Statistical Analysis of Hybrid Atmospheric Ducts over the Northern South China Sea and Their Influence on Over-the-Horizon Electromagnetic Wave Propagation

Atmospheric ducts are special super-refractive atmospheric structures that can cause over-the-horizon propagation of electromagnetic waves. Different types of atmospheric ducts have different influences on electromagnetic wave propagation. Owing to the complex marine atmospheric environment, different types of atmospheric ducts often occur together. When evaluating the performance of an electromagnetic system near the sea surface, the combined influence of various atmospheric ducts should be considered comprehensively. In this paper, the statistical distribution of atmospheric ducts over the northern South China Sea is analyzed using sounding data and reanalysis data. This paper uses the parabolic equation model to analyze the propagation characteristics of microwaves near the sea surface in the presence of both surface and evaporation ducts. It is found that compared with cases where only one type of atmospheric duct is considered, a hybrid atmospheric duct structure can capture more microwave energy at a lower receiving height. At an antenna height of 5 m, the path loss begins to fluctuate beyond a propagation distance of 50 km, with the maximum fluctuation reaching about 15 dB. Microwave propagation characteristics at different microwave frequencies and antenna heights are also simulated and analyzed.