Meteorology driving the highest ozone level occurred during mid-spring to early summer in Shanghai, China

More recent studies highlighted the aggravated surface ozone (O-3) pollutions occurred in Spring and Autumn in China, but presenting clear distinctions for different cities. In this study, we observed the most elevated mean daily and maximum daily 8-h (MDA8) O-3 concentrations occurred from mid-Spring to early Summer (April, May and June, AMJ) at both urban and remote sites in Shanghai compared to other warm months (March, July, August, September, October), based on the long-term measurements from 2010 to 2019. The typical weather pattern of G-SW (High pressure with predominant winds of southwesterly) recognized by T-mode principal component approach (T-PCA), exhibits the strongest solar radiation and highest daily maximum temperature relative to other weathers in AMJ, leading to not only the most elevated O-3 concentration, but also the largest O-3 increasing variability in daytime. More importantly, under the G-SW weather condition, the MDA8 O-3 concentration presents the greatest increasing rate at 3.95 ppbv/yr from 2010 to 2019 in Shanghai downtown compared to other weather patterns, suggesting that more occurrence and faster exacerbation of O-3 pollutions could be expected under the G-SW weather condition in the future. To understand and mitigate high O-3 occurrences under the weather pattern of G-SW during AMJ, process analysis by a chemical/dynamical model (WRF-Chem, Weather Research and Forecasting (WRF) model coupled with Chemistry) is conducted to elucidate the strong O-3 productivity (19 ppbv/h in daytime), that dominates the high O-3 occurrence under the G-SW weather condition. Sensitive studies suggest that under the G-SW weather condition, reduction of VOCs emissions is very effective to prevent the high O-3 pollution in Shanghai. The model results show that photochemical productivity decreases by 35% in daytime response to 30% reduction of VOCs emissions, leading to 17.6% mitigation of peak O-3 concentration in Shanghai downtown. This result provides valuable information for the development of emission control strategy in Shanghai under different weather conditions. (C) 2021 Published by Elsevier B.V