Dynamics of urban heat island intensity in Lecce, Italy: seasonal, diurnal and heat wave influence

Abstract

This study investigates the impact of Heat Waves (HWs) on Urban Heat Island Intensity (UHII) in Lecce, a Mediterranean city in southern Italy. UHII was assessed using air temperature data from six weather stations over a four-year period (2020–2023). The results indicate that UHII is generally higher in winter and spring, with the ARPA (Environmental Protection Regional Agency) station consistently showing the highest values, particularly in summer, attributed to urban characteristics. The diurnal cycle of UHII reveals a peak in the early morning at most stations, followed by a decrease to near zero or slightly negative values during midday. Evening values then increase and persist throughout the night. Stations surrounded by green areas or located in suburban settings recorded the lowest UHII values. A total of eleven HWs occurred during the study period, with an average duration of 10 days. UHII was significantly more intense during HWs at all stations, with the greatest average observed at the ARPA station (2.60 °C) and the smallest at the LST (Liceo Scientifico Tabacchi) station (0.74 °C). These findings highlight the significant impact of HWs on UHI intensification in Lecce, especially in densely developed areas compared to suburban regions. This study emphasizes the importance of investigating UHII dynamics in Mediterranean cities to develop strategies for mitigating the Urban Heat Island (UHI) effect during extreme heat events.