Radio-wave propagation above the sea surface: Investigation of the subrafraction cases

Summary form only given. At cm and mm wavelengths, the propagation of radio waves above the sea surface is strongly affected by the refraction mechanism. Within the Marine Surface Boundary Layer (i.e. the first tens of meters) and for grazing angles, the presence of an evaporation duct plays a major role by modifying the radar coverage diagrams, comparatively to the standard atmosphere cases. Even if an evaporation duct is generally present in the maritime environments, situations with no ducts may also occur. Such situations are referred as subrefraction cases for which the radio-electrical horizon is reduced.