Multidecadal ozone trends in China and implications for human health and crop yields: A hybrid approach combining chemical transport model and machine learning
Abstract. Surface ozone (O3) is well known to pose significant threats to both human health and crop production worldwide. However, a multi-decadal assessment of O3 impacts on public health and crop yields in China is lacking due to insufficient long-term continuous O3 observations. In this study, we used a machine learning (ML) algorithm to correct the biases of O3 concentrations simulated by the chemical transport model from 1981–2019 by integrating multi-source datasets. The ML-enabled bias correction offers improved performance in reproducing observed O3 concentrations, and thus further improves our estimates of O3 impacts on human health and crop yields. Our results show that a warm-season increasing trend of O3 in Beijing-Tianjin-Hebei and its surroundings (BTHs), Yangtze River Delta (YRD), Sichuan Basin (SCB) and Pearl River Delta (PRD) regions are 0.32 μg m–3 yr–1, 0.63 μg m–3 yr–1, 0.84 μg m–3 yr–1, and 0.81 μg m–3 yr–1 from 1981 to 2019, respectively. In more recent years, O3 concentrations experience more fluctuations in the four major regions. Our results show that only BTHs have a perceptible increasing trend of 0.81 μg m–3 yr–1 during 2013–2019. Meteorological factors play important roles in modulating the interannual variability of surface O3, wherein synoptic systems (e.g., high-pressure system, Western Pacific subtropical high, tropical cyclone) are closely related to the spatiotemporal distribution of regional O3 via influencing regional weather conditions and transport processes. The estimated annual all-cause premature deaths induced by O3 increased from ~55,900 in 1981 to ~162,000 in 2019 with an increasing trend of ~2,980 deaths yr–1. The annual premature deaths related to respiratory and cardiovascular disease are ~34,200 and ~40,300 in 1998, and ~26,500 and ~79,000 in 2019, having a rate of change of –546 and +1,770 deaths yr–1 during 1998–2019, respectively. The estimated annual crop relative yield loss (RYL) for wheat, rice, soybean, and maize is 3.3 %, 5.5 %, 10.6 %, and 2.6 % in 1981, and increases to 5.9 %, 6.8 %, 15.1 %, and 4.1 % in 2019, respectively. The average annual crop RYL from 1981 to 2019 for wheat, rice, soybean, and maize range between 1.1–7.2 %, 2.7–9.4 %, 6.3–24.8 %, and 0.8–7.4 %, respectively, using different concentration-based metrics. Our study, for the first time, used ML to provide a robust dataset of O3 concentrations over the past four decades in China, enabling a long-term evaluation of O3-induced crop losses and health impacts. These findings are expected to fill the gap in the long-term O3 trend and impact assessment in China.
Jia Mao et al.
Jia Mao et al.
Jia Mao et al.
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