The effectiveness of cool and green roofs as urban heat island mitigation strategies

By Dan Li, E. Bou‐Zeid, M. Oppenheimer. 2014

500 citations recorded by the source corpus.

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 (). 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.

Subfields: Atmospheric Science, Environmental Engineering, Global and Planetary Change

View Paper: https://www.semanticscholar.org/paper/bd6317a670df011521322a003363c8a1c3d9af0e

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Atmospheric Science

In Environmental Engineering

In Global and Planetary Change

Citations in the corpus

Climate–vegetation control on the diurnal and seasonal variations of surface urban heat islands in China (2016, background): “Therefore, understanding and mitigating UHIs have gained strong interest from scientists and urban planners and have been the subject of active research (Kolokotroni et al 2012, Li and Bou-Zeid 2013, 2014, Li et al 2014, 2015, Zhao et al 2014).”
Micrometeorological simulations to predict the impacts of heat mitigation strategies on pedestrian thermal comfort in a Los Angeles neighborhood (2016, background): “Most past studies on the impacts of heat mitigation strategies have generally investigated the mesoscale meteorological consequences of hypothetical city-wide deployments of these strategies using numerical weather prediction models [14-28].”
Urban versus conventional agriculture, taxonomy of resource profiles: a review (2016, background): “A negative consequence of UA is that runoff from urban farms may contain high nutrient loads that could exceed local assimilative capacity if these systems are scaled up within cities (Emilsson et al. 2007; Li and Babcock 2014).”
Contrasting responses of urban and rural surface energy budgets to heat waves explain synergies between urban heat islands and heat waves (2015, background): “…regional and global climate models has been the subject of research recently (Oleson et al 2010, Jacobson and Ten Hoeve 2012, Georgescu et al 2014, Li et al 2014, Stone et al 2014), which is partly attributed to advances in urbanmodeling (Taha 2008a, 2008b, 2008c, Grimmond et al 2010, Chen et al…”
Interactions between urban heat islands and heat waves (2018, background): “Urban adaptation and mitigation strategies that involve increasing the green fraction/water availability such as green roof and street vegetation (Georgescu et al 2014, Li et al 2014, Zhao et al 2017) could help reduce the synergistic effects.”
Quality and sensitivity of high-resolution numerical simulation of urban heat islands (2014, methodology): “…paper that examines the effectiveness of different mitigation strategies, the simulations span from 0000UTC 6 June to 1200UTC 10 June 2008 (Li et al 2014) since there we introduce cool and green roofs that alter the urban microclimate and a warm-up period is thus needed to reduce the…”