# 17-21-106

luminous extinction coefficient, <of the atmosphere>

av

measure that expresses the attenuation of the direct illuminance when the Sun's rays cross vertically the pure and dry atmosphere (Rayleigh atmosphere)

where m is the relative optical air mass weighted to take account of the relative spectral transmittance characteristics of the atmosphere

Note 1 to entry: The luminous extinction coefficient has unit one.

Note 2 to entry: This entry was numbered 17-737 in CIE S 017:2011.

Publication date: 2020-12