Atlanta’s urban heat island under extreme heat conditions and potential mitigation strategies

2009 ◽  
Vol 52 (3) ◽  
pp. 639-668 ◽  
Author(s):  
Yan Zhou ◽  
J. Marshall Shepherd
Keyword(s):  
Urban Heat Island ◽  
Extreme Heat ◽  
Mitigation Strategies ◽  
Heat Island ◽  
Urban Heat

Observational evidence of urban heat island intensification during heatwaves in European cities

2021 ◽  
Author(s):  
Marco Possega ◽  
Leonardo Aragão ◽  
Paolo Ruggieri ◽  
Marco Antonio Santo ◽  
Silvana Di Sabatino
Keyword(s):  
Urban Heat Island ◽  
Rural Areas ◽  
Observational Evidence ◽  
Extreme Heat ◽  
Mitigation Strategies ◽  
Maximum Temperature ◽  
Daily Maximum ◽  
Heat Island ◽  
European Cities ◽  
Urban Heat

<p>Heatwaves (HWs) are extreme weather conditions characterized by persistent high temperatures with considerable impacts on society in terms of mortality, thermal stress and energy demand of the population. One of the most interesting aspects of HWs concerns the interaction with the phenomenon of urban heat island (UHI). The UHI is the tendency of urbanized areas to have warmer temperatures than the surrounding rural areas, mainly due to the thermal properties of materials forming urban environment and the heat produced by human activities. Some studies analyzed the behavior of UHI during periods of extreme heat, showing an amplification of the gradient of temperature between urban and rural areas in HW conditions, but the results are often limited to case studies with a single HW and/or a specific city. Other papers dealt with the same topic by examining events on various cities using outputs of global models, but with resolution insufficient to include in detail urban-scale processes and therefore to take into account specific properties of the cities investigated. The approach of this work consisted in providing observational evidence and extending the aforementioned results, studying the effect of HWs on UHI in about ten European cities with different characteristics (geography, topography, urban planning) through the analysis of daily maximum/minimum temperatures data measured by meteorological stations for the summers of period 2006-2019. In particular, the intensity of UHI was assessed through the computation of a Composite UHI Index (UHII), defined as the difference between averaged urban and non-urban values. The different behavior of UHII during HWs compared to "normal" summer days (NO) in selected European cities was investigated, detecting an intensification of index values regarding periods of extreme heat for the majority of examined locations. More specifically, the analysis of temporal evolution of UHII was conducted, revealing an average increase of this index during the occurrence of HW events. Moreover, a correlation between UHI index and maximum temperature anomalies was examined, and HW days appeared to exhibit a larger percentage of positive UHII with respect to NO days, showing also higher absolute values. This work provides an indication of how European urban areas respond to severe hot periods and could be useful to validate numerical model simulations for more detailed analysis, for example regarding mitigation strategies. Finally, the emergence of some outliers, namely cities whose UHI manifested a different reaction to HWs, may deserve dedicated studies in the future.</p>

scholarly journals Observational evidence of urban heat island intensification during heatwaves in European cities

2021 ◽  
Author(s):  
Marco Possega ◽  
Leonardo Aragão ◽  
Paolo Ruggieri ◽  
Marco Antonio Santo ◽  
Silvana Di Sabatino
Keyword(s):  
Urban Heat Island ◽  
Rural Areas ◽  
Heat Waves ◽  
Observational Evidence ◽  
Extreme Heat ◽  
Mitigation Strategies ◽  
Daily Maximum ◽  
Heat Island ◽  
European Cities ◽  
Urban Heat

