Investigation of Tabriz urban heat islands with urban livability approach

Introduction
Urban heat islands (UHIs) are a global issue and threaten the performance of cities and urban environments. In
recent years, due to the greater concentration of urbanization on one hand and global warming on the other hand,
we have witnessed widespread changes in the urban environment. In other words, urban biodiversity in
metropolitan areas has been threatened by surface urban heat islands. (SUHI) is one of the major topics in urban
climate studies; the surface has a complex structure that can be a combination of vegetation, water and
impermeable surfaces and soil. As a result, the land surface temperature (LST) has a great deal of time-space
variation. This study investigates the biodiversity approach of urban heat islands in Tabriz.
Materials and Methods
The processes used to calculate LST in this study are as follows
1) Convert digital image values to spectral radians
2) Conversion of spectral radiance to brightness temperature.
3) Convert brightness temperature to kinetic temperature.
After calculating the LST from the Landsat 7 satellite ETM + band, the Fractal Net Evolution Approach (FNEA)
is used for LST segmentation. Finally, the Environmental Criticality Index (ECI) was used to study urban viability.
Results and Discussion
It provides statistical characteristics for the 15 year period of Landsat 7 ETM + satellite images for Tabriz. As
shown in the table, the average land surface temperature for the city of Tabriz during the period from 1999 to
2013 is between 30 and 43 degrees Celsius. The lowest LST recorded in Tabriz was 13.40 degrees Celsius on
7.20.2002 and the highest land surface temperature was calculated with 43.94 degrees Celsius on 7.7.2010. The
average land surface temperature in most selected images is between 34 and 37 degrees Celsius, and the mean
deviation for LST in this metropolis is about 3 degrees Celsius, which plays an important role in the temperature
distribution of Tabriz.
Conclusion
The results showed signs of intensifying effects of SUHI, especially in the period 2013–2010, when urbanization
was higher. The maximum deviation from the standard was observed during the study period from 2010 to 2013,
with a standard deviation of 4.1 in 2010 and a sensitivity of 4.50 degrees Celsius in 2013, the final year of the
survey. The minimum LST was calculated to be 13.40 degrees Celsius in 2002 and its maximum with 43.94
degrees Celsius in 2010. Significant positive correlation was observed between LST and urban areas, confirming
the strong influence of urbanization on SUHI formation in Tabriz. Vegetation and its continuous improvement
help reduce the effects of SUHI warming. Important thermal islands of Tabriz were identified using Landsat 7
ETM + sensor data including: Tabriz Airport (the largest thermal island in the city); Southwest Industrial Areas;
Railway Station, Tabriz Market, High Residential Areas Such as MOLAZINAL and Tabriz metropolitan areas.
The ECI map produced in this study also shows the close relationship between LST and NDVI. Therefore, urban
green spaces are important components in the concept of urban sustainability development.