ETFE-foils in pneumatically retractable civil engineering structures

Revealing the response of urban heat island effect to water body evaporation from main urban and suburb areas

Urban Heat Island (UHI) effects adversely impact weather, air quality, and climate. Previous studies have attributed UHI effects to localized, surface processes. Based on an observational and modeling study of an extreme UHI (heat wave) episode in the Baltimore metropolitan region, we find that upstream urbanization exacerbates UHI effects and that meteorological consequences of extra‐urban development can cascade well downwind. Under southwesterly wind, Baltimore, MD, experienced higher peak surface temperatures and higher pollution concentrations than did the larger urban area of Washington, DC. Ultra‐high resolution numerical simulations with National Land Cover Data (NLCD) of 2001 show a nonlocal, dynamical contribution to UHI effects; when the upstream urban area is replaced by natural vegetation (in the model) the UHI effects could be reduced by more than 25%. These findings suggest that judicious land‐use and urban planning, especially in rapidly developing countries, could help alleviate UHI consequences including heat stress and smog.

<h3>Abstract</h3> Urban heat islands, where temperatures are elevated relative to non-urban surrounds, are near-ubiquitous in cities globally. Yet, the magnitude and form of urban heat islands in the tropics, where heat has a large morbidity and mortality burden, is less well understood, especially for socioeconomically diverse communities such as those living in urban informal settlements. We utilised 29 years of Landsat satellite-derived surface temperature, corroborated by <i>in situ</i> measurements, to provide a detailed spatial and temporal assessment of urban heat islands in Makassar, Indonesia, a city that is representative of rapidly growing urban settlements across the tropics. We did so with explicit consideration of vulnerable communities living informally. Our analysis identified surface urban heat islands of up to 9.2 °C in long-urbanised parts of the city and 6.3 °C in informal settlements, the seasonal patterns of which were driven by change in non-urban areas rather than in urban areas themselves. In recently urbanised areas, the majority of urban heat island increase occurred before areas became 50% urbanised. As tropical cities continue to expand we expect that urban heat islands will develop quickly as land is urbanised, whereas the established heat island in long-urbanised areas will remain stable in response to city expansion. Green and blue space protect some informal settlements from the worst urban heat islands and maintenance of such space will be essential to mitigate the growing heat burden from urban expansion and anthropogenic climate change. We advocate for green space to be prioritised in urban planning, redevelopment and informal settlement upgrading programs, with consideration of the unique environmental and socioeconomic context of tropical cities. <h3>Highlights</h3> Long-term, fine-scale data are essential to understand the dynamics of urban heat Surface heat islands reached 9.2 °C in the urban core, 6.3 °C in informal settlements <i>In situ</i> data support the use of remote sensing for heat island characterisation The majority of heat island growth occurred before land was 50% urbanised Green and blue space can mitigate heat in informal settlements

Two Landsat scenes (acquired on 21 May 1986 and 19 May 2000) were used to examine differences in surface temperature inside and outside the city of Abu Dhabi and to examine a potential relationship between vegetation abundance and drop in temperatures. Land cover maps of Abu Dhabi city and its surroundings spanning the period 1986–2000 were created using multispectral classification, and vegetation abundance maps using the vegetation fraction index and surface temperature maps from Landsat were created to study their spatial relationships using GIS-based multivariate statistical analysis. Differences in surface temperature between urban areas and their non-urban surroundings were also studied to assess any urban heat island (UHI) effect. A map showing the magnitude of UHI effect was created and linked to the vegetation abundance map. Results show that the UHI effect in major UAE urban centres is minimal; however, more investigation is needed to confirm this hypothesis for other UAE cities.

Based on the land surface temperature (LST), the land cover classification map, vegetation coverage, and surface evapotranspiration derived from EOS-MODIS satellite data, and by the use of GIS spatial analytic technique and multivariate statistical analysis method, the urban heat island (UHI) spatial distribution of the diurnal and seasonal variabilities and its driving forces are studied in Beijing city and surrounding areas in 2001. The relationships among UHI distribution and landcover categories, topographic factor, vegetation greenness, and surface evapotranspiration are analyzed. The results indicate that: (i) The significant UHI occur in Beijing city areas in the four seasons due to high heat capacity and multi-reflection of compression building, as well as with special topographic features of its three sides surrounded by mountains, especially in the summer. The UHI spatial distribution is corresponding with the urban geometry structure profile. The LST difference is approximately 4-6℃between Beijing city and suburb areas, comparatively is 8- 10℃between Beijing city area and outer suburb area in northwestern regions. (ii) The UHI distribution and intensity in daytime are different from nighttime in Beijing city area, the nighttime UHI is obvious. However, in the daytime, the significant UHI mainly appears in the summer, the autumn takes second place, and the UHI in the winter and the spring seem not obvious. The surface evapotranspiration in suburb areas is larger than that in urban areas in the summer, and high latent heat exchange is evident, which leads to LST difference between city area and suburb area. (iii) The reflection of surface landcover categories is sensitive to the UHI, the correlation between vegetation greenness and UHI shows obviously negative. The scatterplot shows that there is the negative correlation between NDVI and LST (R2 = 0.6481). The results demonstrate that the vegetation greenness is an important factor for reducing the UHI, and large-scale construction of greenbelts can considerably reduce the UHI effect.

