Green and cool roofs to mitigate urban heat island effects in the Chicago metropolitan area: evaluation with a regional climate model
The effects of urban heat islands (UHIs) have a substantial bearing on the sustainability of cities and environs. This paper examines the efficacy of green and cool roofs as potential UHI mitigation strategies to make cities more resilient against UHI. We have employed the urbanized version of the W...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
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IOP Publishing
2016-01-01
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| Series: | Environmental Research Letters |
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| Online Access: | https://doi.org/10.1088/1748-9326/11/6/064004 |
| _version_ | 1827871141392285696 |
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| author | A Sharma P Conry H J S Fernando Alan F Hamlet J J Hellmann F Chen |
| author_facet | A Sharma P Conry H J S Fernando Alan F Hamlet J J Hellmann F Chen |
| author_sort | A Sharma |
| collection | DOAJ |
| description | The effects of urban heat islands (UHIs) have a substantial bearing on the sustainability of cities and environs. This paper examines the efficacy of green and cool roofs as potential UHI mitigation strategies to make cities more resilient against UHI. We have employed the urbanized version of the Weather Research and Forecasting (uWRF) model at high (1 km) resolution with physically-based rooftop parameterization schemes (conventional, green and cool), a first-time application to the Chicago metropolitan area. We simulated a hot summer period (16–18 August 2013) and assessed (i) UHI reductions for different urban landuse with green/cool roofs, (ii) the interaction of lake breeze and UHI, and (iii) diurnal boundary layer dynamics. The performance of uWRF was evaluated using sensible heat flux and air temperature measurements from an urban mini-field campaign. The simulated roof surface energy balance captured the energy distribution with respective rooftop algorithms. Results showed that daytime roof temperature reduced and varied linearly with increasing green roof fractions, from less than 1 °C for the case of 25% green roof to ∼3 °C during peak daytime for 100% green roof. Diurnal transitions from land to lake breeze and vice versa had a substantial impact on the daytime cycle of roof surface UHI, which had a 3–4 hour lag in comparison to 2 m UHI. Green and cool roofs reduced horizontal and vertical wind speeds and affected lower atmosphere dynamics, including reduced vertical mixing, lower boundary layer depth, and weaker convective rolls. The lowered wind speeds and vertical mixing during daytime led to stagnation of air near the surface, potentially causing air quality issues. The selection of green and cool roofs for UHI mitigation should therefore carefully consider the competing feedbacks. The new results for regional land-lake circulations and boundary layer dynamics from this study may be extended to other urbanized areas, particularly to coastal areas. |
| first_indexed | 2024-03-12T16:06:40Z |
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| institution | Directory Open Access Journal |
| issn | 1748-9326 |
| language | English |
| last_indexed | 2024-03-12T16:06:40Z |
| publishDate | 2016-01-01 |
| publisher | IOP Publishing |
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| series | Environmental Research Letters |
| spelling | doaj.art-876b0c579ccd41698651b657962172982023-08-09T14:20:23ZengIOP PublishingEnvironmental Research Letters1748-93262016-01-0111606400410.1088/1748-9326/11/6/064004Green and cool roofs to mitigate urban heat island effects in the Chicago metropolitan area: evaluation with a regional climate modelA Sharma0P Conry1H J S Fernando2Alan F Hamlet3J J Hellmann4F Chen5Environmental Change Initiative, University of Notre Dame , 1400 East Angela Boulevard, Unit 117, South Bend, IN 46617, USA; Department of Civil & Environmental Engineering and Earth Sciences (CEEES), University of Notre Dame , 156 Fitzpatrick Hall, Notre Dame, IN 46556, USADepartment of Civil & Environmental Engineering and Earth Sciences (CEEES), University of Notre Dame , 156 Fitzpatrick Hall, Notre Dame, IN 46556, USADepartment of Civil & Environmental Engineering and Earth Sciences (CEEES), University of Notre Dame , 156 Fitzpatrick Hall, Notre Dame, IN 46556, USAEnvironmental Change Initiative, University of Notre Dame , 1400 East Angela Boulevard, Unit 117, South Bend, IN 46617, USA; Department of Civil & Environmental Engineering and Earth Sciences (CEEES), University of Notre Dame , 156 Fitzpatrick Hall, Notre Dame, IN 46556, USADepartment of Biological Sciences, University of Notre Dame , 100 Galvin Life Science Center, Notre Dame, IN 46556, USAResearch Application Laboratory, National Center for Atmospheric Research, 3450 Mitchell Lane, Boulder, CO 80301 USAThe effects of urban heat islands (UHIs) have a substantial bearing on the sustainability of cities and environs. This paper examines the efficacy of green and cool roofs as potential UHI mitigation strategies to make cities more resilient against UHI. We have employed the urbanized version of the Weather Research and Forecasting (uWRF) model at high (1 km) resolution with physically-based rooftop parameterization schemes (conventional, green and cool), a first-time application to the Chicago metropolitan area. We simulated a hot summer period (16–18 August 2013) and assessed (i) UHI reductions for different urban landuse with green/cool roofs, (ii) the interaction of lake breeze and UHI, and (iii) diurnal boundary layer dynamics. The performance of uWRF was evaluated using sensible heat flux and air temperature measurements from an urban mini-field campaign. The simulated roof surface energy balance captured the energy distribution with respective rooftop algorithms. Results showed that daytime roof temperature reduced and varied linearly with increasing green roof fractions, from less than 1 °C for the case of 25% green roof to ∼3 °C during peak daytime for 100% green roof. Diurnal transitions from land to lake breeze and vice versa had a substantial impact on the daytime cycle of roof surface UHI, which had a 3–4 hour lag in comparison to 2 m UHI. Green and cool roofs reduced horizontal and vertical wind speeds and affected lower atmosphere dynamics, including reduced vertical mixing, lower boundary layer depth, and weaker convective rolls. The lowered wind speeds and vertical mixing during daytime led to stagnation of air near the surface, potentially causing air quality issues. The selection of green and cool roofs for UHI mitigation should therefore carefully consider the competing feedbacks. The new results for regional land-lake circulations and boundary layer dynamics from this study may be extended to other urbanized areas, particularly to coastal areas.https://doi.org/10.1088/1748-9326/11/6/064004urban heat islandmitigationWRFgreen and cool roofsvertical mixingboundary layer |
| spellingShingle | A Sharma P Conry H J S Fernando Alan F Hamlet J J Hellmann F Chen Green and cool roofs to mitigate urban heat island effects in the Chicago metropolitan area: evaluation with a regional climate model Environmental Research Letters urban heat island mitigation WRF green and cool roofs vertical mixing boundary layer |
| title | Green and cool roofs to mitigate urban heat island effects in the Chicago metropolitan area: evaluation with a regional climate model |
| title_full | Green and cool roofs to mitigate urban heat island effects in the Chicago metropolitan area: evaluation with a regional climate model |
| title_fullStr | Green and cool roofs to mitigate urban heat island effects in the Chicago metropolitan area: evaluation with a regional climate model |
| title_full_unstemmed | Green and cool roofs to mitigate urban heat island effects in the Chicago metropolitan area: evaluation with a regional climate model |
| title_short | Green and cool roofs to mitigate urban heat island effects in the Chicago metropolitan area: evaluation with a regional climate model |
| title_sort | green and cool roofs to mitigate urban heat island effects in the chicago metropolitan area evaluation with a regional climate model |
| topic | urban heat island mitigation WRF green and cool roofs vertical mixing boundary layer |
| url | https://doi.org/10.1088/1748-9326/11/6/064004 |
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