Urban livability
Zeinab Kia; Aliakbar Shamsipour; Ghasem Azizi
Abstract
Highlights
- Tehran exhibits significant climatic diversity due to variations in elevation, morphology, and physical features.
- The geomorphological characteristics of Tehran's substratum play a critical role in shaping homogeneous climate response units.
- The city's compact urban texture and developmental ...
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Highlights
- Tehran exhibits significant climatic diversity due to variations in elevation, morphology, and physical features.
- The geomorphological characteristics of Tehran's substratum play a critical role in shaping homogeneous climate response units.
- The city's compact urban texture and developmental patterns contribute significantly to the formation of Tehran's urban heat island.
- The climate response units of Tehran are influenced by elevation, surface morphology, and urbanization patterns.
- The middle strip of Tehran, featuring hills and constructed parks, creates distinct local climatic conditions.
Introduction
Understanding the natural characteristics of urban areas, especially their climatic features, is crucial for effective land management. Urban climate plays a fundamental role in shaping ventilation patterns, air quality, and thermal comfort. To enhance urban planning strategies, a suitable climatic classification system is essential for distinguishing different zones based on their environmental conditions. Climatic zoning facilitates the identification of distinct climatic features, enabling region-specific planning and management.
Traditional climate zoning methods are insufficient for modern urban environments due to variations in land use, land cover, urban geometry, and structure. This research employs an applied approach, using descriptive and analytical methodologies. The study integrates multiple spatial data layers, including digital elevation models, land use/cover, building density, green spaces, and hydrographic networks, to classify urban climate zones effectively. These parameters provide a comprehensive understanding of Tehran's climatic conditions and their spatial distribution.
Study Area
Tehran, spanning 615 square kilometers, is situated between mountainous zones and arid plains, leading to diverse climatic conditions. The city's climate is primarily influenced by its topography, with the northern highlands experiencing more favorable conditions than the central and southern low-altitude plains.
Local climatic differences arise due to varying land uses, such as green spaces, barren lands, asphalt surfaces, and residential zones. Building density significantly impacts the urban climate, contributing to distinct microclimatic conditions across different localities. The city's morphology and topography play a decisive role in shaping its climatic response units.
Discussion
A geomorphological map provides valuable insights into the shape, structure, and texture of Tehran’s urban landscape. This map illustrates the relationship between natural features, built environments, and climatic conditions. Different neighborhoods within Tehran exhibit unique topographic characteristics, construction patterns, traffic densities, and accessibility, all of which influence local climate variations.
Key homogeneous climate response units in Tehran include mountains (class 3), green spaces (class 16), and riverbeds/lakes (class 17). These units contribute positively to reducing air temperature, enhancing air quality, and promoting natural ventilation. Preserving these areas is crucial for mitigating urban heat island effects and improving urban climate resilience.
To assess Tehran’s climate at a localized scale, topographic and urban structural parameters were analyzed. First, the spatial distribution of building density was classified into five distinct groups. Subsequently, a geomorphological map of Tehran was generated, identifying ten morphological classes. By integrating building density and urban geomorphology data, a homogeneous climate response unit (HCR) map was developed. This map serves as a vital tool for understanding and managing Tehran’s urban climate.
Conclusion
This research introduces a novel approach to urban climate zoning, previously applied in Lisbon, Portugal, for classifying urban climatic conditions. Central Tehran exhibits high building density, limited green spaces, and pronounced urban heat island effects. The primary factors contributing to the urban heat island phenomenon include high population density, intensified urban activities, and dense construction patterns.
The geomorphological analysis highlights that central and southern Tehran, particularly districts with minimal green spaces (e.g., District 9), suffer from poor air quality and inadequate natural ventilation. These areas exhibit unfavorable climatic conditions due to high pollution levels, urban congestion, and limited airflow. Conversely, northern Tehran (e.g., Districts 1 and 4) benefits from superior air quality, attributed to its proximity to mountains, river valleys, and extensive green spaces.
The prevailing wind direction in Tehran originates from the west, influencing pollutant dispersion patterns. Industrial concentrations in the western parts of the city exacerbate pollution levels in adjacent areas. Consequently, central and southern Tehran require strategic urban interventions to enhance climatic conditions. Recommendations include:
- Integrating green spaces on building facades and streets.
- Establishing water features such as ponds and fountains to moderate air temperature.
- Utilizing reflective and cool materials in urban surfaces to mitigate heat accumulation.
- Expanding green areas to improve air quality and humidity levels.
- Regulating urban expansion to prevent excessive development in climatically vulnerable zones.
