The effectiveness of cool and green roofs as urban heat island mitigation strategies
Mitigation of the urban heat island (UHI) effect at the city-scale is investigated using the Weather Research and Forecasting (WRF) model in conjunction with the Princeton Urban Canopy Model (PUCM). Specifically, the cooling impacts of green roof and cool (white/high-albedo) roof strategies over the...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
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IOP Publishing
2014-01-01
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| Series: | Environmental Research Letters |
| Subjects: | |
| Online Access: | https://doi.org/10.1088/1748-9326/9/5/055002 |
| _version_ | 1797747941448876032 |
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| author | Dan Li Elie Bou-Zeid Michael Oppenheimer |
| author_facet | Dan Li Elie Bou-Zeid Michael Oppenheimer |
| author_sort | Dan Li |
| collection | DOAJ |
| description | Mitigation of the urban heat island (UHI) effect at the city-scale is investigated using the Weather Research and Forecasting (WRF) model in conjunction with the Princeton Urban Canopy Model (PUCM). Specifically, the cooling impacts of green roof and cool (white/high-albedo) roof strategies over the Baltimore-Washington metropolitan area during a heat wave period (7 June–10 June 2008) are assessed using the optimal set-up of WRF-PUCM described in the companion paper by Li and Bou-Zeid ( 2014 ). Results indicate that the surface UHI effect (defined based on the urban–rural surface temperature difference) is reduced significantly more than the near-surface UHI effect (defined based on urban–rural 2 m air temperature difference) when these mitigation strategies are adopted. In addition, as the green and cool roof fractions increase, the surface and near-surface UHIs are reduced almost linearly. Green roofs with relatively abundant soil moisture have comparable effect in reducing the surface and near-surface UHIs to cool roofs with an albedo value of 0.7. Significant indirect effects are also observed for both green and cool roof strategies; mainly, the low-level advection of atmospheric moisture from rural areas into urban terrain is enhanced when the fraction of these roofs increases, thus increasing the humidity in urban areas. The additional benefits or penalties associated with modifications of the main physical determinants of green or cool roof performance are also investigated. For green roofs, when the soil moisture is increased by irrigation, additional cooling effect is obtained, especially when the ‘unmanaged’ soil moisture is low. The effects of changing the albedo of cool roofs are also substantial. These results also underline the capabilities of the WRF-PUCM framework to support detailed analysis and diagnosis of the UHI phenomenon, and of its different mitigation strategies. |
| first_indexed | 2024-03-12T15:58:49Z |
| format | Article |
| id | doaj.art-976e5a3cb8ae4f8684353c49245f559a |
| institution | Directory Open Access Journal |
| issn | 1748-9326 |
| language | English |
| last_indexed | 2024-03-12T15:58:49Z |
| publishDate | 2014-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | Environmental Research Letters |
| spelling | doaj.art-976e5a3cb8ae4f8684353c49245f559a2023-08-09T14:45:54ZengIOP PublishingEnvironmental Research Letters1748-93262014-01-019505500210.1088/1748-9326/9/5/055002The effectiveness of cool and green roofs as urban heat island mitigation strategiesDan Li0Elie Bou-Zeid1Michael Oppenheimer2Department of Civil and Environmental Engineering, Princeton University , Princeton, NJ 08540, USADepartment of Civil and Environmental Engineering, Princeton University , Princeton, NJ 08540, USAWoodrow Wilson School of Public and International Affairs, Princeton University , Princeton, NJ 08540, USA; Department of Geosciences, Princeton University , Princeton, NJ 08540, USAMitigation of the urban heat island (UHI) effect at the city-scale is investigated using the Weather Research and Forecasting (WRF) model in conjunction with the Princeton Urban Canopy Model (PUCM). Specifically, the cooling impacts of green roof and cool (white/high-albedo) roof strategies over the Baltimore-Washington metropolitan area during a heat wave period (7 June–10 June 2008) are assessed using the optimal set-up of WRF-PUCM described in the companion paper by Li and Bou-Zeid ( 2014 ). Results indicate that the surface UHI effect (defined based on the urban–rural surface temperature difference) is reduced significantly more than the near-surface UHI effect (defined based on urban–rural 2 m air temperature difference) when these mitigation strategies are adopted. In addition, as the green and cool roof fractions increase, the surface and near-surface UHIs are reduced almost linearly. Green roofs with relatively abundant soil moisture have comparable effect in reducing the surface and near-surface UHIs to cool roofs with an albedo value of 0.7. Significant indirect effects are also observed for both green and cool roof strategies; mainly, the low-level advection of atmospheric moisture from rural areas into urban terrain is enhanced when the fraction of these roofs increases, thus increasing the humidity in urban areas. The additional benefits or penalties associated with modifications of the main physical determinants of green or cool roof performance are also investigated. For green roofs, when the soil moisture is increased by irrigation, additional cooling effect is obtained, especially when the ‘unmanaged’ soil moisture is low. The effects of changing the albedo of cool roofs are also substantial. These results also underline the capabilities of the WRF-PUCM framework to support detailed analysis and diagnosis of the UHI phenomenon, and of its different mitigation strategies.https://doi.org/10.1088/1748-9326/9/5/055002green roofcool roofurban canopy modelurban heat island mitigationWRF |
| spellingShingle | Dan Li Elie Bou-Zeid Michael Oppenheimer The effectiveness of cool and green roofs as urban heat island mitigation strategies Environmental Research Letters green roof cool roof urban canopy model urban heat island mitigation WRF |
| title | The effectiveness of cool and green roofs as urban heat island mitigation strategies |
| title_full | The effectiveness of cool and green roofs as urban heat island mitigation strategies |
| title_fullStr | The effectiveness of cool and green roofs as urban heat island mitigation strategies |
| title_full_unstemmed | The effectiveness of cool and green roofs as urban heat island mitigation strategies |
| title_short | The effectiveness of cool and green roofs as urban heat island mitigation strategies |
| title_sort | effectiveness of cool and green roofs as urban heat island mitigation strategies |
| topic | green roof cool roof urban canopy model urban heat island mitigation WRF |
| url | https://doi.org/10.1088/1748-9326/9/5/055002 |
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