Influence of ENSO on Tropospheric Ozone Variability in East Asia

Abstract

AbstractAbundance of tropospheric ozone is determined by the interplay among emissions, chemistry, and climate dependent transport. It is important to identify the essential factors that modulate ozone in China and Korea because of increasing ozone trends in this area. In this study, we investigated the correlations of tropospheric ozone in East Asia with El Niño Southern Oscillations (ENSO). The model simulated ozone from 2000 to 2020 with Community Atmosphere Model version 6 with chemistry (CAM6‐chem), ECMWF Atmospheric Composition Reanalysis data, and ozone profiles measured in South Korea, Japan, and Hong Kong. These data were utilized to understand the ozone–ENSO relationship in this region. We found that tropospheric ozone in East Asia is significantly correlated with the wintertime Niño 3.4 index in El Niño/La Niña developing summer and decaying spring, with correlation coefficient up to 0.9. Particularly tropospheric ozone originated from stratosphere is strongly correlated with the Niño 3.4 index. Ozone concentrations in China and the Korean Peninsula are ∼5 ppb higher during El Niño developing summer compared to La Niña in a broad area, because of anomalous cyclonic/anticyclonic flows in the extratropics. In El Niño/La Niña decaying spring, the opposite occurs in the same region. In the decaying spring, stronger variability was observed in the subtropical regions of the lower to mid troposphere, indicating higher ozone concentrations during El Niño compared to La Niña. This variability is associated with the fluctuations in the Walker circulation, large‐scale sinking/rising motions, and the accompanying biomass burning events. The model reproduced the ozone variability associated with ENSO in the ozonesonde observations.