Urban Heat Under Mediterranean Skies: Comparing Surface Heat Island Patterns in Malta and Zaragoza

Sammanfattning

This study investigates the spatiotemporal development of the Surface Urban Heat Island (SUHI) in Malta, and compares it with Zaragoza, Spain, as an inland reference site of the same Köppen climate classification. High-resolution summer Land Surface Temperature (LST) data from 2013 to 2025, along with Impervious Surface Area (ISA), Land Use/Land Cover (LULC), and NDVI data were used to analyse the SUHI development in the study area. In addition, MODIS day and nighttime LST data from 2003 to 2025 were used to examine longer-term, diurnal SUHI trends. The results obtained, show that Malta does not display a conventional daytime SUHI signal, as areas defined as rural with ISA were generally warmer than the urban ones, with an urban-rural LST difference of -1.33 °C. In contrast, Zaragoza showed consistently positive urban-rural LST differences of +2.11 °C, indicating a clearer inland SUHI pattern. It was found that MODIS nighttime analysis has resulted in a significant UHI increase in both study areas, +0.019 °C/year in Malta and +0.018 °C/year in Zaragoza. This suggests that urban heat retention is more clearly expressed at night than during the day. Overall, the findings show SUHI development cannot be explained by urbanisation alone; research suggests that factors such as local climate, maritime exposure, vegetation conditions, dry rural surfaces & their composition, along with time of observation, strongly influence how urban heat is expressed.