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![Figure 2. Land surface temperature of Hangzhou in 1991, 2000 and 2007 [8].](profile/Dhc-Chow/publication/273025325/figure/fig13/AS:329975724036097@1455683751358/Land-surface-temperature-of-Hangzhou-in-1991-2000-and-2007-8_Q320.jpg)
There are many indications that Urban Heat Island (UHI) is a significant contributor to the increased emission of greenhouse
gases due to the increase in energy consumption for cooling during summer. Hangzhou is currently the second hottest city in
China, and this paper investigates how the West Lake and the Xixi Wetland areas in the city act as pa...
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... the capital of Zhejiang Province, lies 180 km south- west of Shanghai (Figure 1). It has a total area of 16 596 km 2 and forms part of Yangtze River Delta region, one of the most dy- namically developed, densely populated and concentrated urba- nized areas situated on the east coast of China [5]. ...
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... the cooler air from the Qiantang River also cannot be blown to the urban area either, because the buildings on the northeast side of the river are highest and block the cool wind into the urban area. Figure 10a and b shows the case where the wind direction changes to southwest and the comparison with the prime case. It is clear that the shape of UHI changes. ...
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... the gap between buildings also relates to another variable, the SVF, which is an important indicator of the magni- tude of urbanization of a city. Figure 11 shows that an area with low SVF can be normally recognized as urban area where UHI effect is significant. Nevertheless, the impact of SVF on UHI is quite complicated. ...
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... reference weather data file of Hangzhou is downloaded from Energy Plus webpage. Figure 12 shows the appearance of the urban building model designed in Ecotect. Table 2 displays the material descriptions of the simulated urban building and Table 3 lists the average monthly temperature value in reference and the modified weather data files. ...
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... this case study, cooling demand of urban building in summer is simulated to evaluate the impact of the temperature increase of 0.58C on the cooling energy consumption of the designed urban building, as Figure 13 illustrates. If the ambient temperature increases 0.58C, the total cooling demand of the urban building is 41 KWh=m 2 , which is 10.8% higher than the value that is based on the reference weather data file. ...
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Citations
... For example, Ryu and Baik (2013) demonstrated that urban breeze could transport high-reactivity precursors and O 3 -rich air to Seoul, leading to about 15-ppb increase in O 3 concentrations. Some research on the impacts of land cover and their distributions to UHI in HMA has been carried out (Shen et al., 2013;Chen et al., 2014;Li et al., 2015). None of the previous work, however, focused on the role of UHIC on O 3 in HMA. ...
Impacts of coastal local circulations and their interactions on ozone (O3) in Hangzhou on 5 June 2018 with relatively low temperatures were investigated using surface observations and three-dimensional air quality simulations. Local circulations and their interactions were primary causes of the episode instead of high temperatures. Northwesterly land breeze on the previous day transported O3 to sea, and sea breeze (SB) on the episode day blew pollution back to land. Inland penetration (east to west) of the combined SB front (SBF) was accelerated by urban heat island (UHI) induced easterly flow over coast and slowed by its westerly flow and surface roughness over inland urban areas. O3 accumulation at surface and in the elevated air over city was caused by mountain barrier effect and venting process. Subsidence heating associated with valley circulation accelerated UHI circulation (UHIC) before 1400 LT, indirectly strengthening the SB circulation (SBC). The UHIC and valley circulation decoupled with SBC at noon and in the late afternoon, respectively, leading to a stronger SBC. The stronger SBC brought additional O3 (>20 ppb) to further inland area, to elevated air with updrafts in SB head, and to nocturnal stable boundary layer and residual layer with its upper-level offshore flow.