To study the urban heat island (UHI) effect in the mountainous areas of Chongqing, the UHI indexes for the Chongqing urban agglomerations were investigated in the present study. This study is based on data from 34 national weather stations and more than 2000 regional automated weather stations in Chongqing, Defense Meteorological Satellite Program/Operational Linescan System (DMSP/OLS) nighttime light data, and 30-m high-resolution land use data and Moderate Resolution Imaging Spectroradiometer (MODIS) land surface temperature remote sensing data for Chongqing in 2015. Moreover, the influences of three background temperature calculation methods on the UHI effect were compared. The results showed that, if only the land use data and the city clustering algorithm (CCA) were used to divide the urban and suburban areas, the strong UHI index of Chongqing exhibited an abnormal increase in the years with extremely high temperatures, and the corresponding divided suburban and urban areas had relatively large differences in altitudes, thereby overestimating the UHI index. Therefore, in the present study, a new method for dividing the urban and suburban areas based on the combined CCA and light intensity data and a division method with the altitudes calibrated on this basis were designed. Both methods were able to satisfactorily reduce the influence of extreme climate years and excessively large differences in altitudes on the UHI index calculations and provide a new approach for future studies of the UHI index for mountainous areas with large altitude differences.

Inter-seasonal characterization and correlation of Surface Urban Heat Island (SUHI) and Canopy Urban Heat Island (CUHI) in the urbanized environment of Delhi

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.

The urban heat island (UHI) effect has emerged in the literature as a major challenge to urban well-being, primarily driven by increasing urbanization. To address this challenge, this study investigates the spatiotemporal pattern of the UHI in the fast-growing city of Kisangani and within its urban–rural gradient from 2000 to 2024 using land surface temperature (LST) data from the MODIS 11A2 V6.1 product. Inferential and descriptive statistics were applied to examine the patterns of UHI and the relationships between the LST, building volume density (BVD), and vegetation density expressed by the Normalized Difference Vegetation Index (NDVI). The results showed that the spatial extent of the moderate UHI gradually increased from 16 km2 to 38 km2, while the high UHI increased from 9 km2 to 19 km2. Furthermore, although high UHI values (0.2 &lt; UHI ≤ 0.3) are observed in urban areas and significant differences in UHI variations are detected across urban, peri-urban, and rural zones, the results indicate that the mean UHI in Kisangani’s urban areas remains below 0.2. Therefore, based on average UHI variations, Kisangani’s urban zones exhibit moderate disparities in LST compared to rural areas. Moreover, the LST variations significantly correlate with the building volume and vegetation densities. However, the influence of vegetation density as a predictor of LST gradually decreases while the influence of building volume density increases over time, suggesting the need to implement a synergistic development pathway to manage the interactions between urbanization, landscape change, and ecosystem service provision. This integrated approach may represent a crucial solution for mitigating the UHI effect in regions categorized as high-temperature zones.

Sensitivity analysis of physical parameterizations in WRF for urban climate simulations and heat island mitigation in Montreal

The global rise of urbanization has led to the formation of surface urban heat islands and surface urban cool islands. Urban heat islands have been shown to increase thermal discomfort, which increases heat stress and heat-related diseases. In Kuwait, a hyper-arid desert climate, most of the population lives in urban and suburban areas. In this study, we characterized the spatial distribution of land surface temperatures and investigated the presence of urban heat and cool effects in Kuwait. We used historical Moderate-Resolution Imaging Spectroradiometer (MODIS) Terra satellite 8-day composite land surface temperature (LST) from 2001 to 2017. We calculated the average LSTs of the urban/suburban governorates and compared them to the average LSTs of the rural and barren lands. We repeated the analysis for daytime and nighttime LST. During the day, the temperature difference (urban/suburban minus versus governorates) was −1.1 °C (95% CI; −1.2, −1.00, p < 0.001) indicating a daytime urban cool island. At night, the temperature difference (urban/suburban versus rural governorates) became 3.6 °C (95% CI; 3.5, 3.7, p < 0.001) indicating a nighttime urban heat island. In light of rising temperatures in Kuwait, this work can inform climate change adaptation efforts in the country including urban planning policies, but also has the potential to improve temperature exposure assessment for future population health studies.

