Atmospheric turbidity is shown to have a major influence on direct luminous efficacy. Based on this observation a physical direct luminous efficacy model is derived from spectrally integrated turbidity equations. Two independent data banks are used to validate this model in comparison to state of the art direct luminous efficacy models found in the literature. Atmospheric turbidity is estimated from horizontal visibility measurements.
arXiv: Astrophysics::Solar and Stellar AstrophysicsPhysics::Medical PhysicsAstrophysics::Cosmology and Extragalactic AstrophysicsPhysics::Optics