scholarly journals Analyses of urban pavement surface temperatures

2015 ◽  
Vol 10 (3) ◽  
pp. 239-246 ◽  
Author(s):  
Aleksandra Deluka-Tibljaš ◽  
Sanja Šurdonja ◽  
Sergije Babić ◽  
Marijana Cuculić
Keyword(s):  
Urban Areas ◽  
Concrete Surface ◽  
City Centre ◽  
Heat Islands ◽  
Pavement Surface ◽  
Island Effect ◽  
Surface Temperatures ◽  
Additional Heating ◽  
Air Temperatures ◽  
Surface Materials

Heat islands are areas that have higher air temperatures than their surroundings. It has been proven that the use of certain types of pavement surface materials contributes to the occurrence of heat islands. The heat island effect is dominant in urban areas, mainly in city centres. To identify potentially favourable pavement surface materials that are suitable for the use on surfaces in urban areas, an extensive analysis of in-place material temperatures was conducted in the city centre of Rijeka (Croatia) during the summer of 2011 and 2012. The measurements included temperatures of pavement surfaces made of asphalt, concrete and stone. The analysis results identified local materials whose use help to reduce or mitigate the effect of additional heating in the urban environment caused by emission of heat from pavement surfaces. In terms of additional heating of urbanized areas, asphalt has proven to be significantly less favourable than other analysed materials. In addition to the materials selected for the use in wearing courses, their characteristics and the microclimates of the locations where they will be placed must be taken into consideration. Among the standard paving materials, in terms of heating and temperature, concrete is more favourable than asphalt because the differences between concrete surface temperatures and air temperatures are significantly smaller than between asphalt surface temperatures and air temperatures. Stone surfaces have proven to be the most favourable. The analysis results presented can be used to establish clear guidelines for using specific materials under specific conditions.

Emergence of opposite trends in daytime and night-time urban heat island intensities in England

2020 ◽  
Author(s):  
Eunice Lo ◽  
Dann Mitchell ◽  
Sylvia Bohnenstengel ◽  
Mat Collins ◽  
Ed Hawkins ◽  
...  
Keyword(s):  
Urban Heat Island ◽  
Urban Areas ◽  
Urban Land Use ◽  
Urban Heat Islands ◽  
Urban Heat Island Effect ◽  
Heat Island ◽  
Night Time ◽  
Heat Islands ◽  
Island Effect ◽  
Urban Heat

<p>Urban environments are known to be warmer than their sub-urban or rural surroundings, particularly at night. In summer, urban heat islands exacerbate the occurrence of extreme heat events, posing health risks to urban residents. In the UK where 90% of the population is projected to live in urban areas by 2050, projecting changes in urban heat islands in a warming climate is essential to adaptation and urban planning.</p><p>With the use of the new UK Climate Projections (UKCP18) in which urban land use is constant, I will show that both summer urban and sub-urban temperatures are projected to increase in the 10 most populous built-up areas in England between 1980 and 2080. However, differential warming rates in urban and sub-urban areas, and during day and at night suggest a trend towards a reduced daytime urban heat island effect but an enhanced night-time urban heat island effect. These changes in urban heat islands have implications on thermal comfort and local atmospheric circulations that impact the dispersion of air pollutants. I will further demonstrate that the opposite trends in daytime and night-time urban heat island effects are projected to emerge from current variability in more than half of the studied cities below a global mean warming of 3°C above pre-industrial levels.</p>

The Footprint of Urban Areas on Global Climate as Characterized by MODIS

2005 ◽  
Vol 18 (10) ◽  
pp. 1551-1565 ◽  
Author(s):  
Menglin Jin ◽  
Robert E. Dickinson ◽  
Da Zhang
Keyword(s):  
Land Cover ◽  
Skin Temperature ◽  
Urban Areas ◽  
Climate Models ◽  
Global Analysis ◽  
The United States ◽  
Climate Impact ◽  
Surface Temperatures ◽  
Air Temperatures ◽  
Seasonal And Diurnal Variations

