Analysis of the Impact of local Climate Zones on Environmental Thermal Loads of Tehran

Local Climate Zones (LCZs), shaped by the physical structure, spatial layout, and surface characteristics of cities, correspond to distinct thermal environments ranging from urban heat islands (UHIs) to localized cool pockets. In this study, four sets of Landsat 8 satellite images from 2022—representing all four seasons—were used to classify Tehran’s LCZs. A total of seventeen LCZ types were identified across Tehran and its surrounding suburbs. Among the urban LCZ classes, the open high‑rise built‑up zone (LCZ 10) occupied the largest proportion of the study area (10.88%). This was followed by compact mid‑rise, sparsely built, open mid‑rise, and industrial zones (LCZ 2, 7, 5, and 8). These classes were concentrated primarily in the central districts, where nighttime temperatures were highest, forming the core of Tehran’s UHI with temperatures ranging from 14 to 16°C. In contrast, natural LCZs located around the city exhibited significantly lower temperatures, forming cool pockets with averages between –1 and 3°C. Compact built‑up zones—characterized by low sky view factor (SVF), high impervious surface ratios, limited natural ventilation, and strong solar radiation absorption—were identified as the main contributors to Tehran’s UHI. Conversely, water bodies, dense and scattered green spaces, and open areas with high air circulation functioned as effective cooling zones within the urban fabric. These findings provide valuable insights for urban climate researchers and planners, enhancing understanding of how urban form influences thermal patterns and offering guidance for strategies aimed at improving thermal comfort and mitigating UHI effects in rapidly growing cities.
 
Extended Abstract
1-Introduction
Urbanization and city development in recent decades have caused substantial changes in land use and land cover, significantly influencing urban climate, energy consumption, public health, and temperature dynamics. Morphological and anthropogenic transformations—particularly increased building density and the reduction of green spaces—have intensified the formation of urban heat islands (UHI), a phenomenon further amplified by global climate change. Accurate identification of UHI‑affected areas requires localized climate classification methods capable of capturing fine‑scale urban characteristics. One of the most widely adopted approaches in this context is the Local Climate Zones (LCZ) framework, introduced by Stewart and Oke (2012). LCZ enables the classification of urban areas based on their physical, morphological, and functional attributes. By integrating building height, urban density, land‑cover composition, and environmental indices, the LCZ system provides a comprehensive basis for analyzing local climate behavior and its influence on land surface temperature (LST) and UHI intensity. This study aims to identify the LCZs of Tehran and examine their effects on UHI intensity and spatial distribution, with particular emphasis on heat load and the physical and functional characteristics of the urban fabric at a local scale. Tehran—covering approximately 1,987 km² and characterized by a semi‑arid climate and diverse topography—offers an ideal case study for exploring the interactions between urban morphology and thermal processes. Rapid urban expansion, dense construction patterns, and the ongoing decline of green cover, especially in central districts, have created conditions conducive to the development of strong UHI effects.
 
2-Materials and Methods
The study utilized four Landsat 8 OLI–Thermal satellite images from 2022, representing different seasons (February 13, April 18, August 24, and November 20), with spatial resolutions ranging from 30 to 100 meters and cloud cover below 10%. The images were preprocessed and clipped to the study area, and sample points for LCZ classification were collected using Google Earth. High‑accuracy training samples were then prepared and applied in a supervised classification workflow using SAGA‑GIS. Morphological indices—including Sky View Factor (SVF), surface absorption (SA), albedo, percentage of permeable surfaces (PSF), and impermeable surfaces (ISF)—were calculated for each LCZ class. Additionally, land surface temperature (LST) data from the MODIS sensor were used to assess seasonal and diurnal temperature variations and to examine the relationship between LCZ types and urban heat island (UHI) intensity.
 
3- Results and Discussion
The LCZ classification identified 17 distinct classes of human‑made structures and natural land cover across Tehran. Bare land was the most extensive class, covering 35.13% of the study area, while LCZ G represented the smallest proportion at only 0.07%. Dense urban LCZs (LCZ 1–LCZ 3), characterized by high building density, low sky view factor (SVF), and a high proportion of impervious surfaces, formed the core of the nighttime urban heat island (UHI), with temperatures ranging from 14 to 16°C in the central districts. In contrast, natural and vegetated LCZs—such as LCZ A and LCZ B—exhibited substantially lower surface temperatures. Daytime and nighttime land surface temperature (LST) analyses showed that daytime hotspots were concentrated in industrial zones, storage facilities, and southern slopes, whereas nighttime UHI intensified in high‑density built‑up areas due to heat retention in construction materials and restricted natural ventilation. SVF demonstrated a cooling effect during the day by increasing shading and reducing heat absorption; however, at night, low SVF contributed to heat entrapment and amplified UHI intensity. Impervious surface fraction (ISF) and surface absorption (SA) exhibited strong positive correlations with UHI intensity, while vegetation cover (NDVI) played a significant cooling role. Areas with permeable surface fractions (PSF) below 30% consistently emerged as nighttime thermal hotspots. Overall, the findings indicate that a combination of urban physical and morphological characteristics—including building density and height, SVF, albedo, and the balance between permeable and impermeable surfaces—strongly shapes the spatial distribution and intensity of UHI in Tehran. Although dense high‑rise zones (LCZ 1) occupy only 1.38% of the study area, they function as the primary nighttime UHI cores. Conversely, tall but more widely spaced buildings generate lower UHI intensity under similar density conditions due to enhanced ventilation and shading.
 
4- Conclusion
These results are consistent with previous research conducted in Iran and other cities worldwide, underscoring the value of the LCZ framework for detailed and accurate urban climate analysis. By integrating multi‑seasonal satellite observations with three‑dimensional urban morphological indices, this study establishes a comprehensive approach to LCZ classification in Tehran, enabling simultaneous evaluation of urban structure, function, and UHI dynamics. The findings offer practical guidance for urban planning, low‑carbon urban design, and UHI mitigation efforts. Policy measures informed by LCZ insights—such as expanding urban green cover, adopting high‑albedo construction materials, creating ventilation corridors, and increasing permeable surface areas—are recommended to reduce heat load and enhance urban energy resilience in Tehran and comparable metropolitan regions.