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Start Over Author "Piters, Ankie" Topic [sdu.ocean]sciences of the universe [physics]/ocean, atmosphere
6 results on '"Piters, Ankie"'

1. Ground-based validation of the Copernicus Sentinel-5p TROPOMI NO2 measurements with the NDACC ZSL-DOAS, MAX-DOAS and Pandonia global networks

Author

Verhoelst, Tiji, Pinardi, Gala, Eskes, Henk J., Fjæraa, Ann Mari, Boersma, Klaas Folkert, Levelt, Pieternel F., Navarro-Comas, Monica, Piters, Ankie J. M., Sinyakov, Valery P., Strong, Kimberley, Veefkind, Pepijn J., Yela-González, Margarita, Verhoelst, Tijl, Compernolle, Steven, Pinardi, Gaia, Lambert, Jean-Christopher, Eskes, Henk, Eichmann, Kai-Uwe, Fjaeraa, Ann, Granville, José, Niemeijer, Sander, Cede, Alexander, Tiefengraber, Martin, Hendrick, François, Pazmino, Andrea, Bais, Alkiviadis, Bazureau, Ariane, Folkert Boersma, K, Bognar, Kristof, Dehn, Angelika, Donner, Sebastian, Elokhov, Aleksandr, Gebetsberger, Manuel, Goutail, Florence, Grutter de la Mora, Michel, Gruzdev, Aleksandr, Gratsea, Myrto, Hansen, Georg, Irie, Hitoshi, Jepsen, Nis, Kanaya, Yugo, Karagkiozidis, Dimitris, Kivi, Rigel, Kreher, Karin, Levelt, Pieternel, Liu, Cheng, Müller, Moritz, Navarro Comas, Monica, Piters, Ankie, Pommereau, Jean-Pierre, Portafaix, Thierry, Prados-Roman, Cristina, Puentedura, Olga, Querel, Richard, Remmers, Julia, Richter, Andreas, Rimmer, John, Rivera Cárdenas, Claudia, Saavedra De Miguel, Lidia, Sinyakov, Valery, Stremme, Wolfgang, Strong, Kimberly, Van Roozendaël, Michel, Pepijn Veefkind, J, Wagner, Thomas, Wittrock, Folkard, Yela González, Margarita, Zehner, Claus, Belgian Institute for Space Aeronomy / Institut d'Aéronomie Spatiale de Belgique (BIRA-IASB), Royal Netherlands Meteorological Institute (KNMI), Norsk Institutt for Luftforskning (NILU), Meteorology and Air Quality Group, Wageningen University and Research [Wageningen] (WUR), Delft University of Technology (TU Delft), Instituto Nacional de Técnica Aeroespacial (INTA), Kyrgyz National University of Jusup Balasagyn, Department of Physics [Toronto], University of Toronto, BK Scientific GmbH, Institut für Umweltphysik [Bremen] (IUP), Universität Bremen, Science [&] Technology Corporation [Delft] (S [&] T), NASA Goddard Space Flight Center (GSFC), Institute of Meteorology and Geophysics [Innsbruck], University of Innsbruck, STRATO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Laboratory of Atmospheric Physics [Thessaloniki], Aristotle University of Thessaloniki, European Space Research Institute (ESRIN), European Space Agency (ESA), Max-Planck-Institut für Chemie (MPIC), Max-Planck-Gesellschaft, A.M.Obukhov Institute of Atmospheric Physics (IAP), Russian Academy of Sciences [Moscow] (RAS), Centro de Ciencias de la Atmosfera [Mexico], Universidad Nacional Autónoma de México (UNAM), National Observatory of Athens (NOA), Center for Environmental Remote Sensing [Chiba] (CEReS), Chiba University, Danish Meteorological Institute (DMI), Research Institute for Global Change (RIGC), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Space and Earth Observation Centre [Sodankylä], Finnish Meteorological Institute (FMI), Department of Precision Machinery and Precision Instrumentation [Hefei], University of Science and Technology of China [Hefei] (USTC), Laboratoire de l'Atmosphère et des Cyclones (LACy), Centre National de la Recherche Scientifique (CNRS)-Université de La Réunion (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Météo France, National Institute of Water and Atmospheric Research [Lauder] (NIWA), University of Manchester [Manchester], Institute of Environmental Physics [Bremen] (IUP), and University of Bremen

