Impact of Evaporation Duct on Line-of-sight Propagation of Electromagnetic Waves

Generated by the evaporation of seawater, evaporation duct (ED) is an air-sea interaction that occurs over the sea surface. The electromagnetic (EM) waves will be trapped in ED when propagating beyond line-of-sight. However, the impact of ED on line-of-sight propagation is rarely reported. The path loss (PL) oscillates within the first few kilometers when the EM wave propagating in line-of-sight and then greatly reduced. Simulation results shown that the PL in ED layer can be reduced by more than 40 dB on line-of-sight propagation. The experiment PL selected from the South China Sea in March 2022 is 28.2 dB lower than the simulation PL in standard atmosphere, which verifies the conclusions. The conclusions contribute to the design and use of marine radar and communication systems.