Spatial and temporal dynamics of surface urban heat islands in Iran

The surface urban heat phenomenon and global warming share a mutual relationship, representing major environmental challenges of the 21st century. This study examines spatio-temporal variations of Surface Urban Heat Islands (SUHIs) in 16 major Iranian cities across different climatic regions to identify areas with intense surface warming and explore their relationship with urban characteristics. MODIS Land Surface Temperature (LST) data from 2001 to 2020 and Landsat-derived NDVI were used to assess vegetation cover. Temporal trends were quantified using the Mann – Kendall and linear regression methods, and Ward’s hierarchical clustering classified cities based on SUHI intensity patterns. The results showed four and six main clusters during daytime and night-time, respectively. The Surface Urban Cool Island (UCI) effect dominated during the day, while SUHI prevailed at night. UCI mainly occurred in urban areas surrounded by barren lands in arid and semi-arid regions. LST trends confirmed UCI formation through decreasing daytime temperatures, while night-time SUHI exhibited higher temperatures at city centres. NDVI time-series analysis indicated minimal vegetation change during the 17-year period. Overall, the spatial pattern of LST across Iran is influenced by elevation, latitude, vegetation, and proximity to the sea under different climatic conditions.