Heat vulnerability index mapping through principal component analysis and equal weight methods: comparing Spatial patterns at a low urban scale and local climate zones in an arid mid-size South American coastal city

One of the most evident effects of the cities expansions is the increasing urban temperatures, the so-called urban heat islands, affecting more significantly vulnerable populations. In this study, we examine heat vulnerability in Arica, a medium-sized coastal and desert city in Chile, using the Heat Vulnerability Index (HVI) methodology. We compared the performance of two methodological approaches: Principal Component Analysis (PCA) and Equal Weight (EW), as well as how this vulnerability is distributed among local climate zones. The results show that the general spatial pattern of heat vulnerability indices is moderately heterogeneous in the city. The PCA method grouped all indicators into four independent components that explain 71.7% of the total variance. Specifically, the PCA method overestimated vulnerability in the urban core of the city as well as in Cancha Rayada sector, while the EW method overestimated it in peripheral areas due to inherent differences in how each method weighs and processes spatial data. Regarding vulnerability to heat in the local climatic zones (LCZ) of Arica, both methods agreed that the Lightweight lowrise represents the class with the highest levels of vulnerability, notably in areas such as Cancha Rayada and Pedro Blanquier, the districts most susceptible to extreme heat. This study may help to provide results for future research, as well as to carry on adaptation and mitigation strategies for urban planning in Arica, in a context of implementation of the climate change adaptation and mitigation plans in Chile and the necessary actions at the urban level.