Analysis of the meteorological factors affecting the short-term increase in O3 concentrations in nine global cities during COVID-19
Zhongsong Bi, Zhixiang Ye, Chao He, Yunzhang Li
Abstract
Surface ozone (O 3 ) is a major air pollutant around the world. This study investigated O 3 concentrations in nine cities during the Coronavirus disease 2019 (COVID-19) lockdown phases. A statistical model, named Generalized Additive Model (GAM), was also developed to assess different meteorological factors , estimate daily O 3 release during COVID-19 lockdown and determine the relationship between the two. We found that: (1) Daily O 3 significantly increased in all selected cities during the COVID-19 lockdown, presenting relative increases from −5.7% (in São Paulo) to 58.9% (in Guangzhou), with respect to the average value for the same period in the previous five years. (2) In the GAM model, the adjusted coefficient of determination (R 2 ) ranged from 0.48 (Sao Paulo) to 0.84 (Rome), and it captured 51–85% of daily O 3 variations. (3) Analyzing the expected O 3 concentrations during the lockdown, using GAM fed by meteorological data , showed that O 3 anomalies were dominantly controlled by meteorology. (4) The relevance of different meteorological variables depended on the cities. The positive O 3 anomalies in Beijing, Wuhan, Guangzhou, and Delhi were mostly associated with low relative humidity and elevated maximum temperature. Low wind speed , elevated maximum temperature, and low relative humidity were the leading meteorological factors for O 3 anomalies in London , Paris, and Rome . The two other cities had different leading factor combinations.