Trends in Attenuation Coefficients in Athens, Greece, from 1954 to 1991

Abstract

Unsworth and Monteith's attenuation coefficient TUM was calculated from midday cloudless sky data in Athens, Greece, for the period 1954 to 1991. An interdependence between TUM and the Linke factor TL was found and is expressed as a mathematical function. It was also shown that the minimum turbidity levels occur during the winter and maximum levels occur during summer. An analysis of the long-term variation of the attenuation coefficients depicts the deterioration of air quality during the same period. The dependence of the ratio of diffuse to global radiation on the attenuation coefficient TUM, is also presented.