The evolving nature of the COVID-19 pandemic necessitates timely estimates of the resultant perturbations to anthropogenic emissions. Here we present a novel framework based on the relationships between observed column abundance and wind speed to rapidly estimate the air-basin-scale NO_x emission rate and apply it at the Po Valley in Italy using OMI and TROPOMI NO₂ tropospheric column observations. The NO_x chemical lifetime is retrieved together with the emission rate and found to be 15–20 h in winter and 5–6 h in summer. A statistical model is trained using the estimated emission rates before the pandemic to predict the trajectory without COVID-19. Compared with this business-as-usual trajectory, the real emission rates show three distinctive drops in March 2020 (−42 %), November 2020 (−38 %), and March 2021 (−39 %) that correspond to tightened COVID-19 control measures. The temporal variation of pandemic-induced NO_x emission changes qualitatively agrees with Google and Apple mobility indicators. The overall net NO_x emission reduction in 2020 due to the COVID-19 pandemic is estimated to be 22 %.

中文翻译：

---

一种卫星数据驱动的框架，可在 COVID-19 大流行期间快速量化空气流域规模的 NOx 排放及其在波谷的应用

COVID-19 大流行的不断演变的性质需要及时估计对人为排放造成的扰动。在这里，我们提出了一种基于快速观测柱丰度和风速的关系的新颖框架估计空气流域尺度NO _X排放率并使用OMI和TROPOMI NO在意大利在宝谷应用它_2个对流层柱观测。该NO _X化学寿命与排放率一起检索，发现冬季为 15-20 小时，夏季为 5-6 小时。使用大流行之前估计的排放率训练统计模型，以预测没有 COVID-19 的轨迹。与这种一切照旧的轨迹相比，实际排放率在 2020 年 3 月 ( -42  % )、2020 年 11 月 ( -38  % ) 和 2021 年 3 月 ( -39  % )出现了三个明显的下降，这与 COVID-19 收紧相对应控制措施。流行诱导NO的时间变化_X排放的变化与谷歌和苹果的流动性指标，定性一致。整体净NO _x由于 COVID-19 大流行，2020 年的排放量估计为22  %。