Assessing heat exposure to extreme temperatures in urban areas using the Local Climate Zones classification

Abstract. Trends of extreme temperature episodes in cities are increasing (in frequency, magnitude and duration) due to regional climate change in interaction with the urban effects. Urban morphologies and thermal properties of the materials used to build them are factors that influence the spatial and temporal climate variability and becomes one of the main reasons for the climatic singularity of cities. This paper presents a proposal to evaluate the urban and peri-urban effect on extreme temperatures exposure in Barcelona (Spain), using the Local Climate Zone (LCZ) framework as a base statement, that allows the comparison with other cities of the world characterized using this criterion. LCZs were introduced as input of the high resolution UrbClim model (100 m spatial resolution) to create the daily temperatures (median and maximum) series for summer (JJA) during the period 1987 to 2016, pixel by pixel, in order to create a cartography of extremes. Using the relationship between mortality due to high temperatures and the temperature distribution, the heat exposure of each LCZ was obtained. Methodological results of the paper show the improvement obtained when LCZs were mapped through a combination of two techniques (from Land Cover/Land Use maps and from WUDAPT method), as well as proposes a methodology to obtain the exposure to high temperatures of different LCZs on urban and peri-urban areas. In the case of Barcelona, the distribution of temperatures for the 90th percentile (about 3–4 °C compared to average conditions) leads to an increase in the relative risk of mortality of 80 %.