Measurements of optical attenuation through fog: Comparison between a 0.785 μm laser link and a visibility sensor

Joint measurements of optical attenuation have been carried out by a 0.785 μm laser link and by a visibility sensor with the aim of assessing if visibility can be used to predict path attenuation. Preliminary results drawn from the analysis of moderate radiation fogs in an urban area show that the time series of visibility and attenuation are well correlated when data are low-pass filtered (a simple moving average window with duration from 1-min to 5-min was applied). Moreover, the analysis evidences rather different and well defined statistical properties for the above slowly varying component and the fast signal fluctuations. If confirmed on a larger database, these features would represent an important step towards the development of a synthetic time series generator of fog events.