Ground-based station observation of PM2.5, NO₂, SO₂, and ozone in eastern China

(A) Wuhan. (B) Beijing. (C) Guangzhou. (D) Shanghai. The figure compares the 3-week averages during the city lockdown period (CLD), the 3-week averages before 2020-CLD (pre-CLD), the 5-year climatology for 2015 to 2019 during the same period of 2020-CLD in the Chinese lunar calendar that covers the Lunar New Year (CLIM-LNY), and the 5-year climatology for 2015 to 2019 during the same period with 2020-CLD in the Gregorian calendar (CLIM).