Detailed Variations in Urban Surface Temperatures Exploration Based on Unmanned Aerial Vehicle Thermography

Determining the land surface temperature (LST) variations in urban surfaces using high spatiotemporal resolution thermal infrared data is necessary for urban microthermal environmental modeling. An unmanned aerial vehicle (UAV) equipped with a thermal infrared imager was used to monitor the high-precision spatiotemporal variation of LSTs for six typical urban surfaces, including water, tree canopy, grass, brick pavement, asphalt pavement, and marble pavement, in the Jiangning district, Nanjing. An estimation of sensible heat release was further conducted to quantitatively describe the fine characteristics of the LSTs of these surfaces. The factors influencing LST were investigated by correlating LSTs with the meteorological factors. The results showed that there were significant differences in LSTs and sensible heat release for six typical urban surfaces in sunny and cloudy days, respectively. On sunny days, the diurnal variations in different surfaces fluctuated substantially, which was not evident on cloudy days. The artificial surfaces always represented as the main source of sensible heat release. Solar radiation and air temperature, among the meteorological factors, were positively correlated with the LSTs of the surfaces. The air humidity was negatively correlated with the LSTs and played a role in cooling the land surface.