Satellite-Derived Subsurface Urban Heat Island

• Published in: Environmental science & technology Vol. 48; no. 20; pp. 12134 - 12140
• Main Authors: Zhan, Wenfeng, Ju, Weimin, Hai, Shuoping, Ferguson, Grant, Quan, Jinling, Tang, Chaosheng, Guo, Zhen, Kong, Fanhua
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 21.10.2014
• Subjects: Cities - statistics & numerical data; Convection, turbulence, diffusion. Boundary layer structure and dynamics; Earth, ocean, space; Environmental Monitoring; Exact sciences and technology; External geophysics; Heat; Hot Temperature; Meteorology; Models, Theoretical; Remote Sensing Technology; Rural areas; Seasons; Temperature; Urban heat islands; Far East; Asia; China; Beijing China; China, People's Rep., Beijing; Spectroradiometry; Moderate resolution imaging spectroradiometer; Megacity; Space remote sensing; Satellite observation; urban areas; Microclimate; Urban heat island; Urban climate
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es5021185

The subsurface urban heat island (SubUHI) is one part of the overall UHI specifying the relative warmth of urban ground temperatures against the rural background. To combat the challenge on measuring extensive underground temperatures with in situ instruments, we utilized satellite-based moderate-resolution imaging spectroradiometer data to reconstruct the subsurface thermal field over the Beijing metropolis through a three-time-scale model. The results show the SubUHI’s high spatial heterogeneity. Within the depths shallower than 0.5 m, the SubUHI dominates along the depth profiles and analyses imply the moments for the SubUHI intensity reaching first and second extremes during a diurnal temperature cycle are delayed about 3.25 and 1.97 h per 0.1 m, respectively. At depths shallower than 0.05 m in particular, there is a subsurface urban cool island (UCI) in spring daytime, mainly owing to the surface UCI that occurs in this period. At depths between 0.5 and 10 m, the time for the SubUHI intensity getting to its extremes during an annual temperature cycle is lagged 26.2 days per meter. Within these depths, the SubUHI prevails without exception, with an average intensity of 4.3 K, varying from 3.2 to 5.3 K.