Urban Ecology
fatemeh ghorbanileylestani,; Hassan sajadzadeh
Abstract
HighlightsComprehensive Analysis: This study investigates the Land Surface Temperature (LST) and Normalized Difference Vegetation Index (NDVI) over two decades (2000-2021) in Karaj, highlighting key trends.Correlation Between Vegetation and Temperature: NDVI shows a strong negative correlation with LST, ...
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HighlightsComprehensive Analysis: This study investigates the Land Surface Temperature (LST) and Normalized Difference Vegetation Index (NDVI) over two decades (2000-2021) in Karaj, highlighting key trends.Correlation Between Vegetation and Temperature: NDVI shows a strong negative correlation with LST, indicating vegetation’s cooling impact.Built-Up Areas vs. Green Spaces: High-density urban areas exhibit elevated temperatures, while regions with dense vegetation are noticeably cooler.Key Findings: The primary drivers behind Karaj’s Urban Heat Island (UHI) effect are the reduction of green spaces and the rise in urban land use. IntroductionWith rapid population growth, urbanization is transforming landscapes, often at the expense of natural green areas. Cities are expanding at unprecedented rates, bringing changes in land use, infrastructure, and building density. Natural permeable surfaces, such as vegetation and open spaces, are replaced by impermeable concrete structures that absorb and retain heat, leading to urban microclimate shifts.This transformation has profound environmental impacts. One of the most concerning consequences is the Urban Heat Island (UHI) effect, where urban areas exhibit higher temperatures compared to their rural counterparts. The UHI effect intensifies as cities grow, impacting energy consumption, air quality, and public health. In this context, reducing UHI has become a priority for sustainable urban planning. Cooling strategies—especially the integration of vegetation—are essential to enhance urban resilience, adapt to climate change, and improve quality of life for city dwellers.Materials and MethodsRemote sensing technology was used in this study as a powerful tool for analyzing urban temperature dynamics and land-use changes. Using Landsat satellite images from 2001 to 2021, we examined LST and NDVI for Karaj. Landsat imagery, with a resolution of 30 meters, was sourced from the USGS database. To ensure consistency, cloud-free images were selected from warm-season months for each year.Data processing involved the extraction of LST and NDVI values for Karaj’s administrative boundaries. The satellite images were preprocessed, and land-use classification was carried out using the maximum likelihood approach, categorizing land into three classes: built-up areas, vegetation, and barren land. This classification provided a foundation for assessing the relationship between LST and vegetation cover.Through correlation and regression tree models, we analyzed the interplay between LST and NDVI. By examining changes in both indices, we aimed to understand vegetation’s role in moderating urban heat in Karaj. Our two main objectives were to (1) assess LST and NDVI variations over time, and (2) explore their interdependencies to determine vegetation's influence on UHI.Discussion of ResultsThe analysis reveals a clear trend of rising temperatures across Karaj over the study period. This temperature increase is strongly associated with urban expansion and the decline of natural vegetation. Our findings highlight that land-use type significantly influences LST, with barren and built-up areas having markedly higher temperatures.Central Karaj, a dense urban area with heavy infrastructure and traffic, recorded the highest surface temperatures. These “hot spots” are concentrated around industrial areas, transportation hubs (airports, metro stations, highways), and zones with minimal vegetation. In contrast, areas with vegetation, such as parks and green belts, exhibited substantially cooler surface temperatures. This difference underscores vegetation’s role in absorbing less heat and promoting natural cooling.The spatial distribution of LST shows the hottest zones in arid lands surrounding the city and densely built-up urban areas. The NDVI data further supports this observation; as NDVI values increase, LST values decline, illustrating a negative correlation between vegetation density and surface temperature. The correlation analysis reveals that regions with higher NDVI values, particularly in the eastern and northeastern parts of Karaj, experienced significantly lower temperatures.The land-use maps demonstrate a significant reduction in barren and vegetated areas, accompanied by an increase in urbanized land. These patterns point to a direct relationship between declining vegetation and rising temperatures, reinforcing the critical need for green spaces in Karaj to mitigate UHI effects. Vegetation, as indicated by NDVI, plays a significant role in temperature regulation, with green areas acting as cooling zones in an increasingly built-up landscape.ConclusionsThis study underscores the pivotal role of vegetation in controlling urban temperatures in Karaj. Through detailed LST and NDVI analyses, the results confirm that vegetation coverage is inversely related to LST, with green spaces helping to mitigate the UHI effect. In contrast, barren lands and dense built-up areas contribute significantly to higher temperatures, highlighting the thermal impact of urban development without adequate vegetation.To address the UHI issue, urban planners and policymakers should prioritize sustainable solutions such as increasing green spaces, incorporating green roofs, and developing urban vegetation initiatives tailored to Karaj’s climate. These approaches not only lower urban temperatures but also enhance the city’s environmental resilience, support biodiversity, and improve the overall quality of urban life.Based on the findings, Karaj’s urban planning efforts should focus on preserving existing vegetation and expanding green infrastructure. Effective land-use policies that integrate vegetation can help counteract the adverse effects of rising temperatures, contributing to a more sustainable and livable urban environment.
