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\begin{document}

\title{Did the COVID-19 Crisis Reduce Free Tropospheric Ozone across the
Northern Hemisphere?}



\author[1]{Wolfgang Steinbrecht}%
\author[1]{Dagmar Kubistin}%
\author[2]{Christian Plass-Dulmer}%
\author[3]{David W. Tarasick}%
\author[3]{Jonathan Davies}%
\author[4]{Peter von der Gathen}%
\author[5]{Holger Deckelmann}%
\author[6]{Nis Jepsen}%
\author[7]{Rigel Kivi}%
\author[8]{Norrie Lyall}%
\author[9]{Mathias Palm}%
\author[10]{Justus Notholt}%
\author[11]{Bogumil Kois}%
\author[1]{Peter Oelsner}%
\author[12]{Marc Allaart}%
\author[12]{Ankie Piters}%
\author[13]{Michael Gill}%
\author[14]{Roeland Van Malderen}%
\author[14]{Andy Delcloo}%
\author[15]{Ralf Sussmann}%
\author[16]{Christian Servais}%
\author[16]{Emmanuel Mahieu}%
\author[17]{Gonzague Romanens}%
\author[18]{René Stübi}%
\author[19]{Gerard Ancellet}%
\author[19]{Sophie Godin-Beekmann}%
\author[20]{Shoma Yamanouchi}%
\author[20]{Kimberly Strong}%
\author[21]{Bryan J. J. Johnson}%
\author[22]{Patrick Cullis}%
\author[23]{Irina Petropavlovskikh}%
\author[24]{James W Hannigan}%
\author[25]{Jose-Luis Hernandez}%
\author[25]{Ana Diaz Rodriguez}%
\author[26]{Tatsumi Nakano}%
\author[27]{Thierry Leblanc}%
\author[27]{Fernando Chouza}%
\author[28]{Carlos Torres}%
\author[28]{Omaira García}%
\author[29]{Amelie Röhling}%
\author[29]{Matthias Schneider}%
\author[29]{Thomas Blumenstock}%
\author[30]{Matthew Brian Tully}%
\author[31]{Clare Paton-Walsh}%
\author[31]{Nicholas Brian Jones}%
\author[32]{Richard Querel}%
\author[33]{Susan E Strahan}%
\author[34]{Antje Inness}%
\author[34]{Richard J. Engelen}%
\author[35]{Kai-Lan Chang}%
\author[36]{Owen R. R. Cooper}%
\author[37]{Ryan Michael Stauffer}%
\author[38]{Anne M. Thompson}%
\affil[1]{Deutscher Wetterdienst}%
\affil[2]{Deutscher Wetterdienst, Meteorologisches Observatorium}%
\affil[3]{Environment and Climate Change Canada}%
\affil[4]{Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research}%
\affil[5]{Alfred Wegener Institute for Polar and Marine Research}%
\affil[6]{Danish Meteorological Institute}%
\affil[7]{Finnish Meteorological Institute}%
\affil[8]{UK Met Office}%
\affil[9]{University of Bremen}%
\affil[10]{Institute of Environmental Physics, University of Bremen}%
\affil[11]{Institute of Meteorology and Water Management}%
\affil[12]{Royal Netherlands Meteorological Institute}%
\affil[13]{Met Éireann (Irish Met. Service)}%
\affil[14]{Royal Meteorological Institute of Belgium}%
\affil[15]{Karlsruhe Institute of Technology, IMK-IFU}%
\affil[16]{University of Liège}%
\affil[17]{MeteoSwiss}%
\affil[18]{Federal Office of Meteorology and Climatology, MeteoSwiss}%
\affil[19]{LATMOS, CNRS, UVSQ, UPMC}%
\affil[20]{University of Toronto}%
\affil[21]{NOAA  ESRL}%
\affil[22]{NOAA ESRL}%
\affil[23]{Cooperative Institude for Research in Environmental Sciences, CU}%
\affil[24]{National Center for Atmospheric Research (UCAR)}%
\affil[25]{Agencia Estatal de Meteorología (AEMET)}%
\affil[26]{Japan Meteorological Agency}%
\affil[27]{Jet Propulsion Laboratory, California Institute of Technology}%
\affil[28]{Agencia Estatal de Meteorología (AEMET), CIAI}%
\affil[29]{Karlsruhe Institute of Technology, IMK-ASF}%
\affil[30]{Bureau of Meteorology}%
\affil[31]{University of Wollongong}%
\affil[32]{National Institute of Water \& Atmospheric Research (NIWA)}%
\affil[33]{Universities Space Research Association}%
\affil[34]{ECMWF}%
\affil[35]{Earth System Research Laboratory}%
\affil[36]{Earth System Reserach Laboratory NOAA}%
\affil[37]{NASA Goddard Space Flight Center}%
\affil[38]{NASA-GODDARD}%


\vspace{-1em}



  
  \date{May 16, 2024}


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\selectlanguage{english}
\begin{abstract}
Throughout spring and summer 2020, ozone stations in the northern
extratropics recorded unusually low ozone in the free troposphere. From
April to August, and from 1 to 8 kilometers altitude, ozone was on
average 7\% (\textasciitilde{}4 ppbv) below the 2000 to 2020
climatological mean. Such low ozone, over several months, and at so many
stations, has not been observed in any previous year since at least
2000. Atmospheric composition re-analyses from the Copernicus Atmosphere
Monitoring Service and simulations from the NASA GMI model indicate that
the large 2020 springtime ozone depletion in the Arctic stratosphere has
contributed less than one quarter to the observed tropospheric anomaly.
The observed anomaly is consistent with two recent model simulations,
which assume emission reductions similar to those caused by the COVID-19
crisis. COVID-19 related emission reductions appear to be the major
cause for the observed low free tropospheric ozone in 2020.%
\end{abstract}%



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