Spatiotemporal Characteristics of Urban Surface Temperature and Its Relationship with Landscape Metrics and Vegetation Cover in Rapid Urbanization Region

Global warming has obtained more and more attention because the global mean land surface temperature (LST) has increased since the late 19th century. Urban heat island (UHl) effect and its thermal environment are the most important themes in urban climatology and environment researches. One of the possible causes to UHI effect is the drastic reduction in the green space in cities.The coastal cities of southeast Fujian province is the most economically developed and densely populated areas of Fujian province,even in China,and also it is experiencing rapid urbanlization that has resulted in remarkable UHI effect,which will be sure to inference the regional and urban climate,environment,and socio-ecomomic development. In this study, MODIS data of July to August acquired from 2001 to 2007 in coastal cities of southeast Fujian province were elaborately selected out to retrieve the metrics of,land surface tempertuare,normalized difference vegetation index (NDVI) and albedo so as to investigate the intensity, the spatial-temporal pattern, the tendency of UHI effect,monitor annual changes and evaluate the UHI effect though urban radio index (URI) over the study period. Additionally, a new methodology and analysis techniques what was called Urban Thermal Environment Information TuPu (UTEITP) was introduced to detect and measure within-class changes of LST from the spatial, temporal and processes view,try to find the conversion mechanism and analyze the relationship between LST,albedo and NDVI qualitatively. Morever,a correlation model was built to quantitatively analyze and better understanding the relationships between LST and NDVI,LST and albedo.The results showed that UHI effect was keeping on strengthening during the whole study period with a increase tendency overall.UTEITP provided a systematic and effective way to derive comparable changes and processes.Our analysis based on UTEITP and correlation model indicates that there was a linear relationship among surface temperature,NDVI and albedo for all study years, whereas the relationship between LST and NDVI was negative,but positive correlation was shown between NDVI and albedo.These result evidence reminds us to take some instructive measures to weaken the effect of urban heat island,improve the city's thermal and habitat environment and urban sustainable development.

