Quantifying the Heat Mitigation Capacity of Green-Blue Infrastructures in the Metropolis of Tehran

The aim of this research is to evaluate the heat mitigation index (HMI) in the Tehran metropolitan area using the Urban Cooling Model (UCM) approach in a spatial framework.UCM produces maps of the Heat Mitigation Index.This index estimates the cooling potential of urban green spaces in a given location, taking into account various parameters such as evapotranspiration, tree shading, albedo, rural reference air temperature, urban heat island intensity, air temperature maximum blending, and maximum cooling distance.The assessment of environmental factors influencing the UCM in the study area revealed that the urban heat island effect was least intense in regions 1, 22, and the northern parts of region 4 of Tehran municipality, where there are scattered trees, shrubs, open low-rise buildings, and water bodies.The temperature differences between the city and the suburbs ranged from 0 to 1.3 degrees Celsius.However, the study area's central parts showed the highest intensity of the urban heat island, particularly in regions 21, 13, and 14.These regions have a dense and compact texture and an expansion of impervious surfaces, resulting in the lowest values of the evapotranspiration index (ranging from 0.12 to 0.45) and albedo (ranging from 0.09 to 0.16).Based on these parameters, the study area's HMI index showed that the cooling capacity varies from 0.08 in the central parts of the city to 0.9 in areas affected by green spaces and water bodies.The maximum cooling capacity index is concentrated in areas with dense and scattered tree cover in the region.On average, these areas have been able to neutralise 2.48 degrees Celsius of the urban heat island effect with a cooling capacity of 63%.The methodology employed in this research can be used as a reference for urban designers in integrating urban cooling approaches and heat island mitigation strategies in urban planning and design.