Adaptation strategies for urban warming: Assessing the impacts of heat waves on cooling capabilities in Chongqing, China

Abstract

Cool and green roofs are two important adaptation strategies to mitigate urbanization-driven warming. Assessment of the impact of some extreme weather events on their cooling capability can help us understand the potential of urban adaptation to future climate change and then make scientific management decisions. We used the weather research and forecasting (WRF) model to simulate the changes in 2-m air temperature caused by urban land expansion in 2010–2030 and cool/green roofs over the main urban areas of Chongqing and then focused on a comparative analysis of temperature variations between heat wave and nonheat wave periods. The summer daily averaged warming induced by urban land expansion from 2010 to 2030 in the heat wave and nonheat wave periods was 0.82 °C and 0.62 °C, respectively. Under the influences of cool and green roofs, the cooling extent over most urban areas was larger during heat wave days than during nonheat wave days and even spread to the surrounding nonurban areas. Therefore, heat waves did not trigger a significant increment of daily cooling intensity over the urban areas. The local offsetting rates (the ability of cooling by an adaptive strategy to offset urban warming) of CRs and GRs in heat waves was lower than that in nonheat waves. So heat waves will weaken the urban adaptations to future urbanization-driven warming.