Abstract One mechanism for climate change is the collected impact of changes in land cover or land use. Such changes are especially significant in urban areas where much of the world’s population lives. Satellite observations provide a basis for characterizing the physical modifications that result from urbanization. In particular, the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument on the National Aeronautics and Space Administration (NASA) Terra satellite measures surface spectral albedos, thermal emissivities, and radiative temperatures. A better understanding of these measurements should improve our knowledge of the climate impact of urbanization as well as our ability to specify the parameters needed by climate models to compute the impacts of urbanization. For this purpose, it is useful to contrast urban areas with neighboring nonurban surfaces with regard to their radiative surface temperatures, emissivities, and albedos. Among these properties, surface temperatures have been most extensively studied previously in the context of the “urban heat island” (UHI). Nevertheless, except for a few detailed studies, the UHI has mostly been characterized in terms of surface air temperatures. To provide a global analysis, the zonal average of these properties are presented here measured over urban areas versus neighboring nonurban areas. Furthermore, individual cities are examined to illustrate the variations of these variables with land cover under different climate conditions [e.g., in Beijing, New York, and Phoenix (a desert city of the United States)]. Satellite-measured skin temperatures are related to the surface air temperatures but do not necessarily have the same seasonal and diurnal variations, since they are more coupled to surface energy exchange processes and less to the overlying atmospheric column. Consequently, the UHI effects from skin temperature are shown to be pronounced at both daytime and nighttime, rather than at night as previously suggested from surface air temperature measurements. In addition, urban areas are characterized by albedos much lower than those of croplands and deciduous forests in summer but similar to those of forests in winter. Thus, urban surfaces can be distinguished from nonurban surfaces through use of a proposed index formed by multiplying skin temperature by albedo.

Automated detection of urban heat islands based on satellite imagery, digital surface models, and a low-cost sensor network                                     

2021 ◽  
Author(s):  
Sebastian Schlögl ◽  
Nico Bader ◽  
Julien Gérard Anet ◽  
Martin Frey ◽  
Curdin Spirig ◽  
...  
Keyword(s):  
Climate Change ◽  
Air Temperature ◽  
Rural Areas ◽  
Urban Areas ◽  
Low Cost ◽  
Urban Heat Islands ◽  
Heat Islands ◽  
Micro Scale ◽  
Air Temperatures ◽  
Urban Heat

<p>Today, more than half of the world’s population lives in urban areas and the proportion is projected to increase further in the near future. The increased number of heatwaves worldwide caused by the anthropogenic climate change may lead to heat stress and significant economic and ecological damages. Therefore, the growth of urban areas in combination with climate change can increase future mortality rates in cities, given that cities are more vulnerable to heatwaves due to the greater heat storage capacity of artificial surfaces towards higher longwave radiation fluxes.</p><p>To detect urban heat islands and resolve the micro-scale air temperature field in an urban environment, a low-cost air temperature network, including 450 sensors, was installed in the Swiss cities of Zurich and Basel in 2019 and 2020. These air temperature data, complemented with further official measurement stations, force a statistical air temperature downscaling model for urban environments, which is used operationally to calculate hourly micro-scale air temperatures in 10 m horizontal resolution. In addition to air temperature measurements from the low-cost sensor network, the model is further forced by albedo, NDVI, and NDBI values generated from the polar-orbiting satellite Sentinel-2, land surface temperatures estimated from Landsat-8, and high-resolution digital surface and elevation models.</p><p>Urban heat islands (UHI) are processed averaging hourly air temperatures over an entire year for each grid point, and comparing this average to the overall average in rural areas. UHI effects can then be correlated to high-resolution local climate zone maps and other local factors.</p><p>Between 60-80 % of the urban area is modeled with an accuracy below 1 K for an hourly time step indicating that the approach may work well in different cities. However, the outcome may depend on the complexity of the cities. The model error decreases rapidly by increasing the number of spatially distributed sensor data used to train the model, from 0 to 70 sensors, and then plateaus with further increases. An accuracy below 1 K can be expected for more than 50 air temperature measurements within the investigated cities and the surrounding rural areas. </p><p>A strong statistical air temperature model coupled with atmospheric boundary layer models (e.g. PALM-4U, MUKLIMO, FITNAH) will aid to generate highly resolved urban heat island prediction maps that help decision-makers to identify local heat islands easier. This will ensure that financial resources will be invested as efficiently as possible in mitigation actions.</p>

scholarly journals Effects of Albedo and Thermal Inertia on Pavement Surface Temperatures with Convective Boundary Conditions—A CFD Study