Subjects
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere
Abstract

International audience; This paper reports on consolidated ground-based validation results of the atmospheric NO2 data produced operationally since April 2018 by the TROPOMI instrument on board of the ESA/EU Copernicus Sentinel-5 Precursor (S5p) satellite. Tropospheric, stratospheric, and total NO2 column data from S5p are compared to correlative measurements collected from, respectively, 19 Multi-Axis DOAS (MAX-DOAS), 26 NDACC Zenith-Scattered-Light DOAS (ZSL-DOAS), and 25 PGN/Pandora instruments distributed globally. The validation methodology gives special care to minimizing mismatch errors due to imperfect spatio-temporal co-location of the satellite and correlative data, e.g., by using tailored observation operators to account for differences in smoothing and in sampling of atmospheric structures and variability, and photochemical modelling to reduce diurnal cycle effects. Compared to the ground-based measurements, S5p data show, on an average: (i) a negative bias for the tropospheric column data, of typically −23 to −37 % in clean to slightly polluted conditions, but reaching values as high as −51 % over highly polluted areas; (ii) a slight negative bias for the stratospheric column data, of about −0.2 Pmolec/cm2, i.e. approx. −2 % in summer to −15 % in winter; and (iii) a bias ranging from zero to −50 % for the total column data, found to depend on the amplitude of the total NO2 column, with small to slightly positive bias values for columns below 6 Pmolec/cm2 and negative values above. The dispersion between S5p and correlative measurements contains mostly random components, which remain within mission requirements for the stratospheric column data (0.5 Pmolec/cm2), but exceed those for the tropospheric column data (0.7 Pmolec/cm2). While a part of the biases and dispersion may be due to representativeness differences, it is known that errors in the S5p tropospheric columns exist due to shortcomings in the (horizontally coarse) a-priori profile representation in the TM5-MP chemistry transport model used in the S5p retrieval, and to a lesser extent, to the treatment of cloud effects. Although considerable differences (up to 2 Pmolec/cm2 and more) are observed at single ground-pixel level, the near-real-time (NRTI) and off-line (OFFL) versions of the S5p NO2 operational data processor provide similar NO2 column values and validation results when globally averaged, with the NRTI values being on average 0.79 % larger than the OFFL values.

Published
2021

2. Ground-based validation of the Copernicus Sentinel-5p TROPOMI NO2 measurements with the NDACC ZSL-DOAS, MAX-DOAS and Pandonia global networks

Author

Verhoelst, Tiji, Compernolle, Steven, Pinardi, Gala, Lambert, Jean-Christopher, Eskes, Henk J., Eichmann, Kai-Uwe, Fjæraa, Ann Mari, Granville, José, Niemeijer, Sander, Cede, Alexander, Tiefengraber, Martin, Hendrick, François, Pazmino, Andrea, Bais, Alkiviadis, Bazureau, Ariane, Boersma, Klaas Folkert, Bognar, Kristof, Dehn, Angelika, Donner, Sebastian, Elokhov, Aleksandr, Gebetsberger, Manuel, Goutail, Florence, Grutter de la Mora, Michel, Gruzdev, Aleksandr, Gratsea, Myrto, Hansen, Georg, Irie, Hitoshi, Jepsen, Nis, Kanaya, Yugo, Karagkiozidis, Dimitris, Kivi, Rigel, Kreher, Karin, Levelt, Pieternel F., Liu, Cheng, Müller, Moritz, Navarro-Comas, Monica, Piters, Ankie J. M., Pommereau, Jean-Pierre, Portafaix, Thierry, Puentedura, Olga, Querel, Richard, Remmers, Julia, Richter, Andreas, Rimmer, John, Rivera Cárdenas, Claudia, Saavedra De Miguel, Lidia, Sinyakov, Valery P., Strong, Kimberley, Van Roozendaël, Michel, Veefkind, Pepijn J., Wagner, Thomas, Wittrock, Folkard, Yela-González, Margarita, Zehner, Claus, Belgian Institute for Space Aeronomy / Institut d'Aéronomie Spatiale de Belgique (BIRA-IASB), Royal Netherlands Meteorological Institute (KNMI), Institut für Umweltphysik [Bremen] (IUP), Universität Bremen, Norsk Institutt for Luftforskning (NILU), Science [&] Technology Corporation [Delft] (S [&] T), NASA Goddard Space Flight Center (GSFC), Institute of Meteorology and Geophysics [Innsbruck], University of Innsbruck, STRATO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Laboratory of Atmospheric Physics [Thessaloniki], Aristotle University of Thessaloniki, Meteorology and Air Quality Group, Wageningen University and Research [Wageningen] (WUR), Department of Physics [Toronto], University of Toronto, European Space Research Institute (ESRIN), European Space Agency (ESA), Max-Planck-Institut für Chemie (MPIC), Max-Planck-Gesellschaft, A.M.Obukhov Institute of Atmospheric Physics (IAP), Russian Academy of Sciences [Moscow] (RAS), Centro de Ciencias de la Atmosfera [Mexico], Universidad Nacional Autónoma de México (UNAM), National Observatory of Athens (NOA), Center for Environmental Remote Sensing [Chiba] (CEReS), Chiba University, Danish Meteorological Institute (DMI), Research Institute for Global Change (RIGC), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Space and Earth Observation Centre [Sodankylä], Finnish Meteorological Institute (FMI), BK Scientific GmbH, Delft University of Technology (TU Delft), Department of Precision Machinery and Precision Instrumentation [Hefei], University of Science and Technology of China [Hefei] (USTC), Instituto Nacional de Técnica Aeroespacial (INTA), Laboratoire de l'Atmosphère et des Cyclones (LACy), Météo France-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS), National Institute of Water and Atmospheric Research [Lauder] (NIWA), University of Manchester [Manchester], Kyrgyz National University, Institute of Environmental Physics [Bremen] (IUP), and University of Bremen