The urban planner´s role should be adapted to the current globalised and overspecialised economic and environmental context, envisioning a balance at the regional scale, apprehending not only new technologies, but also new mapping principles, that allow obtaining multidisciplinary integral overviews since the preliminary stages of the design process. The urban heat Island (UHI) is one of the main phenomena affecting the urban climate. In the Netherlands, during the heat wave of 2006, more than 1,000 extra deaths were registered. UHI-related parameters are an example of new elements that should be taken into consideration since the early phases of the design process.\n
\nProblem statement
\n\nThus, the development of urban design guidelines to reduce the heat islands in Dutch cities and regions requires first an overall reflection on the heat island phenomenom (relevance of the large scale assessment, existing tools, instruments) and proposal of integrative and catalysing mapping strategies and then a specific assessment of the phenomenom at the selected locations in The Netherlands (testing those principles).\n
\nMain research question
\n\nCould the use of satellite imagery help analyse the UHI in the Netherlands and contribute to suggest catalysing mitigation acions actions implementable in the existing urban context of the cities, regions and provinces assessed?\n
\nMethod
\n\nThe development of urban design principles that aim at reaching a physical balance at the regional scale is critical to ensure a reduction of the UHI effect. Landsat and Modis satellite imagery can be analysed and processed using ATCOR 2/3, ENVI 4.7 and GIS, allowing not only a neighbourhood, city and regional scale assessment, but also generating holistic catalysing mapping typologies: game-board, rhizome, layering and drift, which are critical to ensure the integration of all parameters. The scientific inputs need to be combined not only with other disciplines but often also with existing urban plans. The connection between scientific research and existing agreed visions is critical to ensure the integration of new aspects into the plans.\n
\nResults
\n\nAt the neighbourhood level the areas that have a greater heat concentration in the cities of Delft, Leiden, Gouda, Utrecht and Den Bosch are the city centres characterised by their red ceramic roof tiles, brick street paving, and canals. Several mitigation strategies could be implemented to improve the UHI effect in those areas; however, since the city centres are consolidated and listed urban areas, the mitigation measures that would be easier to implement would consist in improving the roof albedo. A consistent implementation of albedo improvement measures (improving the thermal behaviour not only of flat roofs, but also of tiled pitched roofs) of all roofs included in the identified hotspots (with an average storage heat flux greater than 90 W/m2) would help reduce the temperatures between 1.4°C and 3°C. Pre-war and post-war compact and ground-based neighbourhoods present similar thermal behaviour of the surface cover, and green neighbourhoods and small urban centres also present similar thermal behaviour.\n
\n\nAt the city scale the analysis of 21 medium-size cities in the province of North Brabant, which belongs to the South region of the county -in relative terms the most affected by the UHI phenomenon during the heat wave of 2006-, reveals that albedo and normalised difference vegetation index (NDVI) are the most relevant parameters influencing the average nightime land surface temperature (LST). Thus, imperviousness, distance to the nearest town and the area of the cities do not seem to play a significant role in the LST night values for the medium-size cities analysed in the region of North Brabant, which do not exceed 7,700 ha in any case. The future growth of most medium-size cities of the regions will not per se aggravate the UHI phenomenon; in turn it will be the design of the new neighbourhoods that will impact the formation of urban heat in the province.\n
\n\nThe average day LST of provincial parks in South Holland varies depending on the land use. The analysis of the average night LST varies depending of the land use of the patches. The following surfaces are arranged from the lowest to the highest temperatures: water surfaces, forests, cropland, and greenhouse areas. For each of these land uses, NDVI, imperviousness and landscape shape index (LSI) shape index influence the thermal behaviour of the patches differently. NDVI is inversely correlated to day LST for all categories, imperviousness is correlated to day LST for all areas which do not comprise a significant presence of greenhouses (grassland and built patches) and inversely correlated to LST for areas with a high presence of greenhouses (cropland and warehouses). Greenhouse surfaces have highly reflective roofs, which contribute to the reduction of day LST. Finally, landscape shape index varies depending on the nature of the surrounding patches, especially for small patches (built areas, forests and greenhouse areas). When the patches analysed are surrounded by warmer land uses, slender and scattered patches are warmer, more compact and large ones are cooler. In turn, when they are surrounded by cooler patches it is the opposite: slenderer and scattered patches are cooler and more compact and larger ones are warmer. In Midden-Delfland (1 of the 6 South Holland provincial parks), most of the hotspots surrounding the park are adjacent to grassland patches. The measure to increase the cooling capacity of those patches would consist in a change of land use and/or an increase of NDVI of the existing grassland patches.\n
\nConclusions
\n\nSatellite imagery can be used not only to analyse the heat island phenomenom in Dutch neighbourhoods, cities and regions (identify neighbourhoods with highest surface temperature, identify impact of city size and morphology in surface temperature, calcuate average surface temperature for different land uses…), but also to suggest mitigation actions for the areas assessed. Moreover, satellite imagery is here used to generate catalysing mapping typologies: game-board, rhizome, layering and drift, ensuring that the measures proposed remain accurate enough to actualy be efficient and open enough to be compatible with the rest of urban planning priorities.

Impacts of landscape structure on surface urban heat islands: A case study of Shanghai, China

