scholarly journals Effect of Land Cover Fractions on Changes in Surface Urban Heat Islands Using Landsat Time-Series Images

2019 ◽  
Vol 16 (6) ◽  
pp. 971 ◽  
Author(s):  
Tao Chen ◽  
Anchang Sun ◽  
Ruiqing Niu
Keyword(s):  
Land Cover ◽  
Urban Heat Island ◽  
Land Surface ◽  
Urban Heat Islands ◽  
Urban Heat Island Intensity ◽  
Heat Island ◽  
Impervious Surfaces ◽  
Heat Islands ◽  
Urban Heat ◽  
Surface Urban Heat Island

Man-made materials now cover a dominant proportion of urban areas, and such conditions not only change the absorption of solar radiation, but also the allocation of the solar radiation and cause the surface urban heat island effect, which is considered a serious problem associated with the deterioration of urban environments. Although numerous studies have been performed on surface urban heat islands, only a few have focused on the effect of land cover changes on surface urban heat islands over a long time period. Using six Landsat image scenes of the Metropolitan Development Area of Wuhan, our experiment (1) applied a mapping method for normalized land surface temperatures with three land cover fractions, which were impervious surfaces, non-chlorophyllous vegetation and soil and vegetation fractions, and (2) performed a fitting analysis of fierce change areas in the surface urban heat island intensity based on a time trajectory. Thematic thermal maps were drawn to analyze the distribution of and variations in the surface urban heat island in the study area. A Multiple Endmember Spectral Mixture Analysis was used to extract the land cover fraction information. Then, six ternary triangle contour graphics were drawn based on the land surface temperature and land cover fraction information. A time trajectory was created to summarize the changing characteristics of the surface urban heat island intensity. A fitting analysis was conducted for areas showing fierce changes in the urban heat intensity. Our results revealed that impervious surfaces had the largest impacts on surface urban heat island intensity, followed by the non-chlorophyllous vegetation and soil fraction. Moreover, the results indicated that the vegetation fraction can alleviate the occurrence of surface urban heat islands. These results reveal the impact of the land cover fractions on surface urban heat islands. Urban expansion generates impervious artificial objects that replace pervious natural objects, which causes an increase in land surface temperature and results in a surface urban heat island.

scholarly journals Spatiotemporal Variation of Surface Urban Heat Islands in Relation to Land Cover Composition and Configuration: A Multi-Scale Case Study of Xi’an, China

2020 ◽  
Vol 12 (17) ◽  
pp. 2713 ◽  
Author(s):  
Linlin Lu ◽  
Qihao Weng ◽  
Da Xiao ◽  
Huadong Guo ◽  
Qingting Li ◽  
...  
Keyword(s):  
Land Cover ◽  
Land Surface ◽  
Green Space ◽  
Grid Cell ◽  
Urban Heat Islands ◽  
Heat Island ◽  
Heat Islands ◽  
Multi Scale ◽  
Urban Heat ◽  
Surface Urban Heat Island

Urban heat islands (UHI) can lead to multiple adverse impacts, including increased air pollution, morbidity, and energy consumption. The association between UHI effects and land cover characteristics has been extensively studied but is insufficiently understood in inland cities due to their unique urban environments. This study sought to investigate the spatiotemporal variations of the thermal environment and their relationships with land cover composition and configuration in Xi’an, the largest city in northwestern China. Land cover maps were classified and land surface temperature (LST) was estimated using Landsat imagery in six time periods from 1995 to 2020. The variations of surface heat island were captured using multi-temporal LST data and a surface urban heat island intensity (SUHII) indicator. The relationship between land cover features and land surface temperature was analyzed through multi-resolution grids and correlation analysis. The results showed that mean SUHII in the study area increased from 0.683 °C in 1995 to 2.759 °C in 2020. The densities of impervious surfaces had a stronger impact on LST than green space, with Pearson’s correlation coefficient r ranging from 0.59 to 0.97. The correlation between normalized difference impervious surface index and LST was enhanced with the enlargement of the grid cell size. The correlations between normalized difference vegetation index and LST reached maxima and stabilized at grid cell sizes of 210 and 240 m. Increasing the total area and aggregation level of urban green space alleviated the negative impacts of UHI in the study area. Our results also highlight the necessity of multi-scale analysis for examining the relationships between landscape configuration metrics and LST. These findings improved our understanding of the spatiotemporal variation of the surface urban heat island effect and its relationship with land cover features in a major inland city of China.

