Distinct Regimes of O3 Response to COVID-19 Lockdown in China

Restrictions on human activities remarkably reduced emissions of air pollutants in China during the COVID-19 lockdown periods. However, distinct responses O3 concentrations were observed across China. In Beijing–Tianjin–Hebei (BTH) and Yangtze River Delta (YRD) regions, enhanced by 90.21 71.79% from pre-lockdown to periods 2020, significantly greater than equivalent for same over 2015–2019 (69.99 43.62%, p < 0.001). contrast, a decline was detected (?1.1%) Pearl (PRD) region. To better understand underlying causes these inconsistent China, we adopted least absolute shrinkage selection operator (Lasso) ordinary linear squares (OLS) methods this study. Statistical analysis indicated that sharp nitrogen dioxide (NO2) major driver BTH region as it is NOx-saturated YRD region, season-shift induced changes temperature/shortwave radiative flux, while declines NO2, attributable rise O3. PRD slight drop attributed decreased intensity radiation. The regimes response offer important insights into different control strategies