Background and Objective

Rapid urbanization and the intensification of human activities in recent decades have contributed to the intensification of the urban heat island phenomenon and its associated consequences, including increased energy consumption, reduced air quality, and adverse effects on public health. Among these factors, geometric urban morphology variables, as artificial and potentially manageable characteristics, play an important role in explaining variations in land surface temperature (LST). Therefore, understanding the relationship between the physical and geometric characteristics of the urban fabric and land surface temperature can contribute to climate-responsive urban planning and design. The aim of this study is to analyze the relationship between geometric indicators of urban form, including mean parcel size, built-up surface ratio, weighted average number of floors, and urban canyon index, and land surface temperature at the urban-block scale in two districts of Tehran with contrasting development patterns: District 18, characterized by organic and compact growth, and District 22, characterized by planned development and high-rise construction.

Materials and Methods

This study utilized Landsat-8 satellite imagery with a spatial resolution of 30 m, along with a set of quantitative urban morphology indicators, including mean parcel size, built-up surface ratio, weighted average number of floors, and the height-to-width ratio of urban canyons (H/W), at the urban-block scale. In the first stage, the urban morphology indicators were selected based on previous studies and the feasibility and availability of the required data, and were calculated at the urban-block scale. Subsequently, land surface temperature (LST) was extracted from daily Landsat-8 imagery for the summer and winter seasons of 2021, and LST maps of the study areas were generated using the Google Earth Engine platform. Finally, to examine the relationship between the urban morphology indicators and mean land surface temperature, a multiple linear regression model based on the Ordinary Least Squares (OLS) method was applied separately for the summer and winter seasons.

Results and Discussion

The results of the model indicated that the relationship between the morphological indicators and mean land surface temperature was stronger in summer than in winter. Among the examined indicators, the urban canyon index exhibited the strongest negative relationship with mean land surface temperature in both seasons, with coefficients of -0.699 in summer and -0.151 in winter. The built-up surface ratio also showed a negative relationship with land surface temperature; approximately, each unit increase in this indicator was associated with a decrease of about 0.0367 °C in mean summer land surface temperature. Mean parcel size also showed a negative but very weak relationship with land surface temperature, with a coefficient of approximately -0.00006. In contrast, the weighted average number of floors did not show a significant relationship with variations in mean land surface temperature.

Conclusion

The findings of this study indicate that geometric urban morphology indicators are associated with land surface temperature in the studied areas of Tehran, and that the strength of these relationships is greater in summer than in winter. Among the examined indicators, the urban canyon index (H/W) exhibited the strongest negative relationship with mean land surface temperature in both seasons, while the built-up surface ratio also showed a negative relationship with temperature. Mean parcel size showed a negative but very weak relationship with land surface temperature, whereas the weighted average number of floors did not show a significant relationship with variations in mean temperature. These findings indicate that the geometry of inter-building spaces, the extent of built-up surfaces, and the physical characteristics of urban parcels can contribute to explaining the spatial pattern of land surface temperature. Therefore, greater attention to urban morphology indicators, particularly urban canyon geometry and the extent of built-up surfaces, in urban planning and design processes can contribute to the development of climate-responsive policies and the reduction of the thermal consequences of urban development in Tehran and other metropolitan areas.