Remote estimation of complete urban surface temperature using only directional radiometric temperatures

Publication date: 1 May 2018
Source:Building and Environment, Volume 135
Author(s): Lu Jiang, Wenfeng Zhan, James Voogt, Limin Zhao, Lun Gao, Fan Huang, Zhe Cai, Weimin Ju
Complete urban surface temperature ( T c ) is a key variable for quantifying the urban surface - atmosphere interactions. The estimation of T c usually requires detailed knowledge of surface geometry and facet temperatures, which are difficult to obtain by remote sensing. Therefore, simple but efficient strategies for the remote estimation of T c are currently lacking. Facing this challenge, we proposed a comprehensive solution to estimate T c remotely using only the directional radiometric temperatures (DRTs) without the assistance of ground-based information. By comparing T c with the nadir temperature (T 0), DRTs within the entire hemisphere, and solid-angle integral temperature (SIT), we obtain the following results: (1) The optimal viewing azimuth and zenith angles at which the DRTs are the closest to T c are φ s±90° (φ s is the solar azimuth angle) and 45–60°, respectively. (2) The estimation of T c could be further improved once the DRTs from all-direction are available, and the MAE for the SIT that most closely approximated T c is only 0.87 K. (3) The MAE of the SIT that best approximates T c by combining only four DRTs and a kernel-driven model is only slightly higher than that of the specific SIT based on the original DRTs, indicating that the remote estimation of T c using limited DRTs is plausible. These proposed strategies are generally simple and effective, and can help facilitate the estimation of T c and therefore help advance the thermal remote sensing of urban climate and environment.