Spatial Superposition Method via Model Coupling for Urban Heat Island Albedo Mitigation Strategies

AbstractA spatial superposition design is presented that couples the fifth-generation Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model (MM5) with the National Center of Excellence (NCE) lumped urban thermal model for application to the city of Phoenix, Arizona. This technique utilizes an approach similar to Reynolds decomposition from turbulence theory. The presented decomposition takes the NCE model prediction from a mitigated strategy as the mean temperature and the difference between the NCE and MM5 predictions without mitigation strategy as the perturbed temperature. The goal of this coupled model is to provide spatial variability when simulating mitigation strategies for the urban heat island effect, as compared with the spatially invariant lumped model. A validation analysis was performed incorporating a maximum 35% change from the baseline albedo value for the urban environment. It is shown that the coupled model differs by up to 0.39°C with comparable average surface temperature predictions from MM5. The coupled model was also used to perform analysis of three different albedo-driven spatial mitigation schemes. This resulted in the identification that having a lesser number of mitigated points on a square urban grid in Phoenix with the same average albedo leads to a greater reduction in average hourly temperature.

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Mitigation measures for urban heat island and their impact on pedestrian thermal comfort

Journal of Physics Conference Series ◽

10.1088/1742-6596/2069/1/012058 ◽

2021 ◽

Vol 2069 (1) ◽

pp. 012058

Author(s):

A Kubilay ◽

D Strebel ◽

D Derome ◽

J Carmeliet

Keyword(s):

Thermal Comfort ◽

Urban Heat Island ◽

Coupled Model ◽

Mitigation Strategies ◽

Mitigation Measures ◽

Heat Island ◽

Heat And Moisture Transport ◽

Urban Heat ◽

Urban Square ◽

Heat And Moisture

Abstract A multiscale coupled model is presented that allows for the detailed analysis of the local impact of urban heat island mitigation measures. The model uses coupled computational fluid dynamics (CFD) simulations with unsteady heat and moisture transport (HAM) in porous urban materials in order to take into account the dynamic heat and moisture storage in the built environment. A realistic case study is performed for a public urban square in the City of Zurich during heat wave conditions. The impacts of two different mitigation strategies, i.e. adding artificial wetting of pavements and adding vegetation, on pedestrian thermal comfort are evaluated and compared with the existing situation. The results show an improvement in thermal comfort in both conditions. The improvement resulting from the addition of trees is larger and lasts longer due to shadowing effects, even though a reduced ventilation and an increased relative humidity by trees have an adverse effect on the thermal comfort.

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An analysis of urban heat island impact toward increasing of afternoon thunderstorm frequency in Taipei, Taiwan

10.5194/egusphere-egu21-10522 ◽

2021 ◽

Author(s):

Siti Talitha Rachma ◽

Yuan-Chien Lin

Keyword(s):

Urban Heat Island ◽

Empirical Orthogonal Function ◽

Precipitation Pattern ◽

Heat Island ◽

Hilbert Huang Transform ◽

Orthogonal Function ◽

Hourly Temperature ◽

Taipei City ◽

The Future ◽

Urban Heat

Each year, average of Earth&#8217;s temperature rises and the urbanized cities, are warming at a significant rate than the surrounding rural areas. This phenomenon is called Urban Heat Island (UHI). UHI is a consequence of human activities in urban area and it has possibilities to impact weather and climate on regional or global scale. Precipitation is one of the basic hydro-meteorological phenomena that could be affected by UHI trend with thunderstorm as a part of precipitation. As the UHI level rises from year to year, the pattern of precipitation could change. However, this issue is still underdeveloped, thus, this work tries to comprehensively understand the hydrological response to UHI.&#160;This research selects Taipei city as the study area and explores the connection between UHI and precipitation pattern&#8217;s change. The data used here are hourly temperature and precipitation data collected from 21 Taipei weather stations collected from Central Weather Bureau (CWB) Taiwan. In order to reveal specific details and trend of non-linear relation from both time domain and frequency, Hilbert-Huang Transform (HHT) is adopted in this study. The HHT results are compared between each station. Later, empirical orthogonal function (EOF) also being used to extract main spatial pattern of precipitation in Taipei city.&#160;The results show that the urbanization in Taipei city contribute to increasing trend of 0.5 &#8211; 1 oC in daily UHI and also increase of 27% in the afternoon thunderstorm frequency for this past 20 years. The increase of thunderstorm would result into a bigger rain water flow to the river and a fewer time for it to percolate to the ground. If there are more thunderstorms in the future, it is possible the phenomenon could lead to the lack of groundwater discharge and depletion of groundwater reserve. This result could be utilized in the future to understand more about UHI mitigation and thunderstorm in Taipei.&#160;Keywords: urban heat island, thunderstorm, Hilbert-Huang Transform, empirical orthogonal function

