بررسی انطباقی ارتباط شاخص های کالبدی بخش مسکونی با توزیع جزایر حرارتی شهر تبریز (مطالعه موردی مناطق 2 و 8)

Introduction: 
Urban heat islands are one of the most common urban phenomena, and some metropolitan areas, especially city centers, are several degrees warmer than their surrounding areas. Heat islands create difficult environmental conditions for city residents and significantly impact air quality, energy consumption, and human comfort. The urban heat island phenomenon is generally studied in two ways: the atmospheric temperature of different locations is compared, and the ground surface temperature is analyzed using satellite images. Previous studies have demonstrated the usefulness of the ground surface temperature concept for measuring and estimating the amount of radiant energy emitted from the earth's surface, including areas under human construction, vegetation, wasteland, and water, which have been used in this study.
Methodology: In this study, an attempt has been made to use Landsat 8 OLI/TIRS bands initially. Using the Single Channel Algorithm (SCA), the land surface temperature was calculated for two urban districts using ENVI software. The impact of these changes on the physical indicators of the study areas, areas 2 and 8 of Tabriz, has been investigated. The indicators have been stratified in the Arc Map software environment to carry out analytical descriptions.
Results: According to the physical indicators studied, the number and shape of heat islands and the average surface temperature are higher in Region 8 than in Region 2.
Discussion: Study area and data used Tabriz metropolis is the largest city in the northwest region and the third largest city in Iran in terms of area. This city is located in East Azerbaijan province, with an area of about 25056 hectares and 38 degrees, 1 minute to 38 degrees, 8 minutes north latitude, 5 minutes to 46 degrees, and 22 minutes east longitude. In the study area, physical indicators including the total area of the residential infrastructure, the building density of the residential sector, the number of floors of the residential sector, the age of the residential sector structures, the quality of the residential sector structure, and the condition of the residential sector structure in terms of the type of building area used were selected as key indicators and examined to determine the relationship between these indicators and the distribution of heat islands in Tabriz city. In this regard, Landsat 8 OLI/TIRS satellite images were used to extract the land surface temperature.
After preparing the photos, the data preprocessing stage, including geometric and radiometric corrections, was performed in the ENVI software environment to minimize the errors related to the images. Using Arc Map software, maps related to land surface temperature were examined and analyzed comparatively in regions 2 and 8 of Tabriz Municipality regarding physical indicators.
Conclusion::The findings of this study indicate a clear and measurable difference in the average ground surface temperature between Regions 8 and 2 on 05/01/2021, with Region 8 consistently displaying higher surface temperatures. This discrepancy can be attributed to a range of interrelated factors. One of the most significant contributors is the age of the building stock in the two regions. Region 8 contains a higher proportion of buildings older than 30 years compared to Region 2. These aging structures are more likely to lack the modern materials and energy-efficient designs that are increasingly implemented in newer constructions.
In addition to age, the structural standards in Region 8 lag behind those of Region 2. A greater number of buildings in Region 8 fail to meet basic structural and energy-efficiency criteria, while the proportion of acceptable structures in terms of construction quality is significantly lower. This suggests that construction practices and regulatory enforcement have historically been weaker in Region 8, which has resulted in an urban environment that is less resilient to thermal challenges. As a result, there is an urgent need to prioritize adherence to construction and energy standards in Region 8 to mitigate the thermal inefficiencies observed.
Region 8 also exhibits notable differences in the type of structural systems used. A substantial number of buildings in Region 8 are constructed with traditional masonry structures, which are typically less effective at minimizing heat transfer compared to modern materials such as reinforced concrete or steel. This structural characteristic further exacerbates the region’s vulnerability to heat accumulation.
Vertical development patterns further distinguish the two regions. The majority of buildings in Region 8 are limited to four floors or fewer, while Region 2 demonstrates a trend toward taller buildings. This disparity in building heights is significant because taller buildings are often associated with greater wind circulation and a reduction in localized heat accumulation. By contrast, the predominantly low-rise building profile of Region 8 contributes to reduced air circulation and, consequently, a higher retention of heat within the urban environment.
Another critical aspect is the density of buildings and the size of the built infrastructure. Region 8 is characterized by higher population and building densities, as well as smaller average building footprints. This combination creates a more compact urban fabric, which is known to contribute to the intensification of urban heat islands. In Region 2, the presence of larger and taller buildings, combined with lower population and building densities, results in a relatively more dispersed urban layout that is less prone to overheating.
The interplay of these factors—building age, structural standards, density, and vertical development—results in Region 8 experiencing higher ground surface temperatures compared to Region 2. In addition to these urban characteristics, it was observed that the thermal inefficiencies in Region 8 are further exacerbated by the lower quality of construction and the lack of energy-efficient designs. Collectively, these conditions create a feedback loop that intensifies the formation and persistence of heat islands in the region.
From a thermodynamic perspective, most of the heat energy generated in the residential sector is transferred through convection processes. The inefficient dissipation of thermal energy in Region 8, as compared to Region 2, aligns with the observed distribution of heat islands in the two areas. Region 8’s higher building density and older, less efficient structures result in greater heat retention and slower heat dissipation, making the area more susceptible to the adverse effects of elevated surface temperatures.
These findings have significant implications for urban planning and policy development. In light of the observed differences, it is evident that targeted measures are required to address the underlying causes of thermal inefficiencies in Region 8. Such measures could include stricter enforcement of construction and energy standards, retrofitting aging buildings to improve their thermal performance, and promoting the use of modern materials and designs in new constructions. Additionally, urban design strategies aimed at reducing building density, increasing green spaces, and improving air circulation should be prioritized to mitigate the effects of urban heat islands.
In conclusion, the study highlights the critical role of urban morphology, construction quality, and density in influencing ground surface temperatures and the formation of heat islands. The results underscore the need for comprehensive urban planning interventions to optimize energy consumption and improve thermal resilience in regions with aging and substandard infrastructure. By addressing these challenges, policymakers and urban planners can work toward creating more sustainable and livable urban environments, particularly in areas such as Region 8, where the impact of inadequate standards is most pronounced.