The Urban Heat Island (UHI) effect has been extensively studied as a global issue. The urbanization process has been proved to be the main reason for this phenomenon. Over the past 20 years, the built-up area of Zhengzhou city has grown five times larger, and the UHI effect has become increasingly pressing for the city’s inhabitants. Therefore, mitigating the UHI effect is an important research focus of the expanding capital city of the Henan province. In this study, the Landsat 8 image of July 2019 was selected from Landsat collection to obtain Land Surface Temperature (LST) by using Radiative Transfer Equation (RTE) method, and present land cover information by using spectral indices. Additionally, high-resolution Google Earth images were used to select 123 parks, grouped in five categories, to explore the impact factors on park cooling effect. Park Cooling Intensity (PCI) has been chosen as an indicator of the park cooling effect which will quantify its relation to park patch metrics. The results show that: (1) Among the five studied park types, the theme park category has the largest cooling effect while the linear park category has the lowest cooling effect; (2) The mean park LST and PCI of the samples are positively correlated with the Fractional Vegetation Cover (FVC) and with Normalized Difference Water Index (NDWI), but these are negatively correlated with the Normalized Difference Impervious Surface Index (NDISI). We can suppose that the increase of vegetation cover rate within water areas as well as the decrease of impervious surface in landscape planning and design will make future parks colder. (3) There is a correlation between the PCI and the park characteristics. The UHI effect could be mitigated by increasing of park size and reducing park fractal dimension (Frac_Dim) and perimeter-area ratio (Patario). (4) The PCI is influenced by the park itself and its surrounding area. These results will provide an important reference for future urban planning and urban park design to mitigate the urban heat island effect.

Increase in land surface temperature (LST) of growing urban areas in the current global warming scenario is a cause of concern for city planners. This study discusses the impact of land-use/land-cover (LULC) change on LST of the area in and around Rajarhat block, North 24-Parganas District, West Bengal, covering an area of 165 km2. Multi-spectral and multi-temporal satellite data from Landsat 5 TM (1990), Landsat 8 OLI (2016) and Sentinel 2A (2016) are used for the LULC mapping, and thermal infrared data from Landsat 5 TM and Landsat 8 TIRS (2016) are used for estimating the LST of 1990 and 2016. Results show that land-use pattern in November has changed in Rajarhat from 1990 to 2016: 13 km2 of vegetation cover lost due to urbanization; 9.3 km2 of open land converted to agricultural land and open fields/parks; 1.4 km2 of aquaculture ponds converted to tree cover/scrublands and 1.45 km2 of lakes/ponds filled up. Loss of vegetation (scrubland and tree) cover resulted in LST rise by about 1.5 °C. Aquaculture ponds have the ability to resist the rise in LST since the increase in temperature of this class is only 0.24 °C due to increase in its area. This change in land-use pattern over 26 years has increased the LST by 0.94 °C. The urban-heat-island (UHI) phenomenon has also increased. The area of the ‘strongest’ heat-island phenomenon, as per UTVFI classification scheme, has increased by 20.1 km2. Positive correlation is observed between NDBI and LST’s of urban areas (r = 0.002 for 1990 and r = 0.047 for 2016) which suggests that urbanization is responsible for the rise in LST. The NCEP NOAA surface temperature model suggests that the long-term trends in the rise in maximum LST over Rajarhat is about 1 °C from January 1990 to November 2016 with 90% confidence level validating the extracted LST data from satellites. Sustainable urban planning is required to arrest the rise in LST which includes urban forestry, construction of water bodies and fountains, preserving existing aquaculture ponds and reducing construction activities.

The effect of the expansion of urban impervious surfaces on surface urban heat islands (UHIs) has attracted research attention due to its relevance for studies of local climatic change and habitat comfort. In this study, using five satellite images of Xiamen city, Southeast China (four images from the Landsat 5 Thematic Mapper (TM) and one from the Landsat 8 Operational Land Imager/Thermal Infrared Sensor (OLI/TIRS)) acquired in summer between 1989 and 2016, together with spatial statistical methods, the changes in impervious surface area (ISA) were investigated, the spatiotemporal variation of the intensity of urban heat islands (UHIs) was explored, and the relationships between land surface temperature (LST) and the percentage of impervious surface area (ISA%), the normalized difference vegetation index (NDVI), and fractional vegetation coverage (Fv) were investigated. The results showed the following: (1) According to the biophysical composition index (BCI) combined with an ISA post-processing method, Xiamen has witnessed a substantial increase in ISA, showing a 6.1-fold increase from 1989 to 2016. The direction of ISA expansion was consistent throughout the study period in each of the five districts of Xiamen; (2) a bay-like UHI form is observed in the study area, which is remarkably distinct from the central-radial UHI form observed in previous studies of other cities; (3) the extent of UHIs in Xiamen greatly increased between 1989 and 2016, experiencing a 4.7-fold increase in UHI areas during this time. However, during the same period, the urban heat island ratio index (URI)—that is, the ratio of UHI area to ISA—decreased slightly. The UHI area decreased in some urban parts of Xiamen due to a significant increase in vegetation coverage, urban village redevelopment, and the construction of new parks; (4) sea ports and heavy industrial zones are the greatest contributor to surface UHI, followed by urban villages; and (5) LST is strongly positively correlated with ISA%. Each 10% increase in ISA was associated with an increase in summer LST of 0.41 to 0.91 K, which compares well with the results of related studies. This study presents valuable information for the development of regional urban planning strategies to mitigate the effects of UHIs during rapid urbanization.

