Unified model of radiance patterns under arbitrary sky conditions
Unified model of radiance patterns under arbitrary sky conditions
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DOI：
10.1016/j.solener.2015.02.019
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发表时间：
2015-05
期刊：
影响因子：
6.7
通讯作者：
M. Kocifaj
中科院分区：
文献类型：
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作者：
M. Kocifaj
在照明工程应用中，迫切需要模拟更逼真的天空的辐射/亮度模式，以模拟室外和室内空间的日光可用性。毫无疑问，天空亮度/亮度的角度行为是决定不同朝向和窗户大小房间日光条件的关键因素。因此，目前人们正在努力寻找一种通用的、可扩展的、能接受实际气象情况的日光模型。自然天空的辐射量既不是单调的，也不是天顶/方位角的光滑函数，主要是由于存在破碎的云阵或散布在整个天顶上的单一云层。在这篇文章中，我们展示了我们如何解决这些现象，并为浑浊、多云的大气开发了一个通用的天空辐射模型。该模型考虑了更高的散射级、气溶胶光学、表面反照率和单云的统计相关贡献。地面的辐射度取决于云场的整体特征，如光谱光学厚度、光谱反射率、高度、天空位置、大小和形状。结果表明，当云层遮挡太阳直射光束时，单次散射近似不能再现太阳周围区域的辐射。单次散射的概念也高估了个别云的反射。在计算模型中加入二次散射通常会使云层边缘的辐射模式变得平滑和不那么陡峭，这在自然界中是常见的。数值演示基于UniSky模拟器(Kocifaj和Fecko，2014)，该模拟器允许对各种云配置进行建模，并可供公众使用。
The radiance/luminance patterns that simulate more realistic skies are urgently needed in lighting engineering applications to model daylight availability in exterior and interior spaces. Undoubtedly, the angular behavior of sky radiance/luminance is a key factor determining the daylight conditions in rooms with variable orientations and window sizes. Therefore, much effort is currently expended in search of a universal, scalable daylight model that accepts actual meteorological situations.The natural sky radiances are neither monotonic nor smooth functions of zenith/azimuth angle, primarily due to the presence of broken cloud arrays or single clouds scattered over the whole sky vault. In this paper we show how we have addressed the phenomena and developed a universal sky radiance model for a turbid, cloudy atmosphere. This model accommodates higher scattering orders, aerosol optics, surface albedo, and the statistically relevant contributions of single clouds. The radiance at ground depends on the bulk characteristics of cloud fields, such as spectral optical thickness, spectral reflectance, altitude, positions on the sky, sizes, and shapes. We have shown that single scattering approximation fails to reproduce the radiance in the circumsolar region when clouds block the direct solar beams. The single scattering concept also overestimates reflection by individual clouds. Incorporation of double scattering into a computational model generally makes the radiance patterns smooth and less steep at the edges of clouds as commonly occur in nature. The numerical demonstrations are based on UniSky Simulator (Kocifaj and Fecko, 2014) which allows for modeling of various cloud configurations and is available for public use.