atmosphere_optical_thickness_due_to_frozen_water_in_cloud 1 [XXXX] "Cloud" means the component of extinction owing to the presence of frozen water particles. The optical thickness is the integral along the path of radiation of a volume scattering/absorption/attenuation coefficient. The radiative flux is reduced by a factor exp(-"optical_thickness") on traversing the path. A coordinate variable of radiation_wavelength or radiation_frequency can be specified to indicate that the optical thickness applies at specific wavelengths or frequencies. The specification of a physical process by the phrase "due_to_" process means that the quantity named is a single term in a sum of terms which together compose the general quantity named by omitting the phrase. The phrase "frozen_water" means ice.