Assessing the effects of land use spatial structure on urban heat islands using HJ-1B remote sensing imagery in Wuhan, China

Undoubtedly, urbanization has improved human living conditions. However, it has also altered the natural landscape, leading to negative consequences such as increased Land Surface Temperature (LST) and Urban Heat Island (UHI) due to the expansion of Impervious Surface (IS). Much research has been conducted in other countries on the effects of changing urban landscape structures on LST and UHI formation. However, in Sri Lanka, only a few studies have been available on this topic, primarily concentrating on major cities like Colombo. Impervious Surface is absorbing high amounts of solar energy as well, which accelerates the magnitude of UHI in urbanized areas. Remote Sensing indices such as the Normalized Difference Vegetation Index (NDVI), Normalized Difference Buildup Index (NDBI), UHI, and Environmental Criticality Index (ECI) can effectively be used to quantify the intensity of the UHI phenomenon. This study aimed to investigate the effect of spatiotemporal variations in IS and Green Surface (GS) on UHI, LST, and the environmental criticality in Galle Municipal Council (MC), Sri Lanka employing multi-temporal Landsat-5 and 8 data from four different periods: 1996, 2005, 2014, and 2022. Different geospatial techniques including supervised image classification, Urban-Rural Gradient Zone (URGZ) analysis, grid-based analysis, UHI profiles, and regression analysis were used in the study. The findings revealed that Impervious Surface increased by 42.3% (7.34 km2) while Green Surface had a decline of 22.5% (3.91 km2) during the concerned period. This landscape transition led to a 2.74 C increase in mean surface temperature in the study area, along with a 9.5 C increase in the UHI index during 26 years. The results further revealed that Impervious Surface rapidly developed within 4 km (URGZ1-19) from city center, while Green Surface decreased. Newly built-up areas within the 1.5 km gradient (URGZ1-URGZ8) were more affected by increased LST. A positive correlation was identified between NDBI and LST, especially in the year 2022, with an R2 of 0.457, while NDVI and LST reported a negative R2 of 0.257. The grid-based analysis demonstrated an increasingly positive relationship between mean LST and the fraction of Impervious Surface, highlighting the role of built-up areas in raising LST and UHI in the MC. As a result, very high environmental critical areas have been concentrated in and around high-density Impervious Surface. Thus, it can be predicted that the UHI effect and Environmental Criticality (EC) may increase further in the future. In this context, planning agencies should prioritize green urban planning strategies, such as implementing green belts and urban agriculture in the study area, particularly in and around areas with high LST and high environmental criticality. This approach may help protect the natural environment and sustainably ensure the health of the urban community.

