Green Roof Mitigation Potential for a Proxy Future Climate Scenario in Chicago, Illinois

Abstract

The Advanced Research version of the Weather Research and Forecasting Model (ARW) coupled with an urban canopy model is used to investigate the potential of vegetative (green) roof technology to mitigate against ongoing climate warming and continued urban sprawl for a day representing average summer conditions in late-twenty-first-century Chicago, Illinois. Effects related particularly to human health hazards resulting from excessive heat and high pollution concentrations are emphasized. Continued expansion of the urban environment over the next century is shown to lead to an expansion of the warming signal across the metropolitan region. Widespread adoption of vegetative rooftops, through increased albedo and evapotranspiration, reduces temperatures in the urban environment by as much as 38C, an effect similar to the simpler but less appealing alternative of employing painted or other reflective rooftop structures (e.g., white roofs). A significant limitation to the green roof approach for the case studied is that the increase in moisture resulting from transpiration leads to only marginal cooling when apparent temperatures are considered. An additional complication arises in that the reduced temperatures alter the lake-breeze circulation, potentially reducing circulation of pollutants into the city core, but also reducing natural cooling in the most urbanized areas during the climatologically warmest hours. Future work that evaluates these impacts over a broader range of synoptic settings, documents changes in the planetary boundary layer structure and attendant pollution, and considers the multiple-day dependence of these effects is needed.

Observation and Estimation of Evapotranspiration from an Irrigated Green Roof in a Rain-Scarce Environment

“…As a stormwater management strategy applied since the 1960s [6], they have been found to reduce runoff flow rate, volume, and response time-all important for reducing stormwater impacts [6][7][8][9][10][11][12]. Green roofs also bring other environmental benefits to the urban ecosystem, including heat island relief, air quality improvement, habitat and biodiversity provision, and food production [3,6,7,[13][14][15][16][17][18][19][20][21].…”

Seasonal and Diurnal Thermal Performance of a Subtropical Extensive Green Roof: The Impacts of Background Weather Parameters

“…The literature has generated extensive studies on green-roof thermal effects in various climatic contexts. These studies roughly fall into three categories in terms of study approaches and objectives, including: (1) on-site monitoring to investigate green-roof impacts on summer temperature parameters and building heat flux patterns [9][10][11][12][13][14][15][16][17][18][19][20][21][22]; (2) dynamic energy modeling to analyze the heat and moisture processes within the green-roof layers and identify key influential factors [23][24][25][26][27][28]; and (3) building energy simulation or meso-scale climatic modeling to predict the cooling and energy effects of individual or multiple green-roof installations [29][30][31][32][33][34]. The studies have reported that green roofs can reduce summer daily peak surface temperature by 15 °C-45 °C and peak air temperature by up to 5 °C.…”

Outdoor thermal comfort by different heat mitigation strategies- A review

“…Depending on the adoption scale, the cooling effect varies. Smith and Roebber [56] studied the adoption of green roofs during a typical summer day in Chicago, Illinois. They used the Weather Research and Forecasting Model (ARW) [57] coupled with an urban canopy model.…”