Sky imager for the analysis of the optical influence of thin homogeneous clouds

我们与加拿大环境部合作，管理和科学地管理来自加拿大范围的太阳光度计网络(Aerocan)的QA数据。地面太阳光度测量已成为评估基于卫星的气溶胶遥感算法的标准工具，也是气溶胶模型性能的关键指标。尽管有观点认为太阳光度测量代表着交钥匙地面真理，但仪器和环境问题值得关注。其中最关键的是薄均匀云(THC)对气溶胶光学厚度(AOD)估计的影响。最广泛使用的云筛选算法受到其在高频光学变化方面对云的算法定义的限制。与THC事件相关的AOD通常绕过这一标准。他说，目前正在研究一种基于光谱和时间的云筛选形式的混合方法。这项技术仅在使用THC的独立指示剂的情况下进行了有限的测试。在接下来的几年里，我们将把重点放在布拉特湖的校准场地、埃格伯特的相对浑浊的场地和我们当地的舍布鲁克场地的三氯甲烷问题上。后一个地点受到清澈到中度混浊的混合气氛的影响，并且经常受到三氯甲烷的影响。此外，还可以使用用于获取天空图像的自动化系统来生成THC的空间指标。我们的经验是，天空图像为THC的存在提供了上下文支持。舍布鲁克是Aerocan研究云筛查程序的关键地点，因为它是申请者的家(而且从视觉经验中我们知道，THC在这个地点经常发生)。天空成像仪位于调查人员及其HQP所在的位置，这一点很重要，因为我们已经认识到，为了支持自动化测量，人工观察是必要的，而且频繁的视觉观察是研究生参与和培训的重要组成部分。因此，需要为总的天空成像仪提供经费，以补充舍布鲁克的Aerocan太阳光度计。

We manage and scientifically QA data from a Canada-wide network of sunphotometers (AEROCAN) in collaboration with Environment Canada. Ground based sunphotometry has become a standard tool for evaluating satellite based aerosol remote sensing algorithms and a key indicator of aerosol model performance.  In spite of the viewpoint that sunphotometry represents turn-key ground-truth there are instrumental and environmental issues which merit attention. One of the most critical is the impact of thin homogeneous clouds (THCs) on estimates of aerosol optical depth (AOD). The most widely used cloud screening algorithm is limited by its algorithmic definition of clouds in terms of high frequency optical variations. AODs associated with THC events often bypass this criterion.      A hybrid methodology for a spectrally and temporally based form of cloud screening is currently being investigated. This technique has only been tested in a limited fashion using independent indicators of THC. In the next few years we will focus on the issue of THCs at the calibration site of Bratt's Lake, the relatively turbid site at Egbert and our local site at Sherbrooke. This latter site is influenced by a mixture of clear to moderately turbid atmospheres and is often affected by THCs.      Automated systems for the acquisition of sky images can be employed to yield spatially based indicators of THC. Our experience has been that sky images give a contextual support for THC presence. Sherbrooke is a key AEROCAN site for the study of cloud screening procedures since it is the home site of the applicants (and because we know from visual experience that THCs are a frequent occurrence at this site). That the sky imager be located where the investigators and their HQPs are located is important since we have come to realize that human observations are necessary to support automated measurements and that frequent visual observations are an essential component in graduate student involvement and training. Funding is accordingly requested for a total sky imager to complement the AEROCAN sunphotometer at Sherbrooke.