Subjects
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere
Abstract

This paper reports on consolidated ground-based validation results of the atmospheric NO2 data produced operationally since April 2018 by the TROPOMI instrument on board of the ESA/EU Copernicus Sentinel-5 Precursor (S5p) satellite. Tropospheric, stratospheric, and total NO2 column data from S5p are compared to correlative measurements collected from, respectively, 19 Multi-Axis DOAS (MAX-DOAS), 26 NDACC Zenith-Scattered-Light DOAS (ZSL-DOAS), and 25 PGN/Pandora instruments distributed globally. The validation methodology gives special care to minimizing mismatch errors due to imperfect spatio-temporal co-location of the satellite and correlative data, e.g., by using tailored observation operators to account for differences in smoothing and in sampling of atmospheric structures and variability, and photochemical modelling to reduce diurnal cycle effects. Compared to the ground-based measurements, S5p data show, on an average: (i) a negative bias for the tropospheric column data, of typically −23 to −37 % in clean to slightly polluted conditions, but reaching values as high as −51 % over highly polluted areas; (ii) a slight negative bias for the stratospheric column data, of about −0.2 Pmolec/cm2, i.e. approx. −2 % in summer to −15 % in winter; and (iii) a bias ranging from zero to −50 % for the total column data, found to depend on the amplitude of the total NO2 column, with small to slightly positive bias values for columns below 6 Pmolec/cm2 and negative values above. The dispersion between S5p and correlative measurements contains mostly random components, which remain within mission requirements for the stratospheric column data (0.5 Pmolec/cm2), but exceed those for the tropospheric column data (0.7 Pmolec/cm2). While a part of the biases and dispersion may be due to representativeness differences, it is known that errors in the S5p tropospheric columns exist due to shortcomings in the (horizontally coarse) a-priori profile representation in the TM5-MP chemistry transport model used in the S5p retrieval, and to a lesser extent, to the treatment of cloud effects. Although considerable differences (up to 2 Pmolec/cm2 and more) are observed at single ground-pixel level, the near-real-time (NRTI) and off-line (OFFL) versions of the S5p NO2 operational data processor provide similar NO2 column values and validation results when globally averaged, with the NRTI values being on average 0.79 % larger than the OFFL values.

Published
2020

3. Intercomparison of NO2, O-4, O-3 and HCHO slant column measurements by MAX-DOAS and zenith-sky UV-visible spectrometers during CINDI-2

Author

Kreher, Karin, Van Roozendael, Michel, Hendrick, Francois, Apituley, Arnoud, Dimitropoulou, Ermioni, Friess, Udo, Richter, Andreas, Wagner, Thomas, Lampel, Johannes, Abuhassan, Nader, Ang, Li, Anguas, Monica, Bais, Alkis, Benavent, Nuria, Boesch, Tim, Bognar, Kristof, Borovski, Alexander, Bruchkouski, Ilya, Cede, Alexander, Chan, Ka Lok, Donner, Sebastian, Drosoglou, Theano, Fayt, Caroline, Finkenzeller, Henning, Garcia-Nieto, David, Gielen, Clio, Gomez-Martin, Laura, Hao, Nan, Henzing, Bas, Herman, Jay R., Hermans, Christian, Hoque, Syedul, Irie, Hitoshi, Jin, Junli, Johnston, Paul, Butt, Junaid Khayyam, Khokhar, Fahim, Koenig, Theodore K., Kuhn, Jonas, Kumar, Vinod, Liu, Cheng, Ma, Jianzhong, Merlaud, Alexis, Mishra, Abhishek K., Mueller, Moritz, Navarro-Comas, Monica, Ostendorf, Mareike, Pazmino, Andrea, Peters, Enno, Pinardi, Gaia, Pinharanda, Manuel, Piters, Ankie, Platt, Ulrich, Postylyakov, Oleg, Prados-Roman, Cristina, Puentedura, Olga, Querel, Richard, Saiz-Lopez, Alfonso, Schoenhardt, Anja, Schreier, Stefan F., Seyler, Andre, Sinha, Vinayak, Spinei, Elena, Strong, Kimberly, Tack, Frederik, Tian, Xin, Tiefengraber, Martin, Tirpitz, Jan-Lukas, van Gent, Jeron, Volkamer, Rainer, Vrekoussis, Mihalis, Wang, Shanshan, Wang, Zhuoru, Wenig, Mark, Wittrock, Folkard, Xie, Pinhua H., Xu, Jin, Yela, Margarita, Zhang, Chengxin, Zhao, Xiaoyi, BK Scientific GmbH, Belgian Institute for Space Aeronomy / Institut d'Aéronomie Spatiale de Belgique (BIRA-IASB), Royal Netherlands Meteorological Institute (KNMI), Institut für Umweltphysik [Heidelberg], Universität Heidelberg [Heidelberg], Institute of Environmental Physics [Bremen] (IUP), University of Bremen, Max-Planck-Institut für Chemie (MPIC), Max-Planck-Gesellschaft, NASA Goddard Space Flight Center (GSFC), Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences [Changchun Branch] (CAS), Instituto de Química Física Rocasolano (IQFR), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Laboratory of Atmospheric Physics [Thessaloniki], Aristotle University of Thessaloniki, Department of Physics [Toronto], University of Toronto, A.M.Obukhov Institute of Atmospheric Physics (IAP), Russian Academy of Sciences [Moscow] (RAS), Belarusian State University, Meteorologisches Institut München (MIM), Ludwig-Maximilians-Universität München (LMU), School of Earth and Space Sciences [Hefei], University of Science and Technology of China [Hefei] (USTC), Department of Chemistry and Biochemistry [Boulder], University of Colorado [Boulder], Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado [Boulder]-National Oceanic and Atmospheric Administration (NOAA), Instituto Nacional de Técnica Aeroespacial (INTA), European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT), The Netherlands Organisation for Applied Scientific Research (TNO), Center for Environmental Remote Sensing [Chiba] (CEReS), Chiba University, Chinese Academy of Meteorological Sciences (CAMS), National Institute of Water and Atmospheric Research [Lauder] (NIWA), National University of Sciences and Technology [Islamabad] (NUST), Institute of Environmental Physics [Heidelberg] (IUP), Indian Institute of Science Education and Research Mohali (IISER Mohali), Department of Earth and Environmental Sciences [Mohali], Department of Atmospheric and Cryospheric Sciences [Innsbruck] (ACINN), Universität Innsbruck [Innsbruck], STRATO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Institute for the Protection of Maritime Infrastructures, Deutsches Zentrum für Luft- und Raumfahrt (DLR), Institute for Meteorology and Climatology [Vienna] (BOKU-Met), University of Natural Resources and Life Sciences (BOKU), Virginia Polytechnic Institute and State University [Blacksburg], Center for Marine Environmental Sciences [Bremen] (MARUM), Universität Bremen, Energy, Environment and Water Research Center (EEWRC), Cyprus Institute (CyI), Liaoning Technical University [Huludao], Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention (LAP3), Fudan University [Shanghai], DLR Institut für Methodik der Fernerkundung / DLR Remote Sensing Technology Institute (IMF), Deutsches Zentrum für Luft- und Raumfahrt [Oberpfaffenhofen-Wessling] (DLR), Environment and Climate Change Canada, and Electrical and Computer Engineering

Subjects
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Science & Technology, RAMAN-SCATTERING, RETRIEVAL, CROSS-SECTIONS, BRO, RADIATIVE-TRANSFER, Physical Sciences, Meteorology & Atmospheric Sciences, OPTICAL-ABSORPTION SPECTROSCOPY, FORMALDEHYDE, CAMPAIGN, NITROGEN-DIOXIDE, AEROSOL EXTINCTION
Abstract

In September 2016, 36 spectrometers from 24 institutes measured a number of key atmospheric pollutants for a period of 17 d during the Second Cabauw Intercomparison campaign for Nitrogen Dioxide measuring Instruments (CINDI-2) that took place at Cabauw, the Netherlands (51.97 degrees N, 4.93 degrees E). We report on the outcome of the formal semi-blind intercomparison exercise, which was held under the umbrella of the Network for the Detection of Atmospheric Composition Change (NDACC) and the European Space Agency (ESA). The three major goals of CINDI-2 were (1) to characterise and better understand the differences between a large number of multi-axis differential optical absorption spectroscopy (MAX-DOAS) and zenith-sky DOAS instruments and analysis methods, (2) to define a robust methodology for performance assessment of all participating instruments, and (3) to contribute to a harmonisation of the measurement settings and retrieval methods. This, in turn, