Longwave Radiation Processes over the Antarctic Plateau

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The atmosphere over the Antarctic Plateau plays a unique role in the global climate system. It is the coldest and driest atmosphere on earth, and radiation processes dominate both the surface and the top-of-atmosphere energy budgets. In summer, the four radiation components (downward and upward, shortwave and longwave) are each in the range of 100 to 400 watts per square meter, generally exceeding the sensible and latent heat fluxes by at least an order of magnitude. In winter, there is no shortwave radiation, so the downward and upward longwave fluxes are the dominant contributors to the surface energy budget. When spectrally resolved, longwave radiation is also useful for remote sensing of atmospheric and surface properties. Thus it is desirable to develop methods for remote sensing by polar-orbiting satellites so that the entire continent can be characterized. Surface-based observations are invaluable for validating satellite observations, as well as for obtaining information about climatic processes that are best studied in situ. Five separate projects will be based upon analysis of data from South Pole Atmospheric Radiation and Cloud Lidar Experiment (SPARCLE), a full-year experiment of the effects of clouds, water vapor, atmospheric ice crystals, and surface snow, on the longwave radiation spectrum measured at the surface. Project 1 will use the climatological database of longwave spectra to determine the contributions of different gases to the downward longwave flux at the surface and the surface cloud radiative forcing. Project 2 involves longwave radiative properties of Antarctic clouds and their effects on the surface and atmospheric energy budgets. Project 3 involves the measurement of humidity profiles and development of retrieval algorithms of boundary-layer temperature and humidity profiles for Antarctica. Project 4 involves the simultaneous retrieval of the surface temperature and the spectral emissivity of snow. Project 5 is a study of near-surface atmospheric temperature profiles. The experimental data and the subsequent analysis products are expected to generate research in other areas, including remote sensing, climate modeling, and weather forecasting in Antarctica for potential year-round logistical operations. The data analysis projects proposed here will also provide data from the Antarctic Plateau useful in constraining and testing general circulation models.***