Optical Air Mass

optical air mass

[′äp·tə·kəl ′er ‚mas]
A measure of the length of the path through the atmosphere to sea level traversed by light rays from a celestial body, expressed as a multiple of the path length for a light source at the zenith.

Optical Air Mass


the ratio between the air mass penetrated by sun rays for a given zenith distance of the sun and the air mass that would be penetrated by the rays if the sun were at the zenith. The air mass is assumed to extend from the upper boundary of the atmosphere to the surface of the earth. The concept of optical air mass is used in meteorology in calculating the attenuation of solar radiation in the atmosphere.


Kurs meteorologii (Fizika atmosfery). Edited by P. N. Tverskoi. Leningrad, 1951.