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Green Infrastructure as an Urban Heat Island Mitigation Strategy—A Review

Water ◽

10.3390/w12123577 ◽

2020 ◽

Vol 12 (12) ◽

pp. 3577

Author(s):

Fatma Balany ◽

Anne WM Ng ◽

Nitin Muttil ◽

Shobha Muthukumaran ◽

Man Sing Wong

Keyword(s):

Thermal Comfort ◽

Urban Heat Island ◽

Green Infrastructure ◽

Mitigation Strategies ◽

Heat Island ◽

Recent Past ◽

Simulation Tools ◽

Human Thermal Comfort ◽

Different Types ◽

Urban Heat

Research on urban heat mitigation has been growing in recent years with many of the studies focusing on green infrastructure (GI) as a strategy to mitigate the adverse effects of an urban heat island (UHI). This paper aims at presenting a review of the range of findings from GI research for urban heat mitigation through a review of scientific articles published during the years 2009–2020. This research includes a review of the different types of GI and its contribution for urban heat mitigation and human thermal comfort. In addition to analysing different mitigation strategies, numerical simulation tools that are commonly used are also reviewed. It is seen that ENVI-met is one of the modelling tools that is considered as a reliable to simulate different mitigation strategies and hence has been widely used in the recent past. Considering its popularity in urban microclimate studies, this article also provides a review of ENVI-met simulation results that were reported in the reviewed papers. It was observed that the majority of the research was conducted on a limited spatial scale and focused on temperature and human thermal comfort.

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Mitigating the Urban Heat Island Effect in Megacity Tehran

Advances in Meteorology ◽

10.1155/2014/547974 ◽

2014 ◽

Vol 2014 ◽

pp. 1-19 ◽

Cited By ~ 35

Author(s):

Sahar Sodoudi ◽

Parisa Shahmohamadi ◽

Ken Vollack ◽

Ulrich Cubasch ◽

A. I. Che-Ani

Keyword(s):

Urban Heat Island ◽

Rural Areas ◽

Heat Waves ◽

Mitigation Strategies ◽

Cooling Effect ◽

Heat Island ◽

Microscale Model ◽

Negative Effect ◽

Urban Heat ◽

Surrounding Areas

Cities demonstrate higher nocturnal temperatures than surrounding rural areas, which is called “urban heat island” (UHI) effect. Climate change projections also indicate increase in the frequency and intensity of heat waves, which will intensify the UHI effect. As megacity Tehran is affected by severe heatwaves in summer, this study investigates its UHI characteristics and suggests some feasible mitigation strategies in order to reduce the air temperature and save energy. Temperature monitoring in Tehran shows clear evidence of the occurrence of the UHI effect, with a peak in July, where the urban area is circa 6 K warmer than the surrounding areas. The mobile measurements show a park cool island of 6-7 K in 2 central parks, which is also confirmed by satellite images. The effectiveness of three UHI mitigation strategies high albedo material (HAM), greenery on the surface and on the roofs (VEG), and a combination of them (HYBRID) has been studied using simulation with the microscale model ENVI-met. All three strategies show higher cooling effect in the daytime. The average nocturnal cooling effect of VEG and HYBRID (0.92, 1.10 K) is much higher than HAM (0.16 K), although high-density trees show a negative effect on nocturnal cooling.

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