- Designing transportation networks to facilitate natural air circulation.
In conclusion, effective climate zoning strategies are essential for sustainable urban development in Tehran. Implementing targeted climate-responsive urban planning measures can significantly improve air quality, thermal comfort, and overall environmental conditions in the city.
Urban Sustainability
Saeed Sepasi Zangiabadi; Aliakbar Shamsipour; Ali Hosseini
Abstract
Highlights- Climatic zoning of Tehran was conducted using the latest and most accurate method available.- This climatic zoning used the processing of Landsat 8 satellite images and sampling in Google Earth.- 17 climatic zones were obtained according to physical characteristics and land surface cover.- ...
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Highlights- Climatic zoning of Tehran was conducted using the latest and most accurate method available.- This climatic zoning used the processing of Landsat 8 satellite images and sampling in Google Earth.- 17 climatic zones were obtained according to physical characteristics and land surface cover.- The LCZ model focuses on the thermal loads of the city, which are affected by building density and land cover/use changes.- The central and eastern areas of Tehran, due to the high density of buildings, and the southwestern areas of the city, due to industrial and warehouse land use, have high thermal loads. IntroductionUrban spaces have different and more complex environmental conditions than natural environments because they combine human-made elements and natural features. Today, urban climate specialists focus on a combination of urban and natural factors when zoning urban spaces.The Local Climate Classification (LCZs) is a new and systematic classification system for urban spaces proposed by Stuart and Oke (2012). LCZs classify climates according to the physical structure of the city. Each LCZ is characterized by one or more distinctive features, such as land cover, height, and the distance between trees and buildings.Local Climate Zoning classifies the climate of urban spaces by focusing on the city's physical structure and surface coverage. The LCZ classification has 17 different classes, each of which represents a unique set of characteristics. LCZ classes are individually identified by one or more distinctive characteristics, such as land cover or height, the distance between trees and buildings. Classes 1 to 10 focus more on the physical structure created by humans, while classes A to G focus more on the natural aspect of the city.Theoretical FrameworkThe Local Climate Zoning (LCZ) method was extracted and presented by Stewart and Oke (2012) from the Urban Climate Zones (UCZ) method. This method is presented with an emphasis on land cover characteristics and building density for large cities.In this method, 10 climate zones are specified for urban built spaces and 7 climate zones for natural spaces. The most important data required in this method are Landsat satellite images, which are prepared in both winter and summer seasons to accurately identify the land surface cover. Additionally, for each of the 17 climate classes, it is necessary to take samples in Google Earth to use those samples in the image processing process. Therefore, the accuracy and quality of the map of local climate zones depends on the accuracy of sampling.MethodologyThree types of data were used in this study: meteorological data, satellite images, and spatial information layers.- Meteorological data included temperature, precipitation, wind speed, and wind direction data from the Doshan Tappeh, Geophysical, and Mehrabad meteorological stations in Tehran for the past 20 years.- Satellite images of the city of Tehran were used for two periods: summer and winter.- Spatial information layers included land use data, land cover, and building floors of Tehran.To create a map of the local climate classes in Tehran, the satellite images were converted to a spatial resolution of 100 meters in the SAGA-GIS environment. The measured area was then cut and saved in kml format and added to the Google Earth program. In Google Earth, samples of each climatic class were collected. This stage was the most important and decisive stage of the research, and it was conducted with great accuracy and patience using many samples.Results and DiscussionThe city of Tehran has a diverse range of local climate classes (LCZs) due to its diverse natural and human environments. Tehran is a heterogeneous metropolis in terms of its form and function, and this heterogeneity is reflected in the distribution of LCZs.The results of this study showed that the most common LCZs in Tehran are:- Dense texture and medium height (LCZ 2): These LCZs are characterized by high ambient heat load and poor ventilation capacity. They are generally concentrated in the central and northeastern parts of Tehran.- Dense and short (LCZ 3): These LCZs are also characterized by high ambient heat load and poor ventilation capacity. They are found in other parts of the city, such as the southern and southwestern suburbs.- Low-rise and mid-rise (LCZ 4 to LCZ 6): These LCZs are characterized by lower ambient heat load and better ventilation capacity. They are found in the outer parts of the city, such as the northwestern and southeastern suburbs.