High resolution WRF modeling of the long-term effects of peri-urban forest fires on the local micro-climate in Athens, Greece.

Mediterranean cities are highly susceptible to climate change due to their geographic location, climatic conditions, and socio-economic factors. The Mediterranean region is considered a climate change hotspot, and cities in the region are warming 20% faster than the global average, with extreme heatwaves becoming more frequent and intense. Rising temperatures and prolonged droughts increase the frequency and intensity of wildfires in peri-urban forests and green belts, with long-term effects on the local urban microclimate, altering temperature regulation, humidity levels, and wind patterns. The loss of peri-urban forests disrupts the natural cooling effect provided by tree cover and evapotranspiration, resulting in increased urban heat island (UHI) intensity, higher surface and air temperatures, and reduced nighttime cooling. We investigate these effects on the local microclimate in the city of Athens, Greece, which is one of Europe’s largest Metropolitan complexes with a population of approximately 3.7 million inhabitants. In the past decade, Athens has experienced an unprecedented number of peri-urban forest fires, attributable to both global warming and growing urbanization. Heat waves are nowadays common during the summer months, with temperatures exceeding 40°C, which strongly increases the thermal risk and vulnerability of the surrounding forest cover. We use high-resolution WRF simulations (1km horizontal grid) driven with ERA-5 re-analysis data, to produce surface temperature and humidity maps in the city of Athens and the surrounding areas (Region of Attiki), with and without forest cover lost during this period. Results indicate strong localized effects with respect to surface temperature and humidity fields driven by land cover changes due to forest loss. We test the effects produced using different meteorological conditions, confirming long range impacts which affect the urban microclimate. Understanding these impacts is crucial for urban planning and climate adaptation strategies, emphasizing the need for reforestation, sustainable land management, and fire-resistant landscape designs.