Parameter Tree:
EARTH SCIENCE > ATMOSPHERE > ATMOSPHERIC RADIATION > OPTICAL DEPTH/THICKNESS

Definition:
In radiative transfer, optical thickness or optical depth is the mass of
a given absorbing or emitting material in a vertical column of
unit cross-sectional area and extending between two specified
levels. 


Reference:
WMO. 1966. International Meteorological Vocabulary. WMO/OMM/BMO, No. 182. TP.
91., Switzerland.