Quantification of the Impact of the Lockdown on NOx and NMVOC Emissions over Europe and Implications for Surface Ozone and HOx Chemistry: A Non-Linear Multi-Species Inverse Modeling using TROPOMI

Abstract:

The slow down in anthropogenic activities due to the COVID-19 pandemic had an immediate and sweeping impact on air pollution. Several scientific studies have shown the extent of changes in relevant air pollutants using diverse monitoring systems. Because of the ambient concentrations of pollutants are driven by a large number of factors such as energy patterns (expected changes), meteorology, and chemical feedbacks, teasing out the impact of the pandemic on air pollution requires advance observation systems that combine state-of-the-art observations, chemical modeling and inversion techniques. To properly account for these additional effects, we provide the optimal estimate of NO_x and VOC emissions using a jointly non-linear analytical inversion method proposed in Souri et al. (2020) using well-characterized TROPOMI HCHO and NO₂ observations during 2019 (baseline year) and 2020 (pandemic year) over Europe. Performing the inversion not only enable us to precisely quantify the impact of the pandemic on emissions (along with their uncertainty) but also paves the way for estimating the resulting changes on secondary chemical pathways of several species such as ozone and sulfate.