Tropospheric ozone production and chemical regime analysis during the COVID-19 lockdown over Europe

Abstract. The COVID-19 (coronavirus disease 2019) European lockdowns have led to a significant reduction in the emissions of primary pollutants such as NO (nitric oxide) and NO2 (nitrogen dioxide). As most photochemical processes are related nitrogen oxide (NOx≡ + NO2) chemistry, this event has presented an exceptional opportunity investigate its effects on air quality secondary pollutants, tropospheric ozone (O3). In study, we present lockdown atmospheric trace gas concentrations, net production rates (NOPRs) dominant chemical regime throughout troposphere based three different research aircraft campaigns across Europe. These UTOPIHAN (Upper Tropospheric Ozone: Processes Involving HOx NOx) 2003 2004, HOOVER (HOx over Europe) 2006 2007, BLUESKY campaign 2020, latter performed during lockdown. We situ observations simulation results from ECHAM5 (fifth-generation Centre Hamburg general circulation model, version 5.3.02)/MESSy2 (second-generation Modular Earth Submodel System, 2.54.0) Atmospheric Chemistry (EMAC), model which allows for scenario calculations with business-as-usual campaign, referred “no-lockdown scenario”. show that reduced mixing ratios upper by around 55 % compared no-lockdown due traffic. O3 loss terms reflected deceleration cycling NOx, while NOPRs were largely unaffected. also study role methyl peroxyradicals forming HCHO (αCH3O2) shifted chemistry upper-troposphere–tropopause region NOx-limited BLUESKY. comparison, find volatile organic compound (VOC)-limited be UTOPIHAN.