# Airlight formula

From Glossary of Meteorology

## airlight formula

(

*Also called*Koschmieder's law.) A version of the radiative transfer equation that predicts the luminance due to airlight (*L*_{a}) in the direction of a perfectly black object near the horizon.*L*

_{a}can be used to calculate daytime visual range. For horizon sky luminance

*L*

_{h}, horizontally uniform extinction coefficient σ, and distance

*x*from the observer: