Angular distribution of clear sky short wavelength radiance

Over 3000 scans of the clear sky short wavelength (0.3–3.0 μm) radiance were used to produce sky radiance contour maps for solar zenith angles 32° to 80°. The radiance contours are symmetrical about the solar meridian with minimum radiance in the solar meridian at approximately 90° to 110° from the sun. There is no significant change in contour for a change in aerosol optical depth from 0.1 to 0.5. The clear sky radiance is given analytically by N(ψ) = (1.63 + 53.7e−5.49ψ + 2.04 cos² ψ cos θ^*) (1 − e^{−1.90 sec θ}) (1 − e^{−0.53 sec θ}*) where θ^* is the solar zenith angle, θ the zenith angle of the sky radiance direction, and Ψ is the scattering angle between sky and sun directions.