Spatial-temporal variations of surface urban heat island: An application of local climate zone into large Chinese cities

Abstract

The land surface temperature (LST)—based surface urban heat island (SUHI) is suitable for exploring thermal environments at large scales. Despite a few studies focused on the intra-urban SUHI intensity (SUHII) of a single city or cities with similar climates by adopting the local climate zone (LCZ) scheme, exploration of the spatial-temporal characteristics of the intra-urban SUHII and SUHI extent (SUHIE) is still limited across diverse climate zones. This study aims to (1) propose an improved LCZ mapping method to refine historical LCZ data for highly urbanized Chinese cities; (2) put forward a buffer-based approach to quantify the actual area affected by the SUHI; (3) investigate the spatial-temporal pattern of SUHI in large Chinese cities. The results show that the intra-urban SUHII varies across seasons, times and background climate—highest during summer days and lowest during winter days, decreasing with background climate becoming warm and wet. SUHIE displays an apparent temporal pattern similar to SUHII and has an increasing trend, but it relates more to urban areas (particularly the area of LCZ 1) than background climate. Due to the positive impact of LCZ 1 on both SUHII and SUHIE, its area should be strictly restricted in design practice. Although LCZ 4 has the advantage over LCZ 1 in mitigating SUHII, it correlates positively to SUHI expansion. From a planning perspective, a balance between the reduction of SUHII and SUHIE should be considered. This study provides evidence-based planning recommendations to mitigate urban heat and create a comfortable built environment.