... Later, scholars uncovered several types of UHI, such as boundary-layer heat islands and surface urban heat islands (SUHI) (Oke et al., 2017). The UHI can lead to more energy consumption in the summer due to rising cooling needs (Shen et al., 2013;Wilson, 2013;Almeida et al., 2021;Singh & Sharston, 2022). Combined with the trend of frequent heatwaves, the UHI exposes vulnerable people (e.g., elders, patients, and children) to health risk (Cai et al., 2019;Zhao et al., 2018;Van et al., 2017;Zhang et al., 2019), increasing their morbidity and mortality (Rydin et al., 2012;Zhang et al., 2019;Mora et al., 2017;Yang et al., 2019). ...
As most cities are located around or near waterbodies, it is essential to assess the thermal effect of these waterbodies. This research focuses on 34 Chinese megacities as case studies to examine the spatial relationship between city-water layout and the thermal effect of waterbodies. Landsat-8 remote-sensing images acquired around noontime in summer were used to retrieve land surface temperatures (LST) and classify land cover. The results show that there are three types of city-water layout. For most cities, waterbodies have a cooling effect, and their mean cooling distance (∆Lmax) ranges from 431 m to 1350 m, with the maximum temperature difference (∆Tmax) ranging from-2.21 ℃ to 7.83 ℃. The cooling effect of waterbodies is also influenced by their spatial distribution, size, location, and background climate regions. The larger the percentage or area of waterbodies in a city, the shorter ∆Lmax and the bigger ∆Tmax. Waterbodies have the longest ∆Lmax and the smallest ∆Tmax when they are dispersed within the city, whereas they have the shortest ∆Lmax and the largest ∆Tmax when they are flowing through the city. The results suggest that the thermal effects of waterbodies should be seriously considered by urban planners to improve the urban microclimate. Journal of Environmental Management has accepted this paper. 2
... The Yangtze River Delta (YRD) is one of the regions with the highest degree of urbanization after the Reform and Opening-up in China and is also the location of major cities with significant UHI effect. Located on estuary and coast, it is vulnerable to climate change, so it has attracted a large number of similar studies (Shen et al., 2013;Li et al., 2020). ...
It is not deep enough that the theoretical and empirical analysis of economic drivers on the urban heat island (UHI) effect have been researched. Consequently, the study of economic drivers of the UHI effect is not only conducive to the governance of the UHI problem but also conducive to deepening the study of related issues in the economic field. The Yangtze River Delta (YRD) region of China has developed economic status and the special geography of estuaries and coasts. Therefore, 26 central cities in the YRD region are selected as research samples, and the period from 2003 to 2017 is taken as the observation period. The Spatio-temporal variability of UHI intensity caused by industrialization and urbanization is analyzed by using MODIS land surface temperature (LST) data and related yearbook data. The conclusions are as follows:(1) The UHI intensity of cities in the YRD region is significant and fluctuates to a certain extent. (2) Empirical analysis shows that the agglomeration of single economic factors in the process of industrialization and urbanization does correlate with the UHI intensity in the YRD region, but the correlation may show a downward trend due to the influence of exogenous factors suc0h as physical geography. (3) In terms of economic drivers, the combination of multiple factors can produce a greater UHI intensity. The model of their impacts on UHI intensity is increasingly-changed, which is from a model of Fixed Asset Investment and the Motor Vehicle Population as dominant factors to a model of multiple overlapping economic factors, and the latter has a greater impact.
... By reviewing the impact of UHI on building energy, UHI could lead to a 19% increase in the median building cooling energy consumption [26]. For typical urban buildings, the simulation shows that if the outdoor air temperature increases by 0.5 • C, the cooling demand increases by 10.8% [27]. UGI alleviates UHIs through canopy shading and evapotranspiration [28]. ...
