Modeling intra-urban differences in thermal environments and heat stress based on local climate zones in central Wuhan

Abstract

Urban morphology exerts a strong influence on urban thermal environments, and local climate zones (LCZs) explicitly link urban morphology with microclimate. However, how temperature, humidity, and thermal comfort vary across different LCZs from a modeling perspective remains understudied. Here, we first developed a high-precision LCZs map of central Wuhan using a combination of GIS- and RS methods, and then simulated intra-urban differences in 2-m air temperature (T2), water vapor mixing ration (Q2), and heat index (HI) through incorporation of the LCZs map into a mesoscale model coupled with an urban canopy model. Results showed that the urban core area was dominated by the compact forms (i.e., LCZs 1–3), surrounded by the open forms (i.e., LCZs 4–6) and the natural/semi-natural types on the periphery (i.e., LCZs D and G). The intra-urban variability of nighttime T2 was up to 2.5 °C and daytime Q2 up to 0.9 g/kg across LCZs of the artificial built types. The compact forms were hotter but drier than the corresponding open forms, and LCZ 9 had the lowest T2 but highest Q2. HI exceeded the danger line (i.e., 41 °C) during 12:00–21:00 LST across the LCZs, with the intra-urban variability of HI in the daytime smaller than in the nighttime. That is, HI was largely influenced by Q2 in the daytime but mainly determined by T2 in the nighttime. Findings of this study highlighted that mitigation measures should be taken to alleviate the pressure of high temperature and humidity on human thermal comfort.