The effect of Urban Heat Island (UHI) 

The effect of Urban Heat Island (UHI) 

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Conference Paper
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Today rapid urbanization is a major challenge for many cities. In 2007 urban population started to exceed the rural population. Increasingly, scholars and governments discuss the effects of this trend on future development of cities. It is obvious that any kind of urban development should be controlled and regulated, otherwise the outcome could lea...

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Context 1
... situation directly influences the overall air ambient temperature of the urban area. As a result, the urban area becomes warmer in comparison to the surrounding area. At the moment, this phenomenon is well-accepted and known as Urban Heat Island (UHI) effect ( Figure 1). The UHI clearly defined as a temperature difference between the urban and rural As stated before, the wide range of the natural and the man-made factors include seasons, cloud cover, wind speed, sunlight, urban canyon geometry, surface material, anthropogenic heat, and etc. are responsible for emerging of this ...
Context 2
... situation directly influences the overall air ambient temperature of the urban area. As a result, the urban area becomes warmer in comparison to the surrounding area. At the moment, this phenomenon is well-accepted and known as Urban Heat Island (UHI) effect ( Figure 1). The UHI clearly defined as a temperature difference between the urban and rural As stated before, the wide range of the natural and the man-made factors include seasons, cloud cover, wind speed, sunlight, urban canyon geometry, surface material, anthropogenic heat, and etc. are responsible for emerging of this ...

Citations

... (c) Heat could be considered as a pollutant since the built-up area tends to be warmer than the adjacent area. The generation of heat in an urban area is the climatic reaction to disruptions caused by urban development known as UHI (Fuladlu et al., 2018a;Marsh & Grossa, 1996). The urbanization process transforms the natural material into artificial with the minimum ability of evapotranspiration. ...
... As Lauder, Sari, Suwartha, and Tjahjono (2015) stated, campuses "have been conceptualized as 'small cities' in their quest to attain sustainability 2. LITERATURE REVIEW Thermal balance varies due to clothing, physical activity, and environmental parameters. In this context, environmental parameters are an array of geographical location (Mohajerani, Bakaric, & Jeffrey-Bailey, 2017;Robitu, Musy, Inard, & Groleau, 2006), meteorological situation (Chen & Ng, 2012), urban form (Andreou, 2013;Fuladlu, 2019Fuladlu, , 2020Fuladlu, Riza, & İlkan, 2018a, 2018bRobitu et al., 2006), surface materials (Andreou, 2013;Fuladlu et al., 2018a;Jamei, Rajagopalan, Seyedmahmoudian, & Jamei, 2016;Mohajerani et al., 2017;Robitu et al., 2006), amount of vegetation and watershed (Andreou, 2013;Jamei et al., 2016;Mohajerani et al., 2017;Robitu et al., 2006), and anthropogenic pollution (Fuladlu & Altan, 2021;Fuladlu et al., 2018a;Marsh & Grossa, 1996;Robitu et al., 2006). The COS's microclimate is a combined response to these environmental parameters. ...
... As Lauder, Sari, Suwartha, and Tjahjono (2015) stated, campuses "have been conceptualized as 'small cities' in their quest to attain sustainability 2. LITERATURE REVIEW Thermal balance varies due to clothing, physical activity, and environmental parameters. In this context, environmental parameters are an array of geographical location (Mohajerani, Bakaric, & Jeffrey-Bailey, 2017;Robitu, Musy, Inard, & Groleau, 2006), meteorological situation (Chen & Ng, 2012), urban form (Andreou, 2013;Fuladlu, 2019Fuladlu, , 2020Fuladlu, Riza, & İlkan, 2018a, 2018bRobitu et al., 2006), surface materials (Andreou, 2013;Fuladlu et al., 2018a;Jamei, Rajagopalan, Seyedmahmoudian, & Jamei, 2016;Mohajerani et al., 2017;Robitu et al., 2006), amount of vegetation and watershed (Andreou, 2013;Jamei et al., 2016;Mohajerani et al., 2017;Robitu et al., 2006), and anthropogenic pollution (Fuladlu & Altan, 2021;Fuladlu et al., 2018a;Marsh & Grossa, 1996;Robitu et al., 2006). The COS's microclimate is a combined response to these environmental parameters. ...