Processes ◽  
2021 ◽  
Vol 9 (11) ◽  
pp. 2078
Author(s):  
Tathagata Acharya ◽  
Brooke Riehl ◽  
Alan Fuchs
Keyword(s):  
Building Materials ◽  
Thermal Inertia ◽  
Concrete Surface ◽  
Published Data ◽  
Concrete Pavements ◽  
Ambient Conditions ◽  
Convective Boundary ◽  
Ambient Temperatures ◽  
Pavement Surface ◽  
Surface Temperatures

The urban heat island (UHI) effect increases the ambient temperatures in cities and alters the energy budget of building materials. Urban surfaces such as pavements and roofs absorb solar heat and re-emit it back into the atmosphere, contributing towards the UHI effect. Over the past few decades, researchers have identified albedo and thermal inertia as two of the most significant thermal properties that influence pavement surface temperatures under a given solar load. However, published data for comparisons of albedo and thermal inertia are currently inadequate. This work focuses on asphalt and concrete as two important materials used in the construction of pavements. Computational fluid dynamics (CFD) analyses are performed on asphalt and concrete pavements with the same dimensions and under the same ambient conditions. Under given conditions, the pavement top surface temperature is evaluated with varying albedo and thermal inertia values. The results show that the asphalt surface temperatures are consistently higher than the concrete surface temperatures. Surface temperatures under solar load reduce with increasing albedo and thermal inertia values for both asphalt and concrete pavements. The CFD results show that increasing the albedo is more effective in reducing pavement surface temperatures than increasing the thermal inertia.

The Benefits of Tree Shade and Turf on Globe and Surface Temperatures in an Urban Tropical Environment

2020 ◽  
Vol 46 (3) ◽  
pp. 228-244
Author(s):  
Lai Fern Ow ◽  
Subhadip Ghosh ◽  
Mohamed Lokman Mohd Yusof
Keyword(s):  
Thermal Comfort ◽  
Urban Areas ◽  
Mitigation Strategies ◽  
Urban Heat Islands ◽  
Outdoor Thermal Comfort ◽  
Mitigation Measures ◽  
Heat Islands ◽  
Ambient Temperatures ◽  
Surface Temperatures ◽  
Island State

The process of urbanisation increases temperature and alters the thermal comfort in cities. Urban heat islands (UHIs) result in the rise of ambient temperatures. For example, in the densely populated island state of Singapore, the UHI intensity was some 4.5 °C. Such elevation in heat can negatively impact outdoor thermal comfort and may give rise to serious health problems. The present study investigated the benefits of trees and turf as mitigation strategies for urban areas. Short- and long-term observations were made for surface and globe temperatures over smaller plots of vegetation and hard surfaces involving tree shade and full sun. Similar observations were investigated over a larger extent of vegetation across concrete, asphalt, and turf within an urban park setting. The presence of turf and shade from trees greatly affected surface temperatures, and the effect was most pronounced when both were present. The presence of turf reduced surface temperatures by up to 10 °C, while tree shade led to a 12 °C reduction. Globe temperatures showed that the presence of turf and shading reduced temperatures between 5 and 10 °C. These results suggest that turf and trees can effectively cool surfaces and improve outdoor thermal comfort. The results of this study can be applied to urban planning of greenery and can be used as a reference for other tropical cities with similar climates that are also working to develop mitigation measures to improve the liveability of their cities.

scholarly journals Understanding Spatial Variability of NO2 in Urban Areas Using Spatial Modelling and Data Fusion Approaches

Atmosphere ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 179
Author(s):  
Said Munir ◽  
Martin Mayfield ◽  
Daniel Coca
Keyword(s):  
Data Fusion ◽  
Spatial Variability ◽  
Urban Areas ◽  
Road Traffic ◽  
Dispersion Model ◽  
Low Cost ◽  
Spatial Modelling ◽  
City Centre ◽  
Small Scale ◽  
The City

