Heat risk assessment and response to green infrastructure based on local climate zones

The escalation of thermal risks is attributed to accelerating pace of urbanization. However, assessment and response to green infrastructure with respect to heat risk under different climate and function have been inadequate. This study intends to address these gaps by focusing on local climate zones (LCZs). Firstly, spatial characteristics of heat risk indexes (HRIs) constructed based on heat hazard-exposure-vulnerability for three large cities in 2010, 2015 and 2020 were explored. Secondly, whether HRI cross LCZs have significant differences was examined. Third, proportion and heat contribution of different HRI classes under different LCZs were quantified. Finally, effects of green infrastructure under different LCZs on HRI were analyzed. The results revealed consistent upward trends in the prevalence of sub-high and high HRIs from 2010 to 2015. HRIs exhibited significant spatial aggregation characteristics. Importantly, more than 95.83% of HRIs cross LCZs exhibited significant variations. The HRI for open building type was lower when compared to the compact LCZ types. Additionally, Normalized Difference Vegetation Index (NDVI) had a more pronounced mitigating effect on HRIs in compact high-rise (LCZ 1), compact mid-rise (LCZ 2), open high-rise (LCZ 4) and open mid-rise (LCZ 5). Updating the compact LCZ types to open LCZ types, avoiding configuration of LCZ 1 and 2, and prioritizing the configuration of NDVI enhancement in the existing LCZ 1, 2, 4 and 5, and increasing the amount of greenery by upgrading mono-structures to composite structures consisting of trees, shrubs and grasses and by implementing greening of facade are suggested to alleviate heat risk.