Globally, the urban heat island (UHI) effect is a major problem which leads to urban residents suffering from adverse urban ecological environments and serious health risks. Understanding the impacts of urban landscape features on the thermal environment has been an important focus across various fields of research. The purpose of this study is to analyze the impacts of urban heat source–sink landscape patterns on urban heat islands, using the fast-growing Zhengzhou City in central China as the case study. Landsat data (captured in 1996, 2006, and 2014), various geospatial approaches, and correlation analysis were applied to facilitate the analysis. Based on the contributions of the urban landscape to land surface temperature (LST), we empirically identified the heat sources and heat sinks. Then, the composition and configurations of heat source and sink landscapes were estimated by a series of spatial metrics at the landscape and class levels. The results showed that the overall mean land surface temperature (LST) in the study area increased by 2.72 °C from 1996 to 2014. This observed increasing trend in overall mean LST is consistent with the process of rapid urbanization in the study area, which was evidenced by the dramatic increase in impervious surfaces and the substantial loss in vegetation cover. Generally, as observed, landscape composition has a stronger influence on LST than does landscape configuration. For heat sources, the proportion, size, aggregation, and density of patches have positive effects on LST, while adjusting the spatial distribution and abundance of urban landscape are effective ways to control the UHI effects. In contrast, the percentage, size, density, and aggregation of heat sink patches have negative effects on LST. Additionally, the effects of increasing total patch edges and shape complexity should be considered when mitigating the UHI effect. These findings are beneficial for furthering our understanding of how urban landscape patterns affect UHI, and they can help optimize urban landscape patterns to alleviate the UHI effect and enhance sustainable development in the study area.

Examining the nexus between land surface temperature and urban growth in Chattogram Metropolitan Area of Bangladesh using long term Landsat series data

Urban and regional heat island adaptation measures in the Netherlands

The urban planner´s role should be adapted to the current globalised and overspecialised economic and environmental context, envisioning a balance at the regional scale, apprehending not only new technologies, but also new mapping principles, that allow obtaining multidisciplinary integral overviews since the preliminary stages of the design process. The urban heat Island (UHI) is one of the main phenomena affecting the urban climate. In the Netherlands, during the heat wave of 2006, more than 1,000 extra deaths were registered. UHI-related parameters are an example of new elements that should be taken into consideration since the early phases of the design process. Problem statement Thus, the development of urban design guidelines to reduce the heat islands in Dutch cities and regions requires first an overall reflection on the heat island phenomenom (relevance of the large scale assessment, existing tools, instruments) and proposal of integrative and catalysing mapping strategies and then a specific assessment of the phenomenom at the selected locations in The Netherlands (testing those principles). Main research question Could the use of satellite imagery help analyse the UHI in the Netherlands and contribute to suggest catalysing mitigation acions actions implementable in the existing urban context of the cities, regions and provinces assessed? Method The development of urban design principles that aim at reaching a physical balance at the regional scale is critical to ensure a reduction of the UHI effect. Landsat and Modis satellite imagery can be analysed and processed using ATCOR 2/3, ENVI 4.7 and GIS, allowing not only a neighbourhood, city and regional scale assessment, but also generating holistic catalysing mapping typologies: game-board, rhizome, layering and drift, which are critical to ensure the integration of all parameters. The scientific inputs need to be combined not only with other disciplines but often also with existing urban plans. The connection between scientific research and existing agreed visions is critical to ensure the integration of new aspects into the plans. Results At the neighbourhood level the areas that have a greater heat concentration in the cities of Delft, Leiden, Gouda, Utrecht and Den Bosch are the city centres characterised by their red ceramic roof tiles, brick street paving, and canals. Several mitigation strategies could be implemented to improve the UHI effect in those areas; however, since the city centres are consolidated and listed urban areas, the mitigation measures that would be easier to implement would consist in improving the roof albedo. A consistent implementation of albedo improvement measures (improving the thermal behaviour not only of flat roofs, but also of tiled pitched roofs) of all roofs included in the identified hotspots (with an average storage heat flux greater than 90 W/m2) would help reduce the temperatures between 1.4°C and 3°C. Pre-war and post-war compact and ground-based neighbourhoods present similar thermal behaviour of the surface cover, and green neighbourhoods and small urban centres also present similar thermal behaviour. At the city scale the analysis of 21 medium-size cities in the province of North Brabant, which belongs to the South region of the county -in relative terms the most affected by the UHI phenomenon during the heat wave of 2006-, reveals that albedo and normalised difference vegetation index (NDVI) are the most relevant parameters influencing the average nightime land surface temperature (LST). Thus, imperviousness, distance to the nearest town and the area of the cities do not seem to play a significant role in the LST night values for the medium-size cities analysed in the region of North Brabant, which do not exceed 7,700 ha in any case. The future growth of most medium-size cities of the regions will not per se aggravate the UHI phenomenon; in turn it will be the design of the new neighbourhoods that will impact the formation of urban heat in the province. The average day LST of provincial parks in South Holland varies depending on the land use. The analysis of the average night LST varies depending of the land use of the patches. The following surfaces are arranged from the lowest to the highest temperatures: water surfaces, forests, cropland, and greenhouse areas. For each of these land uses, NDVI, imperviousness and landscape shape index (LSI) shape index influence the thermal behaviour of the patches differently. NDVI is inversely correlated to day LST for all categories, imperviousness is correlated to day LST for all areas which do not comprise a significant presence of greenhouses (grassland and built patches) and inversely correlated to LST for areas with a high presence of greenhouses (cropland and warehouses). Greenhouse surfaces have highly reflective roofs, which contribute to the reduction of day LST. Finally, landscape shape index varies depending on the nature of the surrounding patches, especially for small patches (built areas, forests and greenhouse areas). When the patches analysed are surrounded by warmer land uses, slender and scattered patches are warmer, more compact and large ones are cooler. In turn, when they are surrounded by cooler patches it is the opposite: slenderer and scattered patches are cooler and more compact and larger ones are warmer. In Midden-Delfland (1 of the 6 South Holland provincial parks), most of the hotspots surrounding the park are adjacent to grassland patches. The measure to increase the cooling capacity of those patches would consist in a change of land use and/or an increase of NDVI of the existing grassland patches. Conclusions Satellite imagery can be used not only to analyse the heat island phenomenom in Dutch neighbourhoods, cities and regions (identify neighbourhoods with highest surface temperature, identify impact of city size and morphology in surface temperature, calcuate average surface temperature for different land uses…), but also to suggest mitigation actions for the areas assessed. Moreover, satellite imagery is here used to generate catalysing mapping typologies: game-board, rhizome, layering and drift, ensuring that the measures proposed remain accurate enough to actualy be efficient and open enough to be compatible with the rest of urban planning priorities.