Bi-temporal Monitoring the Spatial Pattern and Variations of the Surface Urban Heat Island in three Chinese Coastal Megacities: A Comparative Study of Guangzhou, Hangzhou, and Shanghai.

2020 ◽  
Author(s):  
Fei Liu
Keyword(s):  
Land Cover ◽  
Urban Heat Island ◽  
Hot Spots ◽  
Land Surface ◽  
Urban Expansion ◽  
Spatial Regression ◽  
Heat Island ◽  
Thermal Environments ◽  
Urban Heat ◽  
Surface Urban Heat Island

<p>The side-effect of booming urbanization on the ecosystem and climate system has been continuously exacerbating. The coastal metropolises are located at the interface between land and ocean, unavoidably influenced by multiple aspects of the terrestrial environments, aquatic ecosystems, and urban developments. Thus, the environmental health of coastal metropolis should be more concerned. In this study, targeting Guangzhou, Hangzhou, and Shanghai, an attempt was made to evaluate the spatiotemporal patterns and variations of surface urban heat island (SUHI) in three coastal metropolises of China based on Landsat-derived land surface temperatures (LST) and land cover data. The results indicate that overall, within a nearly 15-year interval, the extents of hot spots in three metropolises were significantly expanded, the spatial patterns of SUHI have been transformed from monocentric to polycentric high-LST clusters, which were identical to the trend of urban expansion. However,  these three metropolises possess distinct features in terms of the thermal layouts and land cover/use composition. Although the total area of SUHI hot spots in Shanghai has surged, the intensity of some hot spots has been a shrink. Besides, the interactions and associations between SUHI and urban development were investigated using spatial regression analysis. The urban composition and configuration considerably affected the intensity of SUHI. Terrain morphology constrained the SUHI. Prolific population growth had a continuing effect on SUHI formation. The proportion of forests displayed a consistently critical influence on easing the adverse of SUHI. Additionally, it is essential to appropriately consider the impacts of water in the comparative analysis of different thermal environments. However, water might be treated as a time-invariant factor and have a limited effect on the bi-temporal comparison for each metropolis. These findings suggest the policy-makers and urban planners should balance and optimize the land cover/use configurations with accommodating the increasing population, reasonably maximize the reservations of the greenbelt and green space under improving the utilization of urban infrastructures and constructions.</p>

scholarly journals Surface Urban Heat Island Assessment of a Cold Desert City: A Case Study over the Isfahan Metropolitan Area of Iran

Atmosphere ◽  
2021 ◽  
Vol 12 (10) ◽  
pp. 1368
Author(s):  
Alireza Karimi ◽  
Pir Mohammad ◽  
Sadaf Gachkar ◽  
Darya Gachkar ◽  
Antonio García-Martínez ◽  
...  
Keyword(s):  
Urban Heat Island ◽  
Metropolitan Area ◽  
Negative Correlation ◽  
Land Surface ◽  
Vegetation Index ◽  
Urban Heat Islands ◽  
Heat Island ◽  
Cold Desert ◽  
Urban Heat ◽  
Surface Urban Heat Island

This study investigates the diurnal, seasonal, monthly and temporal variation of land surface temperature (LST) and surface urban heat island intensity (SUHII) over the Isfahan metropolitan area, Iran, during 2003–2019 using MODIS data. It also examines the driving factors of SUHII like cropland, built-up areas (BI), the urban–rural difference in enhanced vegetation index (ΔEVI), evapotranspiration (ΔET), and white sky albedo (ΔWSA). The results reveal the presence of urban cool islands during the daytime and urban heat islands at night. The maximum SUHII was observed at 22:30 pm, while the minimum was at 10:30 am. The summer months (June to September) show higher SUHII compared to the winter months (February to May). The daytime SUHII demonstrates a robust positive correlation with cropland and ΔWSA, and a negative correlation with ΔET, ΔEVI, and BI. The nighttime SUHII displays a negative correlation with ΔET and ΔEVI.

scholarly journals Identification of Urban Heat Islands &Its Relationship withVegetation Cover: A Case Study of Colombo & Gampaha Districts in Sri Lanka

2019 ◽  
Vol 8 (2) ◽  
Author(s):  
G.M.T.S. Fernando
Keyword(s):  
High Temperature ◽  
Surface Temperature ◽  
Urban Heat Island ◽  
Land Surface Temperature ◽  
Vegetation Cover ◽  
Land Surface ◽  
Urban Heat Islands ◽  
Heat Island ◽  
Heat Islands ◽  
Urban Heat