Urban green infrastructures (UGIs) play an essential role in reducing urban building energy consumption by cooling surrounding areas and shielding buildings from direct solar radiation heat gain. Although the energy-saving effect of UGIs is widely agreed upon, there is a lack of systematic knowledge about how UGI morphology affects urban building energy consumption. Consequently, an effective method to design UGI morphology to reduce urban building energy consumption in urban design is not available. A grading system was proposed to evaluate the strength of evidence for the findings and conclusions in studies that pertain to the cooling and energy-saving effects of UGI. The evidence-based literature review found that strategically designing the morphology of UGI, including its size, shape, location, connectivity, spatial pattern, and configuration, can effectively reduce the air temperature surrounding the UGI area and building energy demand. This study formulated a morphological design framework for UGI as part of the urban design process to reduce urban building energy consumption. Based on the evidence-based answers to the key questions in the framework, design strategies are provided as visual charts and technical principles. The study includes an urban design case in Nanjing, China, which applied this framework to achieve the goal of urban energy savings.
... Previous studies have focused on the impact of urban geometry on outdoor thermal comfort, such as the aspect ratio (Ali-Toudert & Mayer, 2006;Emmanuel et al., 2007), SVF (Ali-Toudert & Mayer, 2006;Andrade & Alcoforado, 2008;Kakon et al., 2009;Krüger et al., 2011;Shen et al., 2013), street orientation (Ali-Toudert & Mayer, 2007;Emmanuel et al., 2007;Fahmy & Sharples, 2009;Hedquist & Brazel, 2014;Ketterer & Matzarakis, 2014), building density (Hedquist & Brazel, 2014;Perini & Magliocco, 2014;Shen et al., 2013), and building forms (Fig. 9 and Table B1). The interaction between aspect ratio, orientation, and vegetation inside a street canyon is required to determine the level of thermal stress at the pedestrian level (Yahia & Johansson, 2013). ...
... Previous studies have focused on the impact of urban geometry on outdoor thermal comfort, such as the aspect ratio (Ali-Toudert & Mayer, 2006;Emmanuel et al., 2007), SVF (Ali-Toudert & Mayer, 2006;Andrade & Alcoforado, 2008;Kakon et al., 2009;Krüger et al., 2011;Shen et al., 2013), street orientation (Ali-Toudert & Mayer, 2007;Emmanuel et al., 2007;Fahmy & Sharples, 2009;Hedquist & Brazel, 2014;Ketterer & Matzarakis, 2014), building density (Hedquist & Brazel, 2014;Perini & Magliocco, 2014;Shen et al., 2013), and building forms (Fig. 9 and Table B1). The interaction between aspect ratio, orientation, and vegetation inside a street canyon is required to determine the level of thermal stress at the pedestrian level (Yahia & Johansson, 2013). ...
... Apart from aspect ratios in street canyons, building structure could influence outdoor thermal comfort. Building arrangements, such as gaps between buildings, affect urban ventilation Du et al., 2019;Shen et al., 2013). For detached buildings, street orientation and aspect ratio had a weak influence on outdoor thermal comfort, whereas vegetation had a stronger influence (Yahia & Johansson, 2013). ...
Computer simulation programs have been used since 2006 for analyzing outdoor human thermal environments. This study reviewed 130 peer-reviewed papers published during 2006–2019, which investigated outdoor thermal comfort using computer simulations. Most studies were conducted in the Northern Hemisphere and the temperate oceanic climate during summer. The widely used computer simulation program and thermal indices were the ENVI-met and physiological equivalent temperature, respectively. To validate the simulation results for urban planning and design, 61% of the studies compared the simulation results with observation data. Moreover, 45% and 27% of the studies validated the simulation results with measured air temperature and mean radiant temperature, respectively. Thermal indices were validated in 12 studies. Mitigation strategies to improve urban outdoor thermal environments can be analyzed in three categories: the effects of urban geometry, urban vegetation, and surface materials. To address the impact of climate change, future studies should consider the future urban structural plan and design scenarios, such as building heights, street orientations, and surface types. Moreover, further studies can adopt multi-scale approaches (e.g. global scale, mesoscale, and micro-scale). This study will help researchers select a suitable numerical simulation program according to their requirements.