Quantifying urban heat island and pollutant nexus: A novel geospatial approach

The increasing frequency of extreme heat events due to climate change calls for a deeper understanding of the factors contributing to heat stress-related morbidity and mortality. Urban areas, with their high population densities, are especially vulnerable due to the urban heat island (UHI) effect, which intensifies temperatures compared to rural surroundings. Traditional heat stress assessments often focus solely on air temperature (Ta), overlooking other factors such as humidity, wind speed, and solar radiation important for the thermal comfort. Spatial data on heat stress is often lacking at fine spatial resolutions, making the use of LST a common. However the relationship between Ta, LST and thermal comfort metrics such as Universal Thermal Climate Index (UTCI) or Humidex are not yet well understood. &amp;#160;To address this gap, we conducted a spatio-temporal assessment of thermal comfort metrics, LST and Ta across Hesse, Germany, using 1 km scale data. By examining temperature anomalies (&amp;#916;T), the difference between local and comparable rural background temperatures, we quantify the urban impact on heat stress while minimizing broader climatic influences. Diurnal and spatial patterns of temperature variations and thermal conditions are examined across different land use types and urban forms. Satellite-derived parameters were also incorporated to assess regional heat risk in areas lacking local measurement data. &amp;#160;Our findings reveal a stronger UHI effect in &amp;#916;Humidex (max. 4.3&amp;#176;C) compared to &amp;#916;Ta (max. 2.9&amp;#176;C) and &amp;#916;LST (max. 3.4&amp;#176;C), indicating that reliance on LST or Ta alone might underestimates the full extent of heat stress of the urban population. This is particularly significant as nearly one-third of the population in Hesse (30.4% for Ta, 25.6% for Humidex, and 34.7% for LST) lives in areas where temperatures exceed baseline levels both during the day and at night. The duration of temperature exceedance is consistently longer in urban areas, with average values of 3.8 hours and 2.8 hours of the diurnal cycle for &amp;#916;Humidex and &amp;#916;Ta, respectively, compared to 0.7 hours and 0.4 hours in rural areas. Densely built areas, where nighttime cooling deficits persist longer, are particularly vulnerable, while inhabitants of open urban areas experience more moderate heat stress. These results emphasize the need to incorporate thermal comfort metrics that account for multiple parameters when evaluating the UHI effect. Although LST is commonly used as a substitute in UHI studies, its correlation with Ta and Humidex varies both spatially and temporally, warranting cautious application.

The Urban Heat Island (UHI) effect refers to the phenomenon where urban areas experience significantly higher temperatures than their rural surroundings due to human activities and modifications, such as replacing natural land cover with impervious surfaces, reducing vegetation, and increasing heat-absorbing materials. Kütahya central district has a dense population and building layout, which contributes to the intense UHI. Geographic Information System (GIS) and its tools are widely used in assessing UHI in urban areas, providing insights for both researchers and local authorities. Landsat-8 images acquired on August 8, 2023 (Path: 179, Row: 33, Cloud Cover: 0%) were utilized to create the Urban Heat Island (UHI) map for the study area. Through spatial analysis using Landsat-8 data for Kütahya city center, six different classes were defined, with the UHI map created using land surface temperature values. The highest and lowest UHI values vary between 4.245°C and -3.457°C. It has been observed that the average UHI increases by 12% in areas lacking dense building structures, characterized by rock surfaces and limited green areas. Conversely, in areas with parks, forests, and sparse settlements, the UHI decreases by 10%. With this study, a comprehensive evaluation of UHI was conducted for Kütahya city center. While the results obtained are expected to be an important resource for researchers and local authorities, they are also anticipated to be beneficial in the fields of engineering geology, urban geology, and urban planning.

With the ongoing rapid urbanisation, humans enjoy the comfort of living with the use of advanced technology and infrastructure, without consideration towards the pollution produced daily, such as waste, heat, and exhaust gas emissions. Human-induced climate change has resulted in extreme weather and climate events, causing a consequential increase in the urban heat island effect. A large amount of radiant heat is focused in the city area, threatening the threshold of comfort in urban living, affecting our future generations to come. Therefore, this paper discusses how this phenomenon could be mitigated through a few design approaches. The existence of green roofs helps reduce the direct absorption of heat in buildings while water bodies help lower the surrounding temperature of a place. Additionally, using high reflectivity and spectral emissivity materials in buildings can also lower heat absorption into a building. Also, the design of urban wind corridors increases airflow into an area, hence cooling the surrounding temperature. When these steps are strategically incorporated into a design, the amount of heat could be significantly reduced, hence extenuating the urban heat island effect. However, more in-depth research is needed to ensure that it could successfully palliate the urban heat island effect in a city. It is hoped that this study could be a comprehensive guide to designers and engineers, or any individuals in the field of architecture and urban design in tackling the problem, hence achieving their target in eliminating the urban heat island effect in future works.