Studying the combined method in identifying Urban Heat Islands and their Mitigation via Urban Green Spaces (case study: Isfahan City)

The urban heat island phenomenon is one of the challenges with which most metropolises have been struggling due to unplanned city expansions. Multiple factors have led to the emergence and escalation of this phenomenon, which can be classified into three main categories: the macro-climate of the region, materials used at urban fabric and urban texture. Various suggestions have been given by experts in this area to reduce the severity of this phenomenon and improve the urban microclimate. However, as the phenomenon is different in each city or metropolitan area, various location-specific solutions will be offered to reduce the factors contributing to the phenomenon. The study uses satellite data, including images of the Landsat satellite on July 18, 2015, as well as the overnight satellite images of Modis and the GIS, along with land data from the metropolitan weather stations closest to the selected simulation area where thermal islands were examined. In this regard, the extent of the impact of different uses on the formation and severity of thermal islands in Isfahan was investigated. Based on the findings, applicable suggestions in the field of urban activity are made with an emphasis on the green space.
In this paper, on the city level, the main green spaces including green spaces of urban streets and different types of urban parks were examined with regard to their geographical location in terms of the three categories of surface temperature (approximate 24-35°C, 35-40°C, and 40-51°C) and the applied map of each of these categories were developed. Accordingly, at the city level, the temperature in 10% of urban green spaces was above the normal, the temperature in 15% of urban green spaces was in the normal range, and the temperature in 3% of these spaces was lower than the nornal range.
The Abbas Abad area was studied in terms of urban usage through a simulation of the effect of green spaces, especially green spaces on the boundaries of the roads on the urban microclimate. This area is one of the areas with the most abundant, old green space in the city. In this regard, an urban green space with old trees was selected in the historical fabric of Isfahan and was modeled using Envi-Met. The simulation results for summer 2015 indicate that, despite the close proximity of the three selected points, about 1°C of difference is seen in the temperature of the three spots. The proximity of the water bodies, and green spaces in particular, is one of the main factors. Additionally, the ground data follows the pattern of simulations points as well. Therefore, different scenarios are proposed for the presence of green spaces and evaluated through simulation. The results of this paper show that small green spaces, if designed based on scientific principles, can have a good effect on the thermal effects of heat islands on the small scale. Also, because of the large scale of urban areas, the combined methods proposed in this study can lead to the application of measures to reduce the negative effects of heat islands for urban management.