Spectral emissivity from field observations of natural and artificial surfaces

The spectral emissivity of frozen surfaces in polar regions is among the spectral features of the far-infrared contribution to the Earth radiation budget that FORUM aims to observe. This paper describes the activities undertaken to retrieve the spectral emissivity from measurements carried out in the field. We will outline the experimental setup to measure the radiation emitted by surface samples using the Far-Infrared Radiation Mobile Observation System (FIRMOS), a Fourier transform spectroradiometer measuring in the 100-1000 cm-1 spectral range. Particularly, we will focus on the results of our retrieval of the spectral emissivity of ice and snow samples collected and measured at the top of Mount Zugspitze (Germany, 2962 m a.m.s.l.). Knowledge of the emissivity of a material is also of interest for many technological applications.Therefore, we will show how FIRMOS observations will be employed to investigate the spectral properties of Passive Radiative Cooling materials that are engineered to exhibit a negligible absorption at solar wavelengths and to dissipate heat to outer space through the atmospheric transparency window.