Urban Green Network Design as an Adaptation Strategy of Mediterranean Cities to Rising Temperatures

Rising temperatures within the urban context, as a result of climate change and the Urban Heat Island effect, have deteriorated thermal comfort conditions in outdoor urban spaces, especially during hot, Mediterranean summer days. This study investigates the potential cooling effects of integrating individual urban green spaces into a connected network, with the aim of improving thermal conditions in public areas. Thermal conditions of an 800 m2 urban area in the city of Athens, Greece, were evaluated for a typical summer day using the environmental model ENVI-met. Based on an assessment of the current microclimatic conditions, a potential thermal adaptation strategy was developed, aiming to redesign the study area as a network of green-blue infrastructure. This includes a 1.5 km walking route connecting various spaces, such as squares, parks, and schools. Air temperature (Tair) and the bioclimatic index PET (Physiologically Equivalent Temperature) were used to evaluate the thermal conditions of the study area. In addition, a new function of the ENVI-met model, Dynamic Comfort, has been implemented to calculate the dynamic Physiological Equivalent Temperature (dPET) index for the selected route. The results revealed significant Tair and PET reductions compared to the current layout, indicating that the integration of open spaces into a network of green-blue infrastructure can improve thermal conditions and reduce the hazardous effects of thermal stress on people. Some notable results include the spatial and temporal decrease of the Tair of up to 6 °C, mainly in the proximity of buildings and fountains. Similarly, PET values decreased mainly by 3 to 5 °C. The Dynamic PET showed a slight reduction during the hours of maximum temperature and a higher decrease during the evening, ranging from 1 to 2 °C.