Based on the dynamic downscaling by the regional climatemodel RegCM4 from three CMIP5 global models under the historical and theRCP4.5 simulations, this article evaluated the performance of the RegCM4downscaling simulations on the air environment carrying capacity (AEC) andweak ventilation days (WVDs) in China, which are applied to measure hazepollution potential. Their changes during the middle and the end of the 21stcentury were also projected. The evaluations show that the RegCM4downscaling simulations can generally capture the observed features of theAEC and WVD distributions over the period 1986–2005. The projectionsindicate that the annual AEC tends to decrease and the annual WVDs tend toincrease over almost the whole country except central China, concurrent withgreater change by the late 21st century than by the middle ofthe 21st century. It suggests that annual haze pollution potential would beenlarged under the RCP4.5 scenario compared to the present. For seasonalchange in the four main economic zones of China, it is projectedconsistently that there would be a higher probability of haze pollution riskover the Beijing–Tianjin–Hebei (BTH) region and the Yangtze River Delta(YRD) region in winter and over the Pearl River Delta (PRD) region in springand summer in the context of the warming scenario. Over Northeast China(NEC), future climate change might reduce the AEC or increase the WVDsthroughout the whole year, which favours the occurrence of haze pollution andthus the haze pollution risk would be aggravated. The relative contribution ofdifferent components related to the AEC change further indicates thatchanges in the boundary layer depth and the wind speed play leadingroles in the AEC change over the BTH and NEC regions. In addition to thosetwo factors, the precipitation change also exerts important impacts on theAEC change over the YRD and PRD zones.
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