The determination of infrared emissivities of terrestrial surfaces

Abstract

Infrared signals received in the 8- to 12- window by weather satellites and air- craft are dependent on surface temperature (T,), surface emissivity (e), and atmospheric interference. It seems that nowhere can variations of e be neglected in order to evaluate T, data correctly. Methods of determining e of typical surface materials are presented. They are: (1) determinations from reflection data obtained from polished rock samples run on a spectro- photometer; (2) a fieldworthy device constructed by the authors, called the emissivity box; and (3) e as inferred from Tiros data. Over the Sahara, emissivity of SiO2-containing surfaces is frequently below 0.95. Emissivity of water and oil on water are shown to differ.