... As Lauder, Sari, Suwartha, and Tjahjono (2015) stated, campuses "have been conceptualized as 'small cities' in their quest to attain sustainability 2. LITERATURE REVIEW Thermal balance varies due to clothing, physical activity, and environmental parameters. In this context, environmental parameters are an array of geographical location (Mohajerani, Bakaric, & Jeffrey-Bailey, 2017;Robitu, Musy, Inard, & Groleau, 2006), meteorological situation (Chen & Ng, 2012), urban form (Andreou, 2013;Fuladlu, 2019Fuladlu, , 2020Fuladlu, Riza, & İlkan, 2018a, 2018bRobitu et al., 2006), surface materials (Andreou, 2013;Fuladlu et al., 2018a;Jamei, Rajagopalan, Seyedmahmoudian, & Jamei, 2016;Mohajerani et al., 2017;Robitu et al., 2006), amount of vegetation and watershed (Andreou, 2013;Jamei et al., 2016;Mohajerani et al., 2017;Robitu et al., 2006), and anthropogenic pollution (Fuladlu & Altan, 2021;Fuladlu et al., 2018a;Marsh & Grossa, 1996;Robitu et al., 2006). The COS's microclimate is a combined response to these environmental parameters. ...
Article
Open spaces—whether public, urban, or part of a campus—offer a variety of activities and opportunities to people. Therefore, open spaces should be considered a vital component of any built-up area and designed to meet the needs and address the comfort of potential users. Because of their presence in daily life and their preponderance of characteristics, open spaces have drawn the attention of many researchers, designers, and planners with varying perspectives. The current study takes a scientific approach to analyzing the environmental parameters of the Campus Outdoor Space (COS) in the case of the Eastern Mediterranean University (EMU). An extensive literature review supported the identification of seven important environmental parameters effective in the microscale analysis of a COS: geographical location, meteorological situation, urban form, surface materials, amount of vegetation and watershed, and anthropogenic pollution. Analysis of the environmental parameters called for a hybrid method that included a detailed field survey and the following set of simulations: sun-path, radiation, sky view factor, and turbulence analysis. The accuracy of the field survey directly contributed to the effectiveness of the simulations. Grasshopper® 3D software and Computational Fluid Dynamics were used to simulate the conditions of the EMU study area. The outcomes show that the spatial organization, building forms, and building orientation negatively affect the COS of EMU. In the Mediterranean climatic region of EMU, shade and flowing breezes greatly enhance comfort and usability of outdoor spaces from April to October. The massive form of buildings and minimal planning for effective building orientation to the sun increased heat storage capacity and neglected prevailing winds, resulting in flow separation and formation of eddies on the leeward side of buildings. These negatively influenced the microclimate, and thereby user comfort, at the core of the EMU’s main COS.
... Over the past decades, China has experienced rapid urbanization, which may further exacerbate the longterm trends of heat extremes under global warming (Hua et al., 2015;Lin et al., 2020;Luo & Lau, 2019b;Ren & Zhou, 2014). In particular, residents in cities and urban agglomerations are facing increasing threats of hot extremes (Luo & Lau, 2018;Ren & Zhou, 2014;Sun et al., 2014), which are closely related to urban development such as urban heat island (UHI) formation, urban land expansion, and land-use change (Fuladlu et al., 2018;Huang et al., 2019;Jiang et al., 2019;Oke, 1973;Zhao et al., 2018). Previous studies have shown that urbanization significantly intensifies regional climate warming in China (Feng et al., 2012;Sun et al., 2016;Zhou et al., 2004). ...
