Linke Turbidity Factor
A measure of atmospheric turbidity, equal to the ratio of total optical depth to the Rayleigh optical depth.
It is an important parameter in solar radiation studies.
It is a function of wavelength.
θ = Linke's turbidity factor 
I0 = flux density of the solar beam just outside the earth's atmosphere [Wm-2]
I = flux density measured at the earth's surface with the sun at a zenith distance which implies an optical air mass m [Wm-2]
Im,w = intensity which would be observed at the earth's surface for a pure atmosphere containing one centimetre of perceptible water viewed through the given optical air mass [Wm-2]
F. Linke, "Transmissions-Koeffizient und Trübungsfaktor", Beitr. Phys. fr. Atmos. 10, 91-103 (1922)
See also: Turbidity.