[A-AS07] 大気化学

[AAS07-23] Changes in Air Quality in the Greater Tokyo Area during the COVID-19 pandemic

*Alessandro Damiani¹、Hitoshi Irie¹、Dmitry Belikov¹、Hossain Mohammed Syedul Hoque²、Raul Cordero³ (1.CEReS, Chiba University、2.Nagoya University、3.Santiago University)

キーワード：air quality, covid-19, trace gases

This study investigated the spatiotemporal variabilities in trace gases and aerosols within the Greater Tokyo Area (GTA). The analysis was based mainly on the total column, partial column, and updated in-situ observations retrieved from multiple platforms as well as additional information obtained from reanalysis and simulations. The analysis covers the 2013–2020 period, focusing on 2020 when the reduced mobility caused by COVID-19 affected air quality. Overall, diurnal nitrogen dioxide (NO₂) columns in 2020 decreased by about 10% annually, with more significant reductions in limited areas during the pandemic state of emergency. On the other hand, based on in-situ daily observations, a machine-learning approach to account for the meteorology showed a more homogeneous reduction over the GTA.
Light-absorbing aerosol levels were also reduced for most of 2020, while minor fluctuations in formaldehyde (HCHO) and ozone (O₃) were observed. The significantly enhanced degree of weekly cycling of NO₂, HCHO, and light-absorbing aerosol found in urban areas during 2020 suggests that Japan's mobility consistently dropped also on weekends in contrast to other countries. Therefore, despite Japan's lack of strict mobility restrictions, widespread adherence to recommendations designed to limit the COVID-19 spread resulted in unique air quality improvements.