- Barren land and agricultural land (LCZ 7 to LCZ 9): These LCZs have the lowest ambient heat load and best ventilation capacity. They are found outside the city limits.The distribution of LCZs in Tehran is affected by a number of factors, including:- The density of buildings- The height of buildings- The presence of vegetation- The topography- The proximity to water bodiesThe high density of buildings in the central and northeastern parts of Tehran is the main reason for the predominance of LCZs 2 and 3 in these areas. The low density of buildings in the outer parts of the city is the main reason for the predominance of LCZs 4 to 6 in these areas. The presence of vegetation helps to reduce the ambient heat load and improve ventilation, while the proximity to water bodies also helps to cool the air.The distribution of LCZs in Tehran has important implications for the city's climate and environment. The high ambient heat load and poor ventilation capacity of LCZs 2 and 3 can contribute to the formation of the urban heat island effect, while the lower ambient heat load and better ventilation capacity of LCZs 4 to 6 can help to mitigate this effect. The presence of vegetation can also help to improve air quality and reduce noise pollution.Overall, the distribution of LCZs in Tehran is a complex issue that is affected by a number of factors. The understanding of this distribution is important for the development of strategies to mitigate the effects of climate change and improve the city's environment.ConclusionThe findings of this study have important implications for the planning and management of Tehran. Identifying areas at risk of high urban heat load and flooding can help to prioritize interventions to reduce these risks. For example, the city could plant more trees and vegetation to cool the air and reduce the urban heat island effect. It could also improve the drainage system to reduce the risk of flooding.Overall, this study provides a valuable contribution to the understanding of the urban climate of Tehran. The findings can be used to develop strategies to improve the livability of the city and reduce the risks of heat stress and flooding.
Urban Ecology
Mostafa Karimi; Samaneh Khosnavaz; Aliakbar Shamsipour; Masoumeh Moghbel
Abstract
Today, urban development and air pollution are the most important issues concerning urban climate that can affect the quality of urban life. Despite the significant progress made in the fuel and engine technology, emission of pollutants in urban environments is still prevalent. As in many other countries, ...
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Today, urban development and air pollution are the most important issues concerning urban climate that can affect the quality of urban life. Despite the significant progress made in the fuel and engine technology, emission of pollutants in urban environments is still prevalent. As in many other countries, the environmental issue is particularly evident in the large cities of Iran such as Tehran, Tabriz, Isfahan, Shiraz, Arak, and Karaj. The rapid urbanization, industrialization, and increasing trend in the use of motor vehicles have caused numerous environmental issues, including the production and distribution of different types of air pollutant, especially in Tehran, the capital. Tehran’s confinement by mountains and meteorological factors such as temperature inversion, the persistence of high-pressure systems with cold air, and local winds exacerbate pollution. Hence, numerous studies have been conducted on air pollution in Tehran. The results have indicated that 73% to 85.5% of the air pollution observed at urban stations is caused by temperature inversions, which are influenced by high pressure and surface radiation. According to the above research, the key factors involved in the spread of pollution over the streets besides the spatial and natural factors that can affect the distribution of air pollutants (i.e. geographic location, topography, etc.) include the arrangement of the buildings, particularly in terms of street width and orientation, distance, and intersections. It should be noted given the significance of the issue that the pollution can have extensive effects although it occurs at the street level, due to the interaction of the dispersal and diffusion of pollutants through meteorological conditions (wind speed and direction and atmospheric stability), the configuration of buildings, and the orientation of streets. Therefore, the main purpose of this research was to specify the characteristics of pollutant flow and dispersion on urban passages in micro scale. For that purpose, the meteorological data, including air temperature, relative humidity, and wind speed and direction, were extracted from Iran Meteorological Organization (IMO) Geophysics Weather Station (the closest station to the area under investigation) for a 20-year statistical period (1991-2010). Two areas (1 and 2) in Municipal District 6 were specified as making up the area under study in this research. Then, the pollutant dispersion data were obtained based on the relationship between traffic volume and pollutant production during two winter and summer months (July and January) and at three times of the day (morning, midday, and afternoon). Finally, the distribution of air pollutants was simulated using the ENVI-met microscale model for building configuration and street orientation in the area under investigation. The results demonstrated that street and pathway orientation plays an important role in the accumulation or distribution of pollutants. Accordingly, the density of pollutants is higher in streets that are perpendicular to the prevailing wind direction. Furthermore, the concentration of pollutants in the main streets of the area under study exhibited a significant relationship with their directions. Pollutant concentration was moderate in streets with prevailing north winds, while the highest and lowest amounts of pollutant concentration were observed in streets with south and southwest winds, respectively. It can be concluded that consideration of the climate conditions in urban design and development (wind speed/direction in particular) can be effective in improvement of air quality in urban areas. Air Pollution, Street Orientation, Wind Speed/Direction, Tehran, ENVI-met Model.
