ArticleAngular distribution of overcast sky short wavelength radiance

A detailed analysis of 1438 all-sky scans of shortwave radiance (95 skypoints per scan) for overcast skies shows that angular dependence of the (suitably normalized) diffuse sky radiance can be represented by the analytical expression. NC2(ψ)= 0.45 + 1.12θ∗ + 0.43 cos θ + 0.72 exp[−1.88ψ] where Cosψ = Cos θ∗cos θ + sin θ∗cos φ θ = sky zenith angle, Φ = sky azimuth angle (relative to the sun), θ∗ = solar zenith angle. Both θ∗ and ψ are in radians.