ESTIMATION OF THE LINKE AND UNSWORTH-MONTEITH TURBIDITY FACTORS IN THE VISIBLE SPECTRUM - APPLICATION FOR ATHENS, GREECE

Expressions for the Linke, T-Lvis, and Unsworth-Monteith, T-Uvis, turb idity parameters in the visible region of the solar spectrum are deriv ed. They are based on new determinations of the visible transmittances for the various atmospheric constituents obtained by spectrally integ rating the wavelength-dependent atmospheric transmittances. Applicatio n of the T-Lvis and T-Uvis expressions for Athens is made for the firs t time; this is done from measurements of direct solar irradiance in t he period 1992-1995. A linear interdependence between T-Lvis and T-Uvi s is derived, as in the case of their broadband counterparts. The seas onal, monthly and daily variations of these turbidity parameters are a lso investigated. (C) 1997 Elsevier Science Ltd.