Kayseri, a densely urbanized province in Türkiye, grapples with pressing challenges of air pollution and limited green spaces, accentuating the need for strategic urban planning. This study, utilizing Landsat 8 and Landsat 9 satellite imagery, investigates the evolution of land surface temperatures (LST) and urban heat island (UHI) effects in key districts—Kocasinan, Melikgazi, Talas, and Hacılar—between 2013 and 2022. This research has been complemented with an analysis of the Normalized Difference Vegetation Index (NDVI) and the Normalized Difference Built-Up Index (NDBI), exploring correlations among the LST, UHI, NDVI, and NDBI changes. The findings indicate that a significant portion (65% and 88%) of the study area remained unchanged with respect to the NDVI and NDBI differences. This research’s findings reveal that a substantial portion (65% and 88%) of the study area exhibited consistency in the NDVI and NDBI. Noteworthy increases in the NDVI were observed in 20% of the region, while only 4% exhibited higher NDBI. Strikingly, the UHI displayed strong negative correlations with the NDVI and robust positive correlations with the NDBI. The LST changes demonstrated a reduced temperature range, from 21 to 51 °C in 2013, to 18 to 40 °C in 2022. Localized environmental factors, notably at the National Garden site, showcased the most significant temperature variations. Notably, the UHI exhibited strong negative correlations with the NDVI and strong positive correlations with the NDBI. The study’s results emphasize the interplay among the NDBI, LST, and UHI and an inverse relationship with the NDVI and NDBI, LST, and UHI. These findings hold implications for urban planning and policymaking, particularly in the context of resilient and sustainable land use planning and the UHI mitigation. This research underscores the intricate interplay among the NDBI, LST, and UHI, highlighting an inverse relationship with the NDVI. These findings hold crucial implications for resilient and sustainable urban planning, particularly in mitigating the UHI effects. Despite limited vacant spaces in Kayseri, geospatial techniques for identifying potential green spaces can facilitate swift UHI mitigation measures. Acknowledging Kayseri’s complex dynamics, future research should delve into the UHI responses to urban morphology and design, extending this methodology to analyze the UHI effects in other Turkish cities. This research contributes to a broader understanding of UHI dynamics and sustainable urban planning practices, offering valuable insights for policymakers, urban planners, and researchers alike.

