Integrated impacts of tree planting and aspect ratios on thermal environment in street canyons by scaled outdoor experiments

Chen, Taihan; Yang, Hongyu; Chen, Guanwen; Lam, Cho Kwong Charlie; Hang, Jian; Wang, Xuemei; Liu, Yonglin; Ling, Hong

doi:10.1016/j.scitotenv.2020.142920

Cited by 71 publications

(22 citation statements)

References 97 publications

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“…The outcome of a small-scale outdoor experimentally developed model in China proved the same finding as that found in this study, as small-canopied street canyons, at the pedestrian level, elevate the temperature range, when compared to the use of large canopy sizes. Additionally, studies found that single-row big and tall trees can improve the environment [25,54]; this finding aligns with our finding in the base case/existing scenario, where big trees and tall palms exist within the considered wide street canyon. Sodoudi et al have pointed out that the mean cooling response of small canopy trees is less than that of large canopy trees, across different urban configurations and temporal responses.…”

Section: Discussionsupporting

confidence: 91%

“…Through the simulation of nine design patterns, we presented results that demonstrated that, in wide street canyons, the addition of trees generally produces an enhanced cooling capacity, contingent on: (1) The percentage of tree coverage, depending on the canopy size; (2) the spacing between trees; and (3) their arrangement [16,24,25,54,55]. However, when low albedo surfaces exceed 30%, reflective or light-colored pavements are recommended in the first place, as the surface and ambient temperature can be decreased [30] In this case, large spherical evergreen trees with a canopy coverage of 25 m [55] are recommended, considering that no overlap exists and the spacing between trees is sufficient to allow for air flow and the saturated vapor to flow around and between the trees.…”

Section: Discussionmentioning

confidence: 99%

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Solar Irradiance Reduction Using Optimized Green Infrastructure in Arid Hot Regions: A Case Study in El-Nozha District, Cairo, Egypt

2021

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In the Middle East and North Africa (MENA) region, studies focused on the relationship between urban planning practice and climatology are still lacking, despite the fact that the latter has nearly three decades of literature in the region and the former has much more. However, such an unfounded relationship that would consider urban sustainability measures is a serious challenge, especially considering the effects of climate change. The Greater Cairo Region (GCR) has recently witnessed numerous serious urban vehicular network re-development, leaving the city less green and in need of strategically re-thinking the plan regarding, and the role of, green infrastructure. Therefore, this study focuses on approaches to the optimization of the urban green infrastructure, in order to reduce solar irradiance in the city and, thus, its effects on the urban climatology. This is carried out by studying one of the East Cairo neighborhoods, named El-Nozha district, as a representative case of the most impacted neighborhoods. In an attempt to quantify these effects, using parametric simulation, the Air Temperature (Ta), Mean Radiant Temperature (Tmrt), Relative Humidity (RH), and Physiological Equivalent Temperature (PET) parameters were calculated before and after introducing urban trees, acting as green infrastructure types that mitigate climate change and the Urban Heat Island (UHI) effect. Our results indicate that an optimized percentage, spacing, location, and arrangement of urban tree canopies can reduce the irradiance flux at the ground surface, having positive implications in terms of mitigating the urban heat island effect.

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Section: Discussionsupporting

confidence: 91%

Section: Discussionmentioning

confidence: 99%

Solar Irradiance Reduction Using Optimized Green Infrastructure in Arid Hot Regions: A Case Study in El-Nozha District, Cairo, Egypt

2021

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“…In order to mitigate the negative effects of UHI, especially during HWs, numerous strategies have been proposed, such as using permeable pavements [31][32][33] and reflective materials [34,35], increasing vegetation cover [36][37][38][39][40][41][42] and so on. Susca et al [43] evaluated the effectiveness of using vegetation for UHI mitigation in New York City and reported a positive impact since vegetation effectively reduced the building cooling/heating load and the consequent building energy consumption.…”

