Measurements of atmospheric turbidity from a network of sun-photometers in Italy during ALPEX

Three multiwavelength sun-photometers of new design and a Volz sun-photometer were operated during ALPEX SOP (March-April 1982) at three surface stations and at a mountain station in Italy. The turbidity measurements have been evaluated for the determination of aerosol particles optical thickness. A detailed study of this parameter, both in its daytime profile and in its variation during the whole ALPEX SOP period, was performed and the 'climatology' of the Angström parameters at each station was determined. The correlation with meteorological conditions during the measurement days and the days previous to measurements has confirmed the importance of precipitation scavenging and wet removal in restoring low values of parameter ? and high values of parameter ?. A computer program was written to plot the time pattern of aerosol optical thickness, which allowed in particular a comparison between the time patterns of this parameter at two stations horizontally close and at different elevations to be performed. In this way the optical characteristics of the interposed layer was investigated.