... Increased UHI effects impact waterstressed regions as residents demand more water for outdoor uses (Gober et al., 2012). Higher temperatures are associated with increased energy use for air-conditioning and refrigeration (Miner et al., 2016;Shen et al., 2013) and lead to higher rates of mechanical equipment breakdown (Miner et al., 2016). ...
... Increased UHI effects impact waterstressed regions as residents demand more water for outdoor uses (Gober et al., 2012). Higher temperatures are associated with increased energy use for air-conditioning and refrigeration (Miner et al., 2016;Shen et al., 2013) and lead to higher rates of mechanical equipment breakdown (Miner et al., 2016). ...
Rapid unplanned urbanization has led to a deterioration in green cover in Indian cities and an increase in urban temperatures due to the urban heat island (UHI) effect. With India’s urban population set to double from 400 million in 2011 to 800 million by 2050, it becomes critical to understand the role of urban green spaces (UGS) in mitigating the UHI. In this study, we have used high-resolution Landsat and Google Earth data and integrated it with spatial statistical analysis to quantify the cooling effects provided by UGS beyond their boundaries. We analyzed cooling effects at the level of individual UGS for 262 UGS in the megacity of Bengaluru, India. Our results showed that the average UGS provided local cooling effects till points 347 m (95% CI: 318 m to 376 m) beyond its boundary. The average UGS was 2.23 °C (95% CI: 2.13 °C to 2.33 °C) cooler than the point where it ceased to provide cooling effects. Cooling effects reduced with distance from the UGS, and were impacted by the greenness, size, and shape of the UGS. The findings of this study are important in the context of India’s Smart Cities Mission that has been criticized for an inadequate focus on urban greening. Our study addresses a concern that most previous studies have used a small sample of UGS for their analysis. To the best of our knowledge, this is the first study to quantify the role of UGS in localized surface temperature reduction for a large Indian city.
... Existen varias maneras de abordar el estudio de ICU, las variables más utilizadas en este tipo de estudios son la temperatura del aire y el de los materiales presentes en la superficie (Castán Broto & Bulkeley, 2013;Du et al. 2016;Fan et al. 2016;Offerle et al. 2007;T. Oke, 2002;Shen et al. 2013). Además, es común el uso de un enfoque cuantitativo, en el que se desarrollan modelos físicos y de correlación debido a las propiedades físicas de los diversos tipos de superficies urbanas son factores importantes que determinan la temperatura de la superficie de la tierra en las áreas urbanas. ...
La presente investigación estudia la influencia del cambio de las coberturas de la tierra en el comportamiento de la intensidad y distribución espacial de la Isla de Calor Urbano (ICU) en la Ciudad de Heredia, entre los años 1985 al 2019. Con el propósito de establecer una serie lineamientos a ser considerados en la planificación de áreas urbanas sostenibles, así como para establecer planes de intervención del diseño urbano, que involucre reverdecer y arborizar la ciudad para regular la temperatura de la superficie.
La investigación analiza la morfología urbana, identifica y determina la evolución de las diferentes coberturas de la tierra mediante la estimación del índice de disturbio y como estas transformaciones influencian el aumento de la temperatura de la superficie terrestre entre el núcleo y los sectores periféricos de la ciudad, y que definen el fenómeno de la ICU.
Se asocia para cada cobertura su patrón de comportamiento térmico durante el período temporal y ámbito espacial; con tal de definir la magnitud e intensidad de la ICU. Para esto se utilizan metodologías de análisis espacial y geoestadísticos avanzados. También se construyen escenarios posibles y se identifican la dinámica de los actores, así como su percepción sobre temas asociados al incremento de la temperatura de la ciudad, el cambio climático y la gestión territorial.