Global Warming is a major environmental problem that all kind of organisms has been affected at present. Urban Heat Island (UHI) is one of primary impacts of Global Warming. UHI is a phenomenon that the temperature of urban area is higher than surrounding rural areas or suburban areas. This increasing trend of temperature in urban areas affects many environmental entities such as air quality, water resources, habitats behaviors and climate changes. The most remarkable incident that relate with UHI is the difference of thermal properties of the surfaces. Many countries experience the consequences of Urban Heat Islands in many aspects such as economic, health, social and environmental affects. Thus to mitigate such impacts of UHI, it is very important to identify the main reasons behind this. In this paper UHIs in Colombo, Gampaha Districts and the relationship between UHI and vegetation cover were analyzed based on Landsat 8, 30m resolution data. Land Surface Temperature was derived from Landsat thermal Infrared band through several equations of United State Geological Survay (USGS) guidelines using Arc GIS 10. Conversion of Digital Number (DN) values to Top of Atmosphere (TOA) Radiance, Conversion of TOA Radiance to Satellite Brightness temperature and final calculation of Land Surface Temperature considering land surface emissivity are the steps that had been done for the analysis. Vegetation cover was derived by using vegetation index with the Red and Near Infra Red bands. The result shows that the land high surface temperature directly relates with the urbanized regions where vegetation cover is very less. High temperature difference could be identified that cause to arise the urban heat island effects in Colombo & Gampaha districts. There is a strong linearly negative correlation with correlation coefficient value of -0.742 between land surface temperature and vegetation cover. 78.8 km2 (including water) of total area had been identified as NDVI value less than 0.1. And extent of high temperature area was 74.12 km2 where temperature more than 27oC at 10.22am. The area in temperature range of 25-27 was 464.95km2 and area in NDVI value range 0.1-0.2 was 333.04 km2. 1471.1 km2 was identified as NDVI value between 0.3-0.4 and the area at low temperature was 1529 km2where temperature less than 25oC. According to this results, high temperature at non-vegetated areas and low temperature at vegetated areas could be noted very clearly. This is probably due to the ecological function of vegetation that lay down the surface temperature from high evapotranspiration. Vegetated areas are mostly sensed with surface temperature.Thus research output can be useful for policy-makers and planners of development projects such as Western province Megapolis project as well as for general public to understand the urban heat island effects and importance of vegetation cover to mitigate such impacts.

scholarly journals Monitoring the Detailed Dynamics of Regional Thermal Environment in a Developing Urban Agglomeration

Sensors ◽  
2020 ◽  
Vol 20 (4) ◽  
pp. 1197 ◽  
Author(s):  
Yue Liu ◽  
Hui Li ◽  
Peng Gao ◽  
Cheng Zhong
Keyword(s):  
Urban Heat Island ◽  
Land Surface ◽  
Temporal Dynamics ◽  
Thermal Environment ◽  
Urban Heat Islands ◽  
Heat Island ◽  
Heat Islands ◽  
Inner Cities ◽  
Urban Heat ◽  
Moderate Resolution Imaging Spectroradiometer

Many studies have revealed the characteristics and spatial-temporal dynamics of the thermal environment in specific cities or urban agglomerations (UA), as well as the associated determining factors. However, few studies focus on the changing relationships (the difference, distance, interaction, etc.) among inner cities’ heat islands in a UA, which represent not only the detailed dynamics of regional thermal environment (RTE), but also the changing competition and cooperation among cities in a developing UA. In this study, we used Moderate Resolution Imaging Spectroradiometer (MODIS) land surface temperature (LST) products to map and analyze the detailed dynamics of the Beijing-Tianjin-Hebei (BTH) UA thermal environment. From 2001 to 2015, the mean surface urban heat island intensity (SUHII) of the BTH increased significantly, and the surface urban heat islands (SUHIs) in the southern BTH have rapidly increased, expanded and connected, eventually forming a large heat islands agglomeration. According to correlation analysis, urban sprawl probably led to the expansion and enhance of SUHIs in the south plain, while the forest has significantly alleviated urban heat island effect in northern mountains. The results expose the detailed evolution process of BTH thermal environment, and the changing relationships among the inner cities. In a developing UA, mitigation solutions (e.g., ecological corridors or controlling energy consumption) are in demand to stop the formation of a great heat region.

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