Collaborative Research: Longwave Radiation Processes on the Antarctic Plateau

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*** 9807501 Walden This project is an experimental study of long-wave radiation processes near the surface at South Pole station. Instrumentation capable of high resolution measurements of the infrared radiation fluxes at the snow surface -- a so-called Fourier Transform Interferometer -- will be developed and put in place in late 1999 and operated through the following austral winter. Supporting observations of the temperature and moisture profiles in the lower atmosphere, and of ice crystals in the atmospheric boundary layer will be made. Long-wave radiation (also called infrared or thermal radiation) is an important component in the energy balance of the atmosphere. On the antarctic continent radiation processes dominate the surface energy budget. In summer the balance is made up of four terms (incoming and reflected short-wave or solar radiation, and emitted and reflected long-wave radiation); in winter after sunset the short-wave terms are zero. The emitted long-wave radiation varies with temperature so that the condition of radiation balance at the surface will determine a particular value of the surface temperature. This study includes several experiments concerning the emission characteristics of snow, of ice crystals in the atmosphere, and of greenhouse gases near the surface. The concurrent environmental conditions such as cloud base altitude, temperature and humidity structure, ice crystal sizes and concentrations will allow the development of a climatology of cloud properties, and substantially improved representations of radiation processes in general circulation models. ***