URL: http://hdl.handle.net/10669/82280
... Artificial or natural wetlands that are located inside or around the city fulfill many esthetic and functional functions. In addition to their effects on urban microclimate, they fulfill many economic, ecological, and esthetic functions such as visually creating beautiful sceneries, providing an ecosystem for many animals, creating oxygen, allowing for the functioning of many sectors such as fishing and transportation, and serving as a recreational area (Eppinka et al. 2004;Shen et al. 2013;Zhang et al. 2016). The effects of wetlands on urban microclimate are generally evapotranspiration and heat storage characteristics (Nakayama and Fujita 2010). ...
With the rapid rise in population density in urban areas, there has also been an increase in research on quality of life and the effects of green space on health and comfort in densely populated cities. A critical part of improving the quality of life in urban areas is the reduction of urban heat island effect, especially in hot climate cities, and the reduction of adverse effects of winter in cold climates. Urban planning and landscape design strategies can have a great impact on urban microclimates, thereby providing relief from the harsh effects of climate change. Studies reveal that the cultivation of wetlands and open green spaces can have a direct impact on microclimate and comfort in densely populated areas. Erzurum is under the cold stress of the decreasing temperature in winter and continues to experience extreme temperatures in summer. This study is focused on the effects of urban design and landscape architectural interventions in the city of Erzurum. For this purpose, meteorological stations were placed in intensive construction areas of the urban city center, in wetland areas, and in the forested area of Ata Botanical Park in the city center. Three stations, dense green areas (1), temporary wetlands (2), and urban city center areas (3), were selected as urban area use types. Meteorological data were collected during March–April when the wetlands were full due to heavier periods of rain, and during July–August, the hottest months in the city. Thermal comfort values have been analyzed for different areas using RayMan soft model. The average value of Physiologically Equivalent Temperature (PET) recorded in March–April was 3.5 °C in the city center, 2.8 °C in the dense green area, and − 0.3 °C around the temporary wetland area. In July and August, the average value of PET in the city center was 24.9 °C, 23.0 °C in dense green areas, and 21.2 °C around the wetland area. In cold cities, it was found that the water surfaces, which positively contribute to thermal comfort in summer, increased the cold stress in winter. It was determined that dense green areas function as balancing factors for thermal comfort of the city both for summer and winter seasons and they contributed positively in all conditions. As a result of this study, more accurate decisions can be made for future urban planning efforts by considering the effects of different environmental conditions on microclimates in the city, especially where this consideration can be applied to urban design and development, urban revitalization efforts, or when designing new settlements.
... [24,45]. UHI mitigation strategies have also been studied, including park induced cool islands [18,37]; passive cooling systems [52,53]; urban canyon orientation and aspect ratio [33]; and material properties [63]. It has been validated against field measurements [59], showing that it can reasonably simulate air T, as well as building surface radiative T and energy balance components [68]. ...
An obstacle to the modeling of strategies to mitigate extreme urban temperatures is frequently the lack of on-site meteorological data. The current study thus reports on a method that used the Weather Research and Forecasting (WRF) model to generate inputs for the ENVI-met model to produce building-scale canyon temperatures within a 300 m square near downtown San Jose. A land use distribution was generated for WRF by a WUDAPT classification, and the days of inter-est were the then hottest day in California history and a typical summer day. The source of met-eorological data for ENVI-met, run with a 1.5 m cubic grid, was either an urbanized version of WRF; its default version; or observations at the closest NWS site. All WRF simulations were run on a 1 km grid, and output at its grid closest to the study area provided ENVI-met with lateral boundary conditions. The mitigation strategy was comprised of three parts, which either in-creased vegetation, rooftop albedo, or architectural shade elements. Results showed all strategies with only negligible impacts on ENVI-met nighttime 1 m level temperatures. Increased vegeta-tion, however, was the most effective daytime strategy on both days, as it effected the largest area. The maximum vegetative cooling on the extreme and average days was −3.5 and −3.3 °C, respectively. While increased rooftop albedos produced near negligible impacts, increased architectural shading produced corresponding values of −1.6 and −1.7 °C, respectively.
