Issues concerning atmospheric turbidity indices

Knowledge of atmospheric turbidity coefficients is very important in meteorology, climatology, atmospheric pollution monitoring, and in the prediction of solar energy availability under cloudless skies. This paper provides a thorough review on a number of atmospheric turbidity indices and on the several methods that have been developed in the past few decades. The Lambert–Bouguer–Beer law is the basic relationship underlying the derivation of various turbidity indices. Turbidity can be referred to as monochromatic (narrow band) wavelengths, broadband wavelengths, and the total spectrum. Narrow band turbidity is measured using sun photometers, while the other two turbidities are measured using pyrheliometers with broadband pass filters. The Ångström's turbidity coefficients and the Linke's turbidity factor are among the most frequently used atmospheric turbidity coefficients.