Abstract Urban geometry and materials combine to create complex spatial, temporal and directional patterns of longwave infrared (LWIR) radiation. Effective anisotropy (or directional variability) of thermal radiance causes remote sensing (RS) derived urban surface temperatures to vary with RS view angles. Here a new and novel method to resolve effective thermal anisotropy processes from LWIR camera observations is demonstrated at the Comprehensive Outdoor Scale MOdel (COSMO) test site. Pixel-level differences of brightness temperatures reach 18.4 K within one hour of a 24-h study period. To understand this variability, the orientation and shadowing of surfaces is explored using the Discrete Anisotropic Radiative Transfer (DART) model and Blender three-dimensional (3D) rendering software. Observed pixels and the entire canopy surface are classified in terms of surface orientation and illumination. To assess the variability of exitant longwave radiation (MLW) from the 3D COSMO surface ( M LW 3 D ), the observations are prescribed based on class. The parameterisation is tested by simulating thermal images using a camera view model to determine camera perspectives of M LW 3 D fluxes. The mean brightness temperature differences per image (simulated and observed) are within 0.65 K throughout a 24-h period. Pixel-level comparisons are possible with the high spatial resolution of M LW 3 D and DART camera view simulations. At this spatial scale ( M LW 3 D . By simulating apparent brightness temperatures from multiple view directions, effective thermal anisotropy of M LW 3 D is shown to be up to 6.18 K. The developed methods can be extended to resolve some of the identified sources of sub-facet variability in realistic urban settings. The extension of DART to the interpretation of ground-based RS is shown to be promising.

中文翻译：

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一种基于地基热成像获取三维城市地表温度的新方法

摘要 城市几何和材料相结合，形成了长波红外 (LWIR) 辐射的复杂空间、时间和方向模式。热辐射的有效各向异性（或方向可变性）导致遥感 (RS) 得出的城市表面温度随 RS 视角而变化。在这里，综合室外尺度模型 (COSMO) 测试站点展示了一种从长波红外相机观测中解决有效热各向异性过程的新方法。在 24 小时研究期间的一小时内，亮度温度的像素级差异达到 18.4 K。为了理解这种可变性，我们使用离散各向异性辐射传递 (DART) 模型和 Blender 三维 (3D) 渲染软件来探索表面的方向和阴影。观察到的像素和整个冠层表面根据表面方向和照明进行分类。为了评估来自 3D COSMO 表面 (MLW 3 D) 的出射长波辐射 (MLW) 的可变性，根据类别规定了观测值。通过使用相机视图模型模拟热图像来测试参数化，以确定 M LW 3 D 通量的相机视角。每幅图像（模拟和观察）的平均亮度温差在 24 小时内都在 0.65 K 以内。M LW 3 D 和 DART 相机视图模拟的高空间分辨率可以进行像素级比较。在这个空间尺度 ( M LW 3 D 。通过从多个视角模拟表观亮度温度，M LW 3 D 的有效热各向异性显示为高达 6.18 K。开发的方法可以扩展到解决现实城市环境中某些已识别的子方面可变性来源。DART 扩展到地基 RS 的解释被证明是有希望的。