A model of Linke's turbidity factor, T(L), is developed by means of up
dated spectral extraterrestrial irradiances and extinction coefficient
s of gaseous absorbers. It is shown that the new values of T(L) are cl
early different from those obtained by Kasten's formula which paramete
rizes the optical thickness of the clean dry atmosphere. The model is
used to investigate the dependence of T(L) on the relative optical air
mass and to elucidate the relationships linking T(L) to Angstrom's tu
rbidity coefficient and to the water vapor content. For any T(L), the
corresponding value related to the air mass 2.0 can be determined. Suc
h a standardized value is independent of solar elevation and is theref
ore strictly representative of the atmospheric turbidity. It can be li
nked to Angstrom's turbidity coefficient. Practical procedures and alg
orithms for computing the standard Linke's turbidity factor and determ
ining Angstrom's turbidity coefficient are described. A relationship f
or converting the T(L) values obtained by Kasten's formula into the ne
w values is proposed.