Relationship between synoptic meteorology and daily surface O3 variation over China

Abstract

The diurnal variation of ozone (O₃) in China is severely affected by weather processes. In this study, the influence mechanism was further extracted through the coherent wave analysis (CWA) and multivariate empirical orthogonal function (MEOF) methods. The multi-factor time series correlation indicates that there is a significant correlation between the daily O₃ and meteorological factors variability within 1–3 weeks. Considering the high-altitude circulation, O₃ pollution often occurs behind the trough and in front of the ridge. Under this circulation pattern, hot and dry, less cloudy weather often occurs, which leads to an increase in the level of solar radiation reaching the ground. Higher temperatures and solar radiation promote photochemical reactions, and dry weather is not conducive to the removal of O₃ either. These conditions are all conducive to the generation and accumulation of O₃ in terms of dynamics, thermodynamics and photochemistry, etc. This further explains that the fluctuations of the mid-latitude westerlies have guided this change process. Atmospheric circulation drives the near-surface weather patterns, which further affect the near-surface O₃ patterns. This composite pattern further dominated the diurnal variations in the four key polluted areas. The dominant effect of the T/RH pattern on the diurnal variation of O₃ is greater than that of the dynamic field. The leading four PCs of the T/RH/O₃ field explain 57.4 %, 43.6 %, 32.9 % and 39.6 % of the NCP, YRD, PRD, and SCB O₃ variability, respectively. However, the leading four PCs of the SP/W/O₃ field explain 30.3 %, 36.7 %, 12.4 %, and 23.7 % of them, respectively.