Alessandro Damiani, Hitoshi Irie, Dmitry A. Belikov, Shuei Kaizuka, Hossain Mohammed Syedul Hoque, Raul R. Cordero
Atmospheric Chemistry and Physics 22(18) 12705-12726 2022年9月29日 査読有り
Abstract. This study investigated the spatiotemporal variabilitiesin nitrogen dioxide (NO2), formaldehyde (HCHO), ozone (O3), andlight-absorbing aerosols within the Greater Tokyo Area, Japan, which is the mostpopulous metropolitan area in the world. The analysis is based on totaltropospheric column, partial tropospheric column (within the boundarylayer), and in situ observations retrieved from multiple platforms as well as additionalinformation obtained from reanalysis and box model simulations. This studymainly covers the 2013–2020 period, focusing on 2020 when air quality wasinfluenced by the coronavirus 2019 (COVID-19) pandemic. Although total andpartial tropospheric NO2 columns were reduced by an average of about10 % in 2020, reductions exceeding 40 % occurred in some areas duringthe pandemic state of emergency. Light-absorbing aerosol levels within theboundary layer were also reduced for most of 2020, while smallerfluctuations in HCHO and O3 were observed. The significantly enhanceddegree of weekly cycling of NO2, HCHO, and light-absorbing aerosolfound in urban areas during 2020 suggests that, in contrast to othercountries, mobility in Japan also dropped on weekends. We conclude that,despite the lack of strict mobility restrictions in Japan, widespreadadherence to recommendations designed to limit the COVID-19 spread resultedin unique air quality improvements.