Longwave Radiation Processes on the Antarctic Plateau

南极高原的大气在全球气候系统中起着独特的作用。它是地球上最冷和最干燥的大气，辐射过程支配着地表和大气顶部的能量收支。在夏季，四个辐射分量（向下和向上，短波和长波）各在100至400瓦/平方米的范围内，一般超过感热通量和潜热通量至少一个数量级。冬季没有短波辐射，因此向下和向上的长波通量是地表能量收支的主要贡献者。在光谱分解后，长波辐射也可用于遥感大气和地表特性。因此，需要发展利用极轨卫星进行遥感的方法，以便能够描绘整个大陆的特征。基于地面的观测对于验证卫星观测以及获取关于气候过程的信息是非常宝贵的，而这些信息最好在现场进行研究。五个独立的项目将基于南极大气辐射和云激光雷达实验（SPARCLE）的数据分析。SPARCLE是一项为期一年的实验，研究云、水蒸气、大气冰晶和地表雪对地表测量的长波辐射光谱的影响。项目1将利用长波谱气候学数据库确定不同气体对地表向下长波通量和地表云辐射强迫的贡献。项目2涉及南极云的长波辐射特性及其对地表和大气能量收支的影响。项目3涉及测量南极洲的湿度廓线和发展边界层温度和湿度廓线的检索算法。项目4涉及同时反演地表温度和雪的光谱发射率。项目5是对近地表大气温度剖面的研究。预计实验数据和随后的分析产品将在其他领域产生研究成果，包括南极洲的遥感、气候模拟和天气预报，以供可能的全年后勤业务使用。这里提出的数据分析项目还将提供南极高原的数据，这些数据对约束和测试一般环流模型很有用

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.***