  Surface level hydrometeors, and specifically fog, cause attenuation of the
signal level measured by microwave communication networks. These networks
operate at frequencies of tens of GHz and form the data transport
infrastructure between cellular base stations. Thus, wireless communication
links are, effectively, an existing fog monitoring facility. Operational costs
are minimal, since the network is already deployed in the field, and
measurements are already stored by many of the cellular providers for quality
assurance purposes. This study shows the potential of microwave communication
networks for the detection of fog in challenging conditions where satellite
systems are often limited. In a first event, the ability to detect fog using
commercial microwave links, at a time when the satellite cannot detect the
phenomena due to high level cloud cover obscuring the ground level fog, is
demonstrated. The ability of the microwave system to rule out ground level fog
at times when the satellite detects a low-lying stratus cloud, but cannot
identify whether it is adjacent to the ground or at higher elevations above it,
is demonstrated in a second event. The results indicate the operative potential
of this technique to assist end users in reliable decision making that have
highly important economic and safety implications.
