Sea breeze signatures on line‐of‐sight microwave links in tropical coastal areas

The unusual fast fading observed around middays on line‐of‐sight microwave links in a tropical coastal area is described. Fading was as deep as 20–30 dB with fade rates double the normal rates. The fading is attributed to multipath propagation produced under sea breeze circulations. Sea breeze circulations modify the boundary layer and cause the formation of a low level super‐refractive layer associated with a temperature inversion above the ground. At the same time, an elevated layer of high refractivity variance is formed at the boundary of the cool and humid marine air flowing on‐shore and the relatively dry and hot air flowing offshore. However, when there is a strong vertical heat transfer from the ground, a modified convective boundary layer with a height of about 100–150 m above the ground with a capping elevated layer at the upper boundary of the sea breeze front is formed. In both cases, specular reflections and scattering of radio signals from the layered structures, along with multiple refractive paths are expected to be the cause of the observed fast daytime fading, which is conspicuously absent on inland paths.