High spectral resolution clear sky atmospheric radiation case studies over the Arctic are presented. Measurements from the ground based Extended Range Atmospheric Emitted Radiance Interferometer (ER-AERI) systems at the SHEBA and North Slope of Alaska (NSA) Barrow sites and from the high altitude ER-2 based High Resolution Interferometer Sounder (HIS) during FIRE ACE are compared to line-by-line calculations of up- and down-welling longwave radiance. Specific topics include the determination of new air-broadened water vapor continuum coefficients in the 380 to 590 wavenumber region and their implication on atmospheric fluxes, up- and down-welling comparisons in the 1400 to 1800 wavenumber region and their implcations to remote sensing of upper tropospheric water vapor, and observations of longwave emissivities of sea ice and open water.