Abstract
Anthropogenic activities, by far the largest source of NOx into the atmosphere, induce a weekly cycle of NO2 abundances in cities. Comprehensive analysis of the 2005–2017 OMI NO2 dataset reveals significant weekly cycles in 115 of the 274 cities considered. These results are corroborated by a full year of high-resolution TROPOMI NO2 observations. The OMI dataset permits us to identify trends in the weekly cycle resulting from NOx emissions changes. The data show a clear weakening of the weekly cycle over European and U.S. cities, an evolution attributed to the decline in anthropogenic emissions and the resulting growing importance of background NO2, whereas NO2 lifetime changes also play a minor role. In particular, the Sunday NO2 columns averaged over all U.S. cities are found to increase, relative to the weekly average, from 0.72 during 2005–2007 to 0.88 in 2015–2017. The opposite tendency is recorded in regions undergoing rapid emission growth. Multiyear simulations over the U.S. and the Middle East using the chemistry-transport model MAGRITTEv1.1 succeed in capturing the observed weekly cycles over the largest cities, as well as the observed long-term trends in the weekly cycle.
Highlights
Anthropogenic activities, by far the largest source of NOx into the atmosphere, induce a weekly cycle of NO2 abundances in cities
Tropospheric Monitoring Instrument (TROPOMI) results are very consistent with OMI results from year 2017, with Friday ratios of 0.84, 0.84 and 0.81, respectively. These results suggest a strengthening of the weekly cycle since 2005, www.nature.com/scientificreports likely due to the increase in NOx levels and the resulting declining background contribution and NO2 lifetime shortening over Iraqi cities, following the lines discussed above (Eq 1)
NOx emission trends cause significant changes in the weekly cycle, which are detected in the satellite data
Summary
Anthropogenic activities, by far the largest source of NOx into the atmosphere, induce a weekly cycle of NO2 abundances in cities. The NOx weekly cycle was previously investigated using ground-based, aircraft and satellite measurements[6,7,8], whereas spatial patterns observed from satellites were used to study the urban photochemistry with the help of models[9] These studies, rely either on relatively short data records of at most several months[8,9] or on satellite data from coarse resolution sounders[6,7]. We use NO2 column data from two nadir-viewing satellite sensors, the Ozone Monitoring Instrument (OMI10) launched in July 2004, and the high-resolution Tropospheric Monitoring Instrument (TROPOMI), single payload of the Sentinel-5 Precursor (S5P) launched in October 201711 Both sensors have an equatorial crossing time of ca. The observed cycles are further evaluated using multiyear simulations of the MAGRITTE model[12] over major cities in the U.S and the Middle East
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
