optical air mass

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.

Related terms:

• air mass
• solar air mass
• warm air mass
• air-mass shower
• air-mass precipitation
• air-mass climatology
• air-mass analysis
• air-mass source region
• optical oceanography
• optical thickness