Small-scale spatial variability in NO2 concentrations is analysed with the help of pollution maps. Maps of NO2 estimated by the Airviro dispersion model and land use regression (LUR) model are fused with measured NO2 concentrations from low-cost sensors (LCS), reference sensors and diffusion tubes. In this study, geostatistical universal kriging was employed for fusing (integrating) model estimations with measured NO2 concentrations. The results showed that the data fusion approach was capable of estimating realistic NO2 concentration maps that inherited spatial patterns of the pollutant from the model estimations and adjusted the modelled values using the measured concentrations. Maps produced by the fusion of NO2-LCS with NO2-LUR produced better results, with r-value 0.96 and RMSE 9.09. Data fusion adds value to both measured and estimated concentrations: the measured data are improved by predicting spatiotemporal gaps, whereas the modelled data are improved by constraining them with observed data. Hotspots of NO2 were shown in the city centre, eastern parts of the city towards the motorway (M1) and on some major roads. Air quality standards were exceeded at several locations in Sheffield, where annual mean NO2 levels were higher than 40 µg/m3. Road traffic was considered to be the dominant emission source of NO2 in Sheffield.

scholarly journals Quantifying the Independent Influences of Land Cover and Humidity on Microscale Urban Air Temperature Variation in Hot Summer: Methods of Path Analysis and Genetic SVR

Atmosphere ◽  
2020 ◽  
Vol 11 (12) ◽  
pp. 1377
Author(s):  
Weifang Shi ◽  
Nan Wang ◽  
Aixuan Xin ◽  
Linglan Liu ◽  
Jiaqi Hou ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Land Cover ◽  
Path Analysis ◽  
Temperature Variation ◽  
Direct Effect ◽  
Air Temperature ◽  
Urban Areas ◽  
Support Vector ◽  
Urban Air ◽  
Air Temperatures

Mitigating high air temperatures and heat waves is vital for decreasing air pollution and protecting public health. To improve understanding of microscale urban air temperature variation, this paper performed measurements of air temperature and relative humidity in a field of Wuhan City in the afternoon of hot summer days, and used path analysis and genetic support vector regression (SVR) to quantify the independent influences of land cover and humidity on air temperature variation. The path analysis shows that most effect of the land cover is mediated through relative humidity difference, more than four times as much as the direct effect, and that the direct effect of relative humidity difference is nearly six times that of land cover, even larger than the total effect of the land cover. The SVR simulation illustrates that land cover and relative humidity independently contribute 16.3% and 83.7%, on average, to the rise of the air temperature over the land without vegetation in the study site. An alternative strategy of increasing the humidity artificially is proposed to reduce high air temperatures in urban areas. The study would provide scientific support for the regulation of the microclimate and the mitigation of the high air temperature in urban areas.

Developing physical resilience strategies in passive defense according to identification of endangered areas of urban environments (case study: Ahvaz city)

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Mozhdeh Pouryarmohammadi ◽  
Hasan Ahmadi ◽  
AliAkbar Salaripour
Keyword(s):  
Risk Assessment ◽  
At Risk ◽  
Urban Form ◽  
Urban Areas ◽  
Quality Function Deployment ◽  
Quantitative Methods ◽  
City Centre ◽  
Urban Resilience ◽  
Content Type ◽  
Oil Companies

Purpose This paper aims to focus on reducing the vulnerability of Ahvaz city against urban disasters and lowering the number of casualties and amount of financial losses using modern approaches to develop resilience strategies that can increase urban safety to an acceptable level. The strategic situation of Ahvaz city, because of its abundant resources, the war experience and its location on the boundary regions of Iran, highlights its significance. Ahvaz has a high population and an extended texture, and the existence of extraordinary constructions increases the importance of physical resilience in this city. Design/methodology/approach The present study investigates built environment aspects such as the urban structure, the urban form, land-use proximity pattern, urban road network and crucial and vulnerable centres in Ahvaz, using a combination of qualitative and quantitative methods. Hence, the areas at risk in Ahvaz were identified and illustrated in a comprehensive risk assessment map, and then, by using the strengths, weaknesses, opportunities and threats technique and finally by using the Delphi method, some strategies and plans were presented to reduce the level of vulnerability in Ahvaz. Then, these strategies are prioritized by applying quality function deployment (QFD) technique. Findings The risk assessment result shows that most parts of Ahvaz’s urban areas are highly at risk. The central and northern parts of Ahvaz have the highest vulnerability at a time of crisis. These zones include district 1 (city centre) and districts 2, 3 and 7 at the city’s margins. The result of QFD process showed that the essential urban resilience strategy is to positively consider the passive defence studies with a physical resilience approach. Also, the proper distribution of strategic points in the city, moving the industrial and oil companies from the peripheral area, and facilitating access to vital, crucial centres to support urban regions are considered the most effective strategic plans. Originality/value This paper, with an integrated approach, examines and prioritizes the main physical problems of Ahvaz city based on the spatial analysis and opinions of experts. The physical strategies presented in this paper can significantly reduce the risks and increase the urban resilience of Ahvaz city in the face of crisis.

