Longwave radiation on snow-covered mountainous surfaces

Longwave radiation in snow-covered alpine environments was investigated based on LOWTRAN7 calculations, The irradiance from the sky and from the surrounding topography were determined separately in order to detect the influence of the topography on longwave radiation balance. Sensitivity studies showed that the irradiance from the surrounding terrain is determined primarily by the atmospheric conditions within the investigated area and by the surface temperature of the surrounding terrain. In snow-covered environments, the air temperature is usually above the snow surface temperature and the effects of the air between the topography and the receiving surface may be relevant. Longwave irradiance from the surrounding terrain is an important component of the energy balance at the snow surface on inclined slopes and should be considered for areal investigations. A simple parameterization that accounts for the effects of the air is proposed for efficient calculation of longwave irradiance from snow-covered topography.