Article
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More than half of the total population in China are living in cities. Especially, the people in highly developed and spatially integrated city clusters, i.e., urban agglomerations (UAs), are facing increasing human-perceived heat stress that describes the combined effects of hot temperature, high humidity, and lowered surface wind speed. By analyzing multiple indicators over 20 major UAs across China, we demonstrate that summer heat stress has been significantly intensifying in nearly all UAs during 1971‒2014. This intensification is more profound in northern than southern regions and is especially stronger in more urbanized and densely populated areas (e.g., Beijing-Tianjin-Hebei and the Yangtze River Delta). Based on a dynamic classification of weather stations using time-varying land use/land cover maps, we find that urban core areas exhibit distinctly stronger increasing heat stress trends than their surrounding rural areas. On average, urbanization contributes to approximately one-quarter of the total increase in mean heat stress over urban core areas of UAs and nearly half of the total increase in extreme heat events. The urbanization effect is also dependent on the geographical region within China. Urbanization tends to have stronger intensifying effects on heat stress in UAs with higher population density in low-altitude areas, while it has a relatively weaker intensifying and even weakening effect in some arid and high-altitude regions. Moreover, as various heat stress metrics may yield different estimations of long-term trend and urbanization contribution, the particular choice of heat stress indicator is of critical importance for investigations on this subject matter.
... The average particulate air pollution levels in these cities were found to be 4-15-times higher than the WHO air quality guideline limit levels. Dense urban areas increase the risk of the two above-mentioned SLODs for the following main reasons: (1) reduced evaporation, transpiration, and shading, due to limited green areas and disadvantageous geometry; (2) increased surface temperatures with high thermal capacity and/or low albedo; and (3) increased air stagnation due to diminished wind speed [11][12][13][14][15], thus making every portion of the city (e.g., neighborhood) react/provide a different meso-climate to the people within it. ...
Article
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Citizens in dense built environments are susceptible to the simultaneous occurrence of Slow Onset Disaster (SLOD) events, being particularly prone to increasing temperatures and air pollution. Previous research works have assessed these events’ arousal separately and have identified when their intensity is critical. However, few have integrated their analysis, possibly limited by the quality and granularity of available data, the accessibility and distribution of sensors, and measurements not emulating the surroundings of a pedestrian. Thus, this work performed an outdoor meso-scale multi-hazard-based risk analysis to study the aggregated effects of the SLODs mentioned above. The study was carried out to narrow down the time-frames within 2019 in which these two events could have affected citizens’ health the most. A weighted fuzzy logic was applied to superimpose climatic (temperature, humidity, wind speed, and solar irradiance) and air quality (particulate matter, ozone, and ammonium) distress (true risk) on an hourly basis, allocated using set healthy and comfortable ranges for a specific dense urban climate context within Milan (Italy), processing data from Milano via Juvara station. The findings show that sensitive groups were at risk of high temperature and pollution separately during 26% and 29% of summer and mid-season hours, respectively; while multi-hazard risk would arise during 10.93% of summer and mid-season hours, concentrated mainly between 14:00 and 20:00.
... The increase in urban population and housing has increased the utilization of construction building materials inside the urban areas as well in the suburbs. As a result, the construction and building materials which have hard surface such as Fig. 1 Influence of UHI on the temperature of various residential areas [7] concrete and asphalt pavement are expanding and replacing natural surfaces and green areas [3,4]. This transformation, however, has severe negative impact on the existing thermal balance. ...
Article
The construction of concentrated infrastructures due to rapid urbanization has given rise to urban heat island (UHI) phenomenon which causes temperature of urban areas to significantly increase compared to its adjacent cooler rural areas. The absorption of heat in the form of solar radiation by infrastructures is the main contributor to UHI, which results in the rise in the ambient temperature at night. This has forced the construction industry to focus on thermal insulating building materials such as foamed concrete. Air voids in the matrix of foamed concrete allow it to reduce the thermal conductivity and dry density; however, due to its reduced density, foamed concrete is prone to microcracking which results in loss of strength. To counteract the development and propagation of microcracks, polypropylene (PP) fibres are used to reinforce the foamed concrete. Therefore, in this study, foamed concrete of density 1600 kg/m 3 was reinforced using PP fibres in three percentages, 0.20%, 0.25% and 0.30%. Thermal performance, in terms of thermal conductivity and surface temperature, was conducted as well as the compressive and tensile strength was determined. It was observed that the PP fibres not only enhanced the strength but also significantly lowered the thermal conductivity and absorbed less heat.
