In Situ Measurements of Ice and Snow Emissivity in the Far‐Infrared

Abstract This paper describes the first field deployment of the Far INfrarEd Spectrometer for Surface Emissivity far‐infrared Fourier transform spectrometer to an Arctic environment and shows retrievals of the emissivity of ice and snow in the wavenumber range 400–1,200 cm −1 at viewing angles of 35° and 50°. The retrieved ice emissivity shows a variation of 0.05 between the peak value at around 950 cm −1 and the minimum value at around 750 cm −1 . The emissivity is also between 0.01 and 0.02 lower for the higher viewing angle. The emissivity of snow is higher and shows less variation with both viewing angle and wavenumber but it is 0.01 less than one below 900 cm −1 . This has implications for remote sensing and climate modeling in this wavenumber range as it implies that both the spectral and angular variation of emissivity must be taken into account. The retrieved ice emissivity agrees well with the emissivity modeled using Fresnel equations. The retrieved snow emissivity agrees well with modeled snow emissivity but further independent measurements of the snow physical properties are needed to test the performance of the model in the far infrared.