echo in tropospheric ducting environments

Abstract

Path loss formulas for sea surface backscatter are developed for horizontally stratified tropospheric ducting environments. First‐order Bragg backscatter results coupled with ray and waveguide formalism serve as the basis for the development. Two features of composite model formalism, namely shadowing and tilting of the surface normal in the plane of incidence, are included in the development. Though developed for hh polarization, conventional composite model modifications for vertical polarization and depolarization can be incorporated into the echo models. Comparisons are made with previously generated parabolic equation results and with empirical model results generated by Engineers Refractive Effects Prediction System. These comparisons are for a frequency of 9.6 GHz for the standard atmosphere and for 14‐ and 28‐m evaporation ducts. Results apply to wind speeds of 10, 20, 30, and 40 knots (≈ 5, 10, 15, and 20 m/s).