“…Substantial efforts among the research community have been devoted to characterizing the NO x emission responses in the early phase of the pandemic (Gkatzelis et al, 2021, and references therein). Satellite-observed NO 2 tropospheric column amounts have been used to infer COVID-induced NO x emission perturbations through chemical transport models (CTMs) (Miyazaki et al, 2020;Ding et al, 2020;Riess et al, 2022;Kang et al, 2022), fitting of plume dispersion or box models (Sun et al, 2021;Lange et al, 2022;Dammers et al, 2022;Xue et al, 2022;Godłowska et al, 2023;Zhang et al, 2023), and calculation of the divergence of horizontal NO 2 flux (the flux divergence approach hereafter, de Foy and Schauer, 2022; Dix et al, 2022;Rey-Pommier et al, 2022;Chen et al, 2023). Each approach comes with its own strengths and limitations.…”