Article
Population growth and urbanization lead to urban heat island (UHI) phenomenon. Urbanization is occurring at a very high rate in the Surat city. Thus, the study of the urbanization impact on the UHI effect for the Surat city is performed in the present study through studying the impact of land use land cover on the land surface temperature of urban and sub-urban areas of the Surat city over the period May 1998 to May 2018. Also, these effects are compared with that of a nearby sub-urban taluka Kamrej, which showed that temperature in urban areas is more than that of the sub-urban areas. Aforesaid facts clearly showing the existence of the UHI effect in the Surat city. As urbanization contributes to climate change, its effects on rainfall are studied by comparing rainfall trends of urban and sub-urban areas of the Surat city and nearby sub-urban area Kamrej. Trend analysis showed that trend magnitude values are higher for the urban areas than sub-urban areas, indicating that UHI effect increases rainfall in urban areas. Hotspot analysis is also performed for the Surat city corresponding to May 2018 to recognize hot spots and cold spots. As the Surat city is highly urbanized, thus, hotspots are more than cold spots.
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Knowledge of the day-to-day dynamics of surface urban heat island (SUHI) as well as their underlying determinants is crucial to a better design of effective heat mitigation. However, there remains a lack of a globally comprehensive investigation of the responsiveness of SUHI variations to meteorological variables. Based on the MODIS LSTs and auxiliary data in 2017, here we investigated 10,000+ cities worldwide to reveal day-to-day SUHI intensity (SUHII) variations (termed as SUHIIdv) in response to meteorological variables using Google Earth Engine. We found that: (1) meteorological variables related to the thermal admittance, e.g., precipitation, specific humidity and soil moisture (represented by daily temperature range in rural area, DTRr), reveal a larger regulation on SUHIIdv than those related to the air conditions (e.g., wind speed and near-surface air temperature) over a global scale. (2) Meteorological regulations on SUHIIdv can differ greatly by background climates. The control of specific humidity on SUHIIdv is significantly strengthened in arid zones, while that of wind speed is weakened prominently in equatorial zones. SUHIIdv is more sensitive to soil moisture in cities with higher background temperatures. (3) All meteorological variables, except that related to soil moisture (DTRr), show larger impact on SUHIIdv with antecedent precipitation over the global scale. Precipitation is observed to mitigate the SUHIIdv globally, and such effects are even more pronounced in equatorial and arid zones. We consider that our findings should be helpful in enriching the knowledge of SUHI dynamics on multiple timescales.
Thesis
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More than half of the world’s population now lives in urban areas, and trends in rural-to-urban migration are expected to continue through the end of the century. Although cities create efficiencies that drive innovation and economic growth, they also alter the local surface energy balance, resulting in urban temperatures that can differ dramatically from surrounding areas. Here we introduce a global 1 km resolution data set of seasonal and diurnal anomalies in urban surface temperatures relative to their rural surroundings. We then use satellite-observable parameters in a simple model informed by the surface energy balance to understand the dominant drivers of present urban heating, the heat-related impacts of projected future urbanization, and the potential for policies to mitigate those damages. At present, urban populations live in areas with daytime surface summer temperatures that are 3.21 ∘C (−3.97, 9.24, 5th–95th percentiles) warmer than surrounding rural areas. If the structure of cities remains largely unchanged, city growth is projected to result in additional daytime summer surface temperature heat anomalies of 0.19 ∘C (−0.01, 0.47) in 2100—in addition to warming due to climate change. This is projected to raise the urban population living under extreme surface temperatures by approximately 20% compared to current distributions. However we also find a significant potential for mitigation: 82% of all urban areas have below average vegetation and/or surface albedo. Optimizing these would reduce urban daytime summer surface temperatures for the affected populations by an average of −0.81 ∘C (−2.55, −0.05).
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