Quantifying thermo-physiological stress exposure during extreme events: Developing a morphological case study in Istanbul

This study aimed to determine thermal comfort conditions during Extreme Heat Events (EHE), particularly focus on Very Hot Day and Heat Wave Event in Istanbul. The analysis was based on a comprehensive dataset of hourly temperature records collected from six meteorological stations over the period 1991–2021. Subsequently, Land Surface Temperature (LST) was mapped on the basis of EHE days. Finally, specific areas with different street morphologies values from the referenced LST were obtained, enabling the evaluation of heat stress for the EHE day and for the period between 2006 and 2021. The study identified August 5th, 2021 as the day of extreme heat stress in Istanbul. LST obtained for August 5th was divided into three groups: low (23.3 °C), moderate (26 °C), and high (29.3 - 30 °C), and findings regarding heat stress were obtained through thermal indices. Physiologically Equivalent Temperature (PET) values on August 5th, 2021, were significantly higher than the 15-year average, showing a shift from moderate and slight heat stress to strong and extreme heat stress levels. PET values indicated strong heat stress, especially around noon, reaching up to 40.5 °C in lower LST, and extreme heat stress level of 45.7 °C in the afternoon in higher LST. Extreme thermal conditions were generally observed on the right side of streets oriented between 105° and 165° in both regions.