Sensitivity of modeled far-IR radiation budgets in polar continents to treatments of snow surface and ice cloud radiative properties

While most general circulation models (GCMs) assume spectrally independent surface emissivity and non-scattering clouds in their longwave radiation schemes, spectral variation of the index of refraction of ice indicates that, in the far-IR, snow surface emissivity can vary considerably and ice clouds can cause non-negligible scattering. These effects are more important for high-elevation polar continents where the dry and cold atmosphere is not opaque in the far-IR. We carry out sensitivity studies to show that in a winter month over the vast region of Antarctic Plateau, including snow surface spectral emissivity and ice cloud scattering in radiative transfer calculation can reduce the surface net downward far-IR flux and net atmospheric far-IR emission. The magnitude of these changes averaged over a winter month and over the entire Antractic Plateau are still ~1Wm^-2 or even larger. This study substantiates the needs to further study far-IR radiative processes and properties as well as to improve their representations in the GCMs.