https://doi.org/10.5194/acp-2020-600 Preprint. Discussion started: 27 July 2020 c Author(s) 2020. CC BY 4.0 License. 1 Sudden changes in nitrogen dioxide emissions over Greece 2 due to lockdown after the outbreak of COVID-19 3 Maria-Elissavet Koukouli1*, Ioanna Skoulidou1, Andreas Karavias2, Isaak Parcharidis2, Dimitris Balis1, Astrid 4 Manders3, Arjo Segers3, Henk Eskes4 and Jos van Geffen4 5 1 Laboratory of Atmospheric Physics, Aristotle University of Thessaloniki, Greece. 6 2 Department of Geography, Harokopio University, Athens, Greece. 7 3 TNO, Climate, Air and Sustainability, Utrecht, The Netherlands. 8 4 Royal Netherlands Meteorological Institute (KNMI), De Bilt, The Netherlands. 9 * Correspondence:
[email protected] 10 Abstract: The unprecedented order, in modern peaceful times, for near-total lockdown of the Greek population, 11 as means of protection against the Severe Acute Respiratory Syndrome CoronaVirus-2, commonly known as 12 COVID-19, infection, has brought unintentional positive side-effects to the country’s air quality levels. 13 S5P/TROPOMI monthly mean tropospheric nitrogen dioxide (NO2) observations show an average decrease of - 14 3% to -26% [-1% to -27%] with an average of -22% [-11%] for March and April 2020 respectively, compared to the 15 previous year, over the six larger Greek metropolitan areas, attributable mostly to vehicular emission reductions. 16 Furthermore, significant effects for shipping emissions over the Aegean Sea as well as the areas surrounding 17 major Greek ports were observed, of approximately -12% [-5%]. For the capital city of Athens, weekly analysis 18 was possible and it revealed a marked decline in NO2 load between -8% and -43% for seven of the eight weeks 19 studied.