Integrating nephelometer performance in fog and thick Haze

Summary In fogs and thick hazes integrating-nephelometer measurements are affected by the angular truncation error due to the integration of the atmospheric scattering function on a truncated angular range. A method of experimental investigation on the actual consequences of this error is exposed. Equations that take into account both truncation error and photometric systematic errors are proposed and validated through a field comparison by nephelometer and transparency measurements. It is shown that the integrating nephelometer can substitute the transmissometer in all visibility conditions if photometric errors are avoided. Paper presented at the 1° Congresso del Gruppo Nazionale per la Fisica dell'Atmosfera e dell'Oceano, June 19–22, 1984, Rome.