Mapping Urban Heat Vulnerability of Extreme Heat in Hangzhou via Comparing Two Approaches

Extreme heat is the leading cause of heat-related mortality around the world. Extracting heat vulnerability information from the urban complexity system is crucial for urban health studies. Using heat vulnerability index (HVI) is the most common approach for urban planners to locate the places with high vulnerability for intervention and protection. Previous studies have demonstrated that HVI can play a vital role in determining which areas are at risk of heat-related deaths. Both equal weight approach (EWA) and principal component analysis (PCA) are the conventional methods to aggregate indicators to HVI. However, seldom studies have compared the differences between these two approaches in estimating HVI. In this paper, we evaluated the HVIs in Hangzhou in 2013, employing EWA and PCA, and assessed the accuracies of these two HVIs by using heat-related deaths. Our results show that both HVI maps showed that areas with high vulnerability are located in the central area while those with low vulnerability are located in the suburban area. The comparison between HVI EWA and HVI PCA shows significantly different spatial distributions, which is caused by the various weight factors in EWA and PCA. The relationship between HVI EWA and heat-related deaths performs better than the relationship between HVI PCA and deaths, implying EWA could be a better method to evaluate heat vulnerability than PCA. The HVI EWA can provide a spatial distribution of heat vulnerability at intracity to direct heat adaptation and emergency capacity planning.