Spatial and seasonal effects of different LCZ types on Urban Heat Islands in a Mediterranean urban area (Beirut, Lebanon)

This study investigates the spatial and seasonal dynamics of the Urban Heat Island (UHI) effect in Beirut, Lebanon, using the Weather Research and Forecasting (WRF) model coupled with the Single Layer Urban Canopy Model (SLUCM). UHI intensity was quantified by comparing a realistic urban simulation with a hypothetical scenario where the city's urban surfaces were replaced with grassland. The model's performance was validated against observations from the Beirut Rafic Hariri International Airport, showing strong positive correlations (r values between 0.74 and 0.9) despite a consistent temperature underestimation of 1.32∘C. The analysis revealed spatial and temporal variation in UHI intensity across Beirut's Local Climate Zones (LCZs). The maximum UHI intensity observed reached 4.5∘C. Industrial and compact high-rise zones (LCZs 10 and 1) consistently exhibited the strongest warming, with average nighttime UHI intensity in these zones calculated at approximately 3.1∘C. Conversely, vegetated and less densely built areas (LCZs 6, 9, and B) demonstrated cooling effects or minimal heating. Seasonal differences were observed, with the most intense UHI episodes occurring in February and October, reaching up to 1.2∘C higher than the summer-peak UHI. Variability in temperature was highest in LCZs with heterogeneous land cover, highlighting that surface diversity is a key factor influencing local microclimates.