Optimizing the urban thermal environment at local scale: a case study in Wuhan, China

Abstract

The urban thermal environment deteriorates with increasing frequency of extreme heat events in cities. Conventionally, the Urban Heat Island (UHI) effect only reflects the temperature difference between the city and its rural surroundings. This scale of analysis is often too broad to help devise mitigation strategies, which are typically implemented at a more local scale within the sphere of urban planning and design. In this research, the city of Wuhan, China, is taken as an example. Through quantitative measurements, a workflow is proposed to mitigate the surface UHI of Wuhan, locally. Also, the satellite images of the MODerate-resolution Imaging Spectroradiometer and Landsat-7 ETM+ are used for technical purposes, and the K-means clustering is applied to classify the Local Climate Zone (LCZ). Further, the Local Scale Urban Heat Island (LSUHI) is captured through morphological parameters, such as Multi-Scale Shape Index (MSSI) based upon the latent Land Surface Temperature (LST) pattern. The mitigation process is organized hierarchically and prioritized by the combination of LCZ and LSUHI. Based on this, Wuhan is divided into seven LCZs and the LSUHI, in the mean time, can be detected by morphological parameters. We present the corresponding quantitative planning advice for places with higher heat threats in the city. This research is conducted on urban microclimate and urban planning on at least two levels: (1) the reduced study scale of urban thermal environment and (2) a planning-driven workflow of urban thermal environment optimization.