Responses of the Atmospheric Age of PM 2.5 to Changes in Meteorology and Emissions in China From 2013 to 2020
Xiaodong Xie, Yang Xiang, Jianlin HuAbstract
The clean air actions in China since 2013 have decreased fine particulate matter (PM 2.5 ) concentrations significantly, however, their impacts on the atmospheric age of PM 2.5 remain unclear. Here, we updated the age‐resolved Community Multiscale Air Quality (CMAQ) model to quantify the impacts of changes in anthropogenic emissions and meteorological conditions on the atmospheric age of PM 2.5 in China from 2013 to 2020. The results indicated that PM 2.5 concentrations decreased by 39.6% in central‐eastern China, primarily driven by anthropogenic emission reductions. The mean atmospheric age of PM 2.5 in most of China increased in April and July and decreased in October. In January, the mean age of PM 2.5 increased by ∼8.5 hr in the Beijing‐Tianjin‐Hebei region, while it decreased by 5.8–6.7 hr in the Pearl River Delta. Meteorological conditions are the dominant factors influencing PM 2.5 age, accounting for 56% in Beijing–Tianjin–Hebei, 39% in the Yangtze River Delta, 56% in the Pearl River Delta, 74% in the Sichuan Basin, and 60% in the Fenwei Plain. Emission reductions increased the atmospheric age of PM 2.5 in most of China from 2013 to 2020, with a maximum increase of ∼16 hr during July and April. Our results demonstrate that the best time to start emission control under stable weather conditions needs to be 5–15 hr earlier than that on normal days. With the air quality continuously improving, future short‐term emission controls, especially for large public events, shall be started earlier than before.