scholarly journals Evaporation from (Blue-)Green Roofs: Assessing the Benefits of a Storage and Capillary Irrigation System Based on Measurements and Modeling

Water ◽  
2018 ◽  
Vol 10 (9) ◽  
pp. 1253 ◽  
Author(s):  
Dirk Cirkel ◽  
Bernard Voortman ◽  
Thijs van Veen ◽  
Ruud Bartholomeus
Keyword(s):  
Energy Balance ◽  
Urban Areas ◽  
Evaporation Rate ◽  
Climate Adaptation ◽  
Irrigation System ◽  
Green Roof ◽  
Green Roofs ◽  
C3 Plants ◽  
Rapid Decline ◽  
Air Temperatures

Worldwide cities are facing increasing temperatures due to climate change and increasing urban density. Green roofs are promoted as a climate adaptation measure to lower air temperatures and improve comfort in urban areas, especially during intensive dry and warm spells. However, there is much debate on the effectiveness of this measure, because of a lack of fundamental knowledge about evaporation from different green roof systems. In this study, we investigate the water and energy balance of different roof types on a rooftop in Amsterdam, the Netherlands. Based on lysimeter measurements and modeling, we compared the water and energy balance of a conventional green roof with blue-green roofs equipped with a novel storage and capillary irrigation system. The roofs were covered either with Sedum or by grasses and herbs. Our measurements and modeling showed that conventional green roof systems (i.e., a Sedum cover and a few centimeters of substrate) have a low evaporation rate and due to a rapid decline in available moisture, a minor cooling effect. Roofs equipped with a storage and capillary irrigation system showed a remarkably large evaporation rate for Sedum species behaving as C3 plants during hot, dry periods. Covered with grasses and herbs, the evaporation rate was even larger. Precipitation storage and capillary irrigation strongly reduced the number of days with dry-out events. Implementing these systems therefore could lead to better cooling efficiencies in cities.

scholarly journals The Fingerprint of Climate Change and Urbanization in South Korea

Atmosphere ◽  
2018 ◽  
Vol 9 (7) ◽  
pp. 273 ◽  
Author(s):  
Won-Ho Nam ◽  
Guillermo Baigorria ◽  
Eun-Mi Hong ◽  
Taegon Kim ◽  
Yong-Sang Choi ◽  
...  
Keyword(s):  
Climate Change ◽  
South Korea ◽  
Urban Areas ◽  
Temporal Trends ◽  
Weather Data ◽  
Maximum Temperature ◽  
Island Effect ◽  
Temperature Trends ◽  
Agricultural Areas ◽  
Precipitation And Temperature

Understanding long-term changes in precipitation and temperature patterns is important in the detection and characterization of climate change, as is understanding the implications of climate change when performing impact assessments. This study uses a statistically robust methodology to quantify long-, medium- and short-term changes for evaluating the degree to which climate change and urbanization have caused temporal changes in precipitation and temperature in South Korea. We sought to identify a fingerprint of changes in precipitation and temperature based on statistically significant differences at multiple-timescales. This study evaluates historical weather data during a 40-year period (1973–2012) and from 54 weather stations. Our results demonstrate that between 1993–2012, minimum and maximum temperature trends in the vicinity of urban and agricultural areas are significantly different from the two previous decades (1973–1992). The results for precipitation amounts show significant differences in urban areas. These results indicate that the climate in urbanized areas has been affected by both the heat island effect and global warming-caused climate change. The increase in the number of rainfall events in agricultural areas is highly significant, although the temporal trends for precipitation amounts showed no significant differences. Overall, the impacts of climate change and urbanization in South Korea have not been continuous over time and have been expressed locally and regionally in terms of precipitation and temperature changes.

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