<p>Heat waves (HWs) are extreme weather conditions characterized by persistent high temperatures with considerable impacts on society in terms of<br>mortality, thermal stress and energy demand of the population. One of the most interesting aspects of HWs concerns the interaction with the phenomenon<br>of urban heat island (UHI). The UHI is the tendency of urbanized areas to have warmer temperatures than the surrounding rural areas, mainly due to the thermal<br>properties of materials forming urban environment and the heat produced by human activities. Some studies analyzed the behavior of UHI during periods of<br>extreme heat, showing an amplification of the gradient of temperature between urban and rural areas in HW conditions, but results are often limited to case<br>studies with a single HW and/or a specific city. Other papers dealt with the same topic by examining events on various cities using outputs of global models,<br>but with resolution insufficient to include in detail urban-scale processes and therefore to take into account specific properties of the cities investigated. The<br>approach of this work consisted in providing observational evidence and extending the aforementioned results, studying the effect of HWs on UHI in 41 European cities<br>with different characteristics (geography, topography, urban planning) through the analysis of daily maximum / minimum temperatures data measured by<br>meteorological stations for the summers of period 2000-2019. In particular, the intensity of UHI was assessed through the computation of a Composite UHI Index<br>(UHII), defined as the difference between averaged urban and non-urban values. The different behavior of UHII during HWs compared to "normal" summer days<br>(NO) in selected European cities was investigated, detecting an intensification of index values regarding periods of extreme heat for the majority of examined<br>locations. More specifically, the analysis of temporal evolution of UHII was conducted, revealing an average increase of this index during the occurrence of<br>HW events due to higher urban than rural temperatures. This work provides an indication of how European urban areas respond to severe hot periods and could<br>be useful to validate numerical model simulations for more detailed analysis, for example regarding mitigation strategies. Finally, the emergence of some outliers,<br>namely cities whose UHI manifested a different reaction to HWs, may deserve dedicated studies in the future.</p><p> </p>

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

Water ◽  
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.

scholarly journals Mitigating the Urban Heat Island Effect in Megacity Tehran

2014 ◽  
Vol 2014 ◽  
pp. 1-19 ◽  
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.

scholarly journals Urban heat island intensity and its mitigation strategies in the fast-growing urban area

2020 ◽  
Vol 9 (1) ◽  
pp. 54-66 ◽  
Author(s):  
Shweta Jain ◽  
Srikanta Sannigrahi ◽  
Somnath Sen ◽  
Sandeep Bhatt ◽  
Suman Chakraborti ◽  
...  
Keyword(s):  
Urban Heat Island ◽  
Urban Area ◽  
Mitigation Strategies ◽  
Urban Heat Island Intensity ◽  
Heat Island ◽  
Fast Growing ◽  
Urban Heat

scholarly journals Investigation of Urban Air Temperature and Humidity Patterns during Extreme Heat Conditions Using Satellite-Derived Data

2015 ◽  
Vol 54 (11) ◽  
pp. 2245-2259 ◽  
Author(s):  
Leiqiu Hu ◽  
Andrew J. Monaghan ◽  
Nathaniel A. Brunsell
Keyword(s):  
Urban Heat Island ◽  
Air Temperature ◽  
Urban Land Use ◽  
Extreme Heat ◽  
Heat Island ◽  
Near Surface ◽  
Vegetation Fraction ◽  
Dewpoint Temperature ◽  
Temperature And Humidity ◽  
Urban Heat

AbstractExtreme heat is a leading cause of weather-related human mortality. The urban heat island (UHI) can magnify heat exposure in metropolitan areas. This study investigates the ability of a new MODIS-retrieved near-surface air temperature and humidity dataset to depict urban heat patterns over metropolitan Chicago, Illinois, during June–August 2003–13 under clear-sky conditions. A self-organizing mapping (SOM) technique is used to cluster air temperature data into six predominant patterns. The hottest heat patterns from the SOM analysis are compared with the 11-summer median conditions using the urban heat island curve (UHIC). The UHIC shows the relationship between air temperature (and dewpoint temperature) and urban land-use fraction. It is found that during these hottest events 1) the air temperature and dewpoint temperature over the study area increase most during nighttime, by at least 4 K relative to the median conditions; 2) the urban–rural temperature/humidity gradient is decreased as a result of larger temperature and humidity increases over the areas with greater vegetation fraction than over those with greater urban fraction; and 3) heat patterns grow more rapidly leading up to the events, followed by a slower return to normal conditions afterward. This research provides an alternate way to investigate the spatiotemporal characteristics of the UHI, using a satellite remote sensing perspective on air temperature and humidity. The technique has potential to be applied to cities globally and provides a climatological perspective on extreme heat that complements the many case studies of individual events.

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

2012 ◽  
Vol 51 (11) ◽  
pp. 1971-1979 ◽  
Author(s):  
Humberto Silva ◽  
Jay S. Golden
Keyword(s):  
Urban Heat Island ◽  
Mesoscale Model ◽  
Coupled Model ◽  
Mitigation Strategies ◽  
Turbulence Theory ◽  
Superposition Method ◽  
Heat Island ◽  
Lumped Model ◽  
Hourly Temperature ◽  
Urban Heat

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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