Airborne and Terrestrial Observations of the Thermal Environment of Urban Areas Surrounding a High-Rise Building during the Japanese Winter

We investigated the distribution of air temperature (T_a) and the factors affecting it in low-rise areas surrounding an isolated high-rise building during the Japanese winter. The study site was the central part of a regional city in Japan (36°5' N, 140°12' E), lying north-east of the Tokyo metropolitan area. The daytime surface temperature (T_s) in the shade is generally considered to be comparable to T_a; however, according to airborne remote sensing conducted in December 2009 where a multi-spectral scanner was installed on a fixed-wing aircraft, T_s for pavements in the shade of a high-rise building was significantly lower than T_a of sub-urban areas, indicating an influence of cold storage on T_s. Then, we conducted mobile observations using instruments (thermocouple, four component radiometer, and so on) installed on a bicycle in January 2016 to investigate the detailed distribution of T_a and the factors affecting it. The results showed the T_a over the pavements in the shade of the high-rise building was lower than the T_a of sunlit areas in the same urban area by -2 °C and lower than the T_a of sub-urban areas by -1-1.5 °C, although the advection effect was large due to strong winds around the building. In conclusion, a locally lower T_a compared to the surrounding areas can develop during the day in winter, even in spaces that are open to areas beyond the canopy.