Ground-based far-infrared emissivity measurements with the University of Wisconsin absolute radiance interferometer (ARI)

The infrared Absolute Radiance Interferometer (ARI) instrument - developed at University of Wisconsin-Madison, Space Science and Engineering Center (SSEC) - measures absolute spectrally resolved infrared radiance (200-2000 cm-1 or 5-50 μm at 0.5 cm-1 resolution) with ultra-high accuracy (< 0.1 K 3-sigma brightness temperature at scene temperature). The ARI prototype instrument was deployed for field measurements of clear-sky far infrared (FIR) surface emissivity and radiances on the SSEC rooftop. Currently there are very few measurements available in the FIR spectral region. Our targeted samples include snow and ice surfaces which are important for radiative cooling in the polar regions. We will demonstrate the ARI instrument configuration, capability for ground-based measurements in the FIR region, and the retrieval of infrared emissivity spectra. The ARI ground-based FIR measurements would support scientific applications that involve FIR studies, such as the PREFIRE (Polar Radiant Energy in the Far InfraRed Experiment) and the European FORUM (Far-infrared-outgoing Radiation Understating and Monitoring) missions.