Ozone and NOx data
Information on atmospheric nitrogen (NOx) and ozone (O3) were obtained from the Tropospheric Monitoring Instrument (TROPOMI), hosted by the European Space Agency’s (ESA) Sentinel‐5P satellite under the Copernicus programme (https://sentinel.esa.int/web/sentinel/missions/sentinel-5p). The Sentinel-5 Precursor mission is the first Copernicus mission dedicated to monitoring our atmosphere and provides information and services on air quality, climate, ozone (O3) and Nitrogen dioxide (NO2) between the surface and the top of the troposphere and the ozone layer. The spatial resolution of the Sentinel-5P is 7×3.5 km. Data of O3 and NO2 were extracted using the NASA Panoply 4.11.1 software (NASA 2020) (Fig. 2).
To generate mean NO2 and O3 values over our specific sites, we extract daily values from TROPOMI layers between may 2019 (first of the TROPOMI-Sentinal5P products was released at the end of April 2019) and September 2019. We did not include data from 2020 in our mean calculation, due to the unusual change in human activity caused by covid-19 health crises. While nitrogen oxides are one of the several precursor of ozone (Mills et al. 2013), O3 and NO2 are not correlated (cor = 0.070; p-value = 0.421).