Urban Geography
Bahare sadat mousavi; Ata Abdollahi kakroodi; samane Arvandi
Abstract
Highlights- Urban physical expansion has had an impact on spatial and temporal changes in Tasseled cap, including Land Surface Temperature (LST), resulting in an increase in surface temperature.- Surveys conducted in cities have shown that the patterns of urban expansion are influenced by the geographic ...
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Highlights- Urban physical expansion has had an impact on spatial and temporal changes in Tasseled cap, including Land Surface Temperature (LST), resulting in an increase in surface temperature.- Surveys conducted in cities have shown that the patterns of urban expansion are influenced by the geographic setting and regional factors.- The average greenness in areas with wet weather conditions (such as Bandar Anzali and Shirgah) differs from areas with hot and dry weather conditions (such as Kashan), based on climatic conditions.IntroductionGlobally, the physical growth of cities is recognized as a major threat to natural and ecological resources, with a variety of effects including land use change, increased pollution, increased earth surface temperatures, and climate change in both urban and non-urban areas. Planning to minimize the negative environmental effects of urban growth can be aided by quantifying and monitoring the changes caused by urban development in the Tasseled cap of the surface. Urban management and planning can also be derived from the quantitative and qualitative effects of climatic conditions on the type and amount of changes in the Tasseled cap of the surface due to physical expansion of the cities. Furthermore, weather conditions are the primary and effective factor on the type and amount of changes in the Tasseled cap properties of the surface. Considering field measurement is a time-consuming and expensive technique, remote sensing technology will be helpful and effective to overcome this challenge because of its large and continuous coverage, immediate access, and availability of data at various local, regional, and global scales.Theoretical FrameworkUrbanization leads to an increase in land surface temperature (LST). In general, at the patch scale, the more compact the urban growth, the more easily the surface warmed. In most temperature zones, it was found that edge expansion and infilling had significant and favorable correlations with LST. Positive correlations were found in the warm temperature and plateau climatic zones, while negative correlations were seen in the subtropical and intermediate temperature zones, indicating that the influence of outliers on LST had opposite effects in these regions. The findings also demonstrated that LST was significantly influenced in diverse ways by patch area, industrial firm density, population density, and road density. This study further verified the existence of a scale effect; moreover, the results of patch-scale research based on the microscopic perspective were deemed to be more accurate. Overall, understanding the quantitative relationships between UGP and LST is helpful for assessing the complexity of urban climates and for providing a scientific basis for planners and urban managers to optimize urban layouts, (Rao et al., 2021: 105314).MethodologyThe physical development of cities and their impact on the surface's Tasseled cap have been the subject of numerous studies. This research was conducted with the aim of investigating the effect of different climatic conditions on the changes in Tasseled cap by using remote sensing. The cities of Kashan, Bandar Anzali, and Sirjan were chosen as the study regions for this research because of their diversity in geographical features, climatic features, and land cover. So, between 1991 and 2021, the effects of various climatic conditions and changes in thermal temperature on these cities were examined. For this purpose, satellite images of Landsat 5 TM sensor and Landsat 8 OLI sensor used.ConclusionThis study investigated the effect of climatic conditions on the spatial and temporal changes in Tasseled cap, including LST, in three cities in Iran: Kashan, Sirjan, and Bandar Anzali. The results showed that urban expansion has led to an increase in LST in all three cities. However, the increase in LST was more pronounced in Kashan, which has a hot and dry climate, than in Sirjan and Bandar Anzali, which have more humid climates. This is because the reduction of vegetation cover in urban areas reduces evaporation and transpiration, which leads to an increase in surface temperature.The study also found that the changes in other Tasseled cap indices, such as brightness and wetness, were also affected by climatic conditions. In the humid cities of Bandar Anzali and Sirjan, the increase in LST was accompanied by an increase in brightness and wetness. This is because the presence of vegetation helps to reflect sunlight and retain moisture, which helps to cool the surface. In contrast, in the hot and dry city of Kashan, the increase in LST was accompanied by a decrease in brightness and wetness.The findings of this study suggest that the planning and management of urban areas should take into account the local climatic conditions. In hot and dry climates, it is important to preserve vegetation cover to help reduce surface temperatures. In humid climates, it is important to design urban spaces in a way that maximizes the benefits of vegetation, such as shading and moisture retention.The study also suggests that future studies should consider the effects of climatic conditions on the changes in Tasseled cap in different cities. This will help to improve our understanding of the relationship between urban development and climate change.
