Nocturnal Surface Urban Heat Island Dynamics in a Semi-Arid Mediterranean City: Evidence from Damascus

Abstract

Although nocturnal surface urban heat islands, which impede physiological recovery during rest, have been characterized in many cities worldwide, Syria’s capital, Damascus, situated in the Eastern Mediterranean region, remains without a quantitative, multi-time assessment of its nocturnal thermal behavior. This study delivers that assessment for the city and its surroundings during 2023–2025, using 138 MOD11A2 (Collection 6.1) nighttime scenes processed within Google Earth Engine and Python. Six complementary axes were integrated: the thermal gradient across functional classes, the anomaly field, SUHI intensity (SUHII) against three rural references, the Getis–Ord Gi* statistic, a multivariate topographic regression, and the Urban Thermal Field Variance Index (UTFVI). A consistent nocturnal gradient emerged (urban: 16.28 °C; bare land: 14.74 °C), with an annual intensity of 1.50 °C, about 36% above the global mean. A genuine seasonal crossover between the bare-land and agricultural references occurred in June, reflecting the phenological cycle of soil thermal inertia. Topography explained only ~10% of the spatial variance (R2 = 0.102), and the topographically corrected intensity retained about 90% of its original value. The Gi* statistic identified a single central hot spot (p < 0.01 after false-discovery-rate correction, with significance adjusted for spatial autocorrelation) that coincided spatially with the “poor” thermal-stress nucleus delineated by UTFVI, covering 11.92% of the study area. The convergence of these complementary lines of evidence confirms the persistence of the phenomenon and provides a scientific basis for climate-aware urban planning in semi-arid Mediterranean cities.