Study’s Excerpt:• Uses Landsat OLI (2024), NDVI-LST-UHI analysis, and OLS regression for urban heat study.• Air temperature data improves reliability of study findings through ground truthing.• Confirms NDVI, LST, and UHI links, consistent with earlier urban heat effect studies.• Vegetation's cooling effect confirmed, but no new local mitigation strategies identified.• Findings stress urgent need for green infrastructure to tackle rising UHI from human activity.Full Abstract:Studies on Urban Heat Island (UHI) have become an important way to create sustainable and lively cities; it improves public health and enhances urban quality of life. An increase in the level of Land Surface Temperature (LST) and a corresponding rise in the urban temperature as UHI among many cities of Nigeria brings about more outbreaks of heat related diseases. The current research focused on the assessment of spatial patterns of LST and UHI in the Kaduna metropolis. Land sat 8, operational land imager (OLI) imagery of April 2024 was used for the research. Analysis was conducted through the determination of the Normalized Difference Vegetation Index (NDVI), vegetation density map, satellite brightness temperature, LST, and finally, UHI profile on ArcGIS 10.8 software. Results on vegetation density revealed that areas with very low vegetation cover recorded the highest (44.86%) while those with moderate vegetation cover had the lowest (12.06%). The findings also indicated that the highest (47.55%) percent of the study area experienced higher LST while only 8.93% experienced lower LST. Results also show that most (37.43%) percent of the research area recorded a high (6.55oC) rate of UHI, 16.38% recorded about 8.5oC, while only 1.87% experienced a low UHI of 3.4oC. Results of the regression analysis between NDVI and UHI indicated an inverse relationship between vegetation density and urban heat islands in such a way that, for every 1-unit increase in vegetation density, UHI decreases by ~19.63 units while the negative sign means more vegetation resulted in lower urban heat (cooling effect). In conclusion, the study indicated that the western and heart of the metropolis had high UHI profiles while the eastern part of the area and other areas along the water bodies experienced lower UHI. Based on these, the study recommends the provision of strategies such as plating trees which will help in reducing higher rate of heat, this is more especially during the hot and dry season.

Land surface temperature (LST) is an important yardstick of evaluating urban thermal effect. Researches on how the LST spatiotemporally respond to land use/cover (LUC) change can better understand the mechanism of urban heat island (UHI) formation, quantitatively examine the thermal contribution of urban biophysical components, and further ease the negative influence of accelerating urbanization. Using Landsat data, this study attempts to evaluate the spatial changes in land cover and its impacts on the urban thermal environment in the fastgrowing Shanghai metropolitan area (SMA). Based on the results of LUC classification and LST retrieval, we estimated the contribution proportion of different land cover on the thermal environment. Then, we performed the spatial concentric zone analysis and profile analysis according to the, urban-rural gradient theory. During the years from 2000 to 2015, the changes in observed values and trend of UHI over time, were highly co-related with the urban expansion of SMA. The results indicated that the UHI zone was gradually expanding between these 15 years, whereas the UHI intensity of the inner city in SMA was declining. The relative difference of thermal effect between the downtown and the outskirts was also decreasing. Additionally, we identified that the land cover composition has notably affected the urban thermal environment. In SMA, the substantial expansion of impervious surface (IS) has heavily influenced the urban thermal effect; in contrast, the spatial adjustments of urban greenspace infrastructure including vegetation and water, effectively relieve UHI phenomenon and enhance the effect of urban greenspace cooling island (UGCI). The finding is expected to provide references and clues for the decision-makers for optimizing and creating appropriate sustainable urban development strategies.