A Comparative Study of Rough Sea Surface and Evaporation Duct Models on Radio Wave Propagation

Microwave and millimeter-wave propagations near the sea surface are greatly affected by the vertical atmospheric refractivity profile and the sea surface. To accurately simulate or predict the performance of ship radar systems, the evaporation duct model and rough sea surface models are usually incorporated into the parabolic equation to model electromagnetic wave propagation. The Paulus–Jeske (PJ) model and Naval Postgraduate School (NPS) model are the most widely used to make the vertical atmospheric refractivity profile, and the roughness sea surface is modeled with the effective reflection coefficient of the rough surface or the generation of the rough sea surface. There are four widely used rough sea surface approximations called Ament, Miller–Brown, shadowed, and hybrid for rough sea surface modeling. In this study, numerical simulation is first used to compare the different rough sea surface modeling methods. Then, evaporation duct measurement data and C-band propagation experimental data are used to compare the evaporation duct models and the four rough sea surface models that are combined with evaporation duct models for propagation loss prediction. The simulation results show that the shadowing of radio waves by the rough sea surface and sea surface structure are important factors affecting the transmission of radio waves in evaporation ducts, and the difference in the path loss predicted by different rough sea surface approximations may exceed 10 dB at the same location. In particular, the frequency and wind speed will increase. In addition, the experimental data show that the evaporation duct can be better diagnosed using different evaporation duct models at different atmospheric stabilities. When the air–sea temperature difference is positive, the PJ evaporation duct is recommended; otherwise, the NPS model is better, and the results of the shadowed and hybrid rough sea surface models are in better agreement with the observations.