Section: Introductionmentioning

confidence: 99%

Urban Heat Island and Its Interaction with Heatwaves: A Review of Studies on Mesoscale

et al. 2021

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With rapid urbanization, population growth and anthropogenic activities, an increasing number of major cities across the globe are facing severe urban heat islands (UHI). UHI can cause complex impacts on the urban environment and human health, and it may bring more severe effects under heatwave (HW) conditions. In this paper, a holistic review is conducted to articulate the findings of the synergies between UHI and HW and corresponding mitigation measures proposed by the research community. It is worth pointing out that most studies show that urban areas are more vulnerable than rural areas during HWs, but the opposite is also observed in some studies. Changes in urban energy budget and major drivers are discussed and compared to explain such discrepancies. Recent studies also indicate that increasing albedo, vegetation fraction and irrigation can lower the urban temperature during HWs. Research gaps in this topic necessitate more studies concerning vulnerable cities in developing countries. Moreover, multidisciplinary studies considering factors such as UHI, HW, human comfort, pollution dispersion and the efficacy of mitigation measures should be conducted to provide more accurate and explicit guidance to urban planners and policymakers.

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“…Another approach is numerical modeling, in which numerical simulations are used to study the impact of changes in the MOE caused by urbanization on the meteorological observational elements (Zhang et al, 2002(Zhang et al, , 2016Liu and Zhou, 2007;Yang et al, 2016;Chen, 2021;Chen G. et al, 2021;Yu et al, 2021). The simulations include physical equations and the laws of atmospheric radiation related to energy and mass and therefore explain the changes in terms of the mechanism of influence.…”

Section: Drivers Of the Spatial Morphology Of The Moe On Urbanization Bias In Sat Seriesmentioning

confidence: 99%

“…FAR and SVF are two important parameters for characterizing the geometry, density and heat balance of urban areas, in addition to generating and controlling the heat island effect (Svensson, 2004;Chen et al, 2020;Chen G. et al, 2021). The BHWR and VV2BV are two important indicators for characterizing the microscopic three-dimensional morphology and play key roles in radiation balance and outdoor thermal environment studies (Shashua and Hoffman, 2000;Chen, 2021).…”

Section: Characterization Indexes Of Three-dimensional Morphology Of the Moementioning

confidence: 99%

Influence of Changes in Meteorological Observational Environment on Urbanization Bias in Surface Air Temperature: A Review

Tao

Yang

Sun³

et al. 2022

Front. Clim.

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It is important to quantify changes in the local meteorological observational environment (MOE) around weather stations if we are to obtain accurate assessments of the regional warming of the surface air temperature (SAT) in relation to urbanization bias. Current studies often use two-dimensional parameters (e.g., the land surface temperature, land use/land cover and the normalized difference vegetation index) to characterize the local MOE. Most of the existing models of the relationship between urbanization bias in SAT series and MOE parameters are linear regression models, which ignore the non-linear driving effect of MOE changes on SAT series. By contrast, there is a lack of three-dimensional parameters in the characterization of the morphological features of the MOE. Changes in the MOE related to urbanization lead to uncertainties in the contribution of SAT series on different scales and we need to introduce vertical structure indexes to enrich the three-dimensional spatial morphology of MOE parameters. The non-linear response of urbanization bias in SAT series to three-dimensional changes in the MOE and its scale dependence should be explored by coupling computational fluid dynamics model simulations with machine learning.

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Integrated impacts of tree planting and aspect ratios on thermal environment in street canyons by scaled outdoor experiments

Cited by 71 publications

References 97 publications

Solar Irradiance Reduction Using Optimized Green Infrastructure in Arid Hot Regions: A Case Study in El-Nozha District, Cairo, Egypt

Solar Irradiance Reduction Using Optimized Green Infrastructure in Arid Hot Regions: A Case Study in El-Nozha District, Cairo, Egypt

Urban Heat Island and Its Interaction with Heatwaves: A Review of Studies on Mesoscale

Influence of Changes in Meteorological Observational Environment on Urbanization Bias in Surface Air Temperature: A Review

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