Interaction of urban heat islands and heat waves under current and future climate conditions and their mitigation using green and cool roofs in New York City and Phoenix, Arizona

Abstract

Urban environments and heat waves interact synergistically and aggravate the thermal environment through the urban heat island (UHI) effect. Of concern is the potential for a projected warmer future climate to further compound heat waves in urban environments. The present study investigates the interaction of a 2006 heat wave in North America with two urban environments (Phoenix and New York City (NYC)) in current climate and future climate simulations. The future climate conditions were generated using the pseudo-global warming methodology. Multiple high-resolution (3 km) simulations were performed using the weather research and forecasting (WRF) model coupled with the single-layer urban canopy model to improve representation of urban processes and we explore how irrigated green roofs and cool roofs can mitigate heat wave amplification by UHIs. To quantify heat wave intensity, an analytical model is applied to the WRF model output that considers the urban surface heat and water vapor exchanges with the atmosphere. A future, warmer climate is found to amplify the UHI intensity during heat waves in both Phoenix (21%) and NYC (48%), but the amplification is of great uncertainty as its magnitude is comparable to the temporal variability of temperatures. The increase in urban heat index can be almost completely offset by adopting irrigated green roofs in urban areas, and partially offset by adopting cool roofs.

Predicting impacts of weather-driven urban disasters in the current and future climate

“…The effect of climate change will be experienced to a greater extent in cities compared with the surrounding rural areas given expected increases in temperature and the vulnerability of the environment to more extreme weather events. In a recent article, Tewari et al studied the interaction of urban heat island and heat waves under current and future climate conditions and found that urban heat island intensity during heat-wave periods and in a warmer climate gets amplified in two large and growing U.S. metropolitan areas [42]. Specifically, they found that the intensity is increased by 21% in Phoenix, AZ, USA, and 48% in New York City for the 2070-2090 period.…”

Asian megacity heat stress under future climate scenarios: impact of air-conditioning feedback

“…Although future urban air temperatures have been explored both globally and locally (e.g. Adachi et al 2012, Kusaka et al 2012, Kusaka et al 2016, Hamdi et al 2014, Grossman-Clarke et al 2016, Conlon et al 2016, Krayenhoff et al 2018, Tewari et al 2019, Darmanto et al 2019, Takane et al 2019, Lipson et al 2019, few studies have examined the impact on human heat stress in cities. As global climate model (GCM) simulations (e.g.…”

Enhanced sensitivity of the urban heat island effect to summer temperatures induced by urban expansion

“…The difference between urban and rural areas in evaporation and anthropogenic heat release contributes to the enhanced UHI effect during heatwaves compared to normal days. Such a phenomenon is found in a wide range of cities (Li et al 2015, Schatz and Kucharik 2015, Ramamurthy and Bou-Zeid 2017, Tewari et al 2019. Considering that the heat risks in urban areas are closely relevant to background temperature and the UHI intensity (Gabriel and Endlicher 2011), it is necessary to investigate the relationship between temperature and the UHI effect (T-UHI).…”