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

我们与加拿大环境部合作，管理和科学地来自加拿大范围内的太阳光度计网络（AEROCAN）的QA数据。地面太阳光度计已成为评估卫星气溶胶遥感算法的标准工具和气溶胶模型性能的关键指标。尽管人们认为太阳光度法代表了关键的地面事实，但仪器和环境问题值得注意。其中最关键的是薄均质云（THCs）对气溶胶光学深度（AOD）估计的影响。使用最广泛的云筛选算法受到其基于高频光学变化的云的算法定义的限制。与四氢大麻酚事件相关的aod通常绕过这一标准。目前正在研究一种以光谱和时间为基础的云筛查形式的混合方法。该技术仅以有限的方式使用四氢大麻酚的独立指标进行了测试。在接下来的几年里，我们将重点关注布拉特湖校准地点、埃格伯特相对浑浊的地点和我们在舍布鲁克的当地地点的THCs问题。后一地点受清澈至中度浑浊大气混合物的影响，并经常受到四氢大麻酚的影响。用于获取天空图像的自动化系统可用于产生基于空间的THC指标。我们的经验是，天空图像为THC的存在提供了背景支持。Sherbrooke是AEROCAN研究云筛选程序的关键站点，因为它是申请人的所在地（因为我们从视觉经验中得知，thc在该站点经常发生）。天空成像仪位于研究者和他们的hqp所在的地方是很重要的，因为我们已经意识到人类观测是支持自动测量的必要条件，而频繁的视觉观测是研究生参与和培训的重要组成部分。因此，要求为全天空成像仪提供资金，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.