Observations of the emissivity of snow and ice surfaces from the SAAMEX and MACSI airborne campaigns

This paper presents results from an airborne campaign over snow and ice (SAAMEX). Observations of millimetre wavelength channel sensitivity to snow depth, wetness and vegetation cover have been collected using an airborne microwave radiometer (MARSS). Snow was found to substantially reduce the emissivity of dry snow at 157 GHz, although this effect was lost as the snow wetness increased. The sensitivity to snow was smaller at 89 GHz than at 157 GHz. Vegetation was found to mask the appearance of underlying snow if the snow was dry. For wet snow there was little difference between forest and open spaces. The sea ice experienced pressure ridging against the coastline: the observed brightness temperature was higher and more variable when viewing parallel to the ridges than when viewing perpendicular, if the ridges were snow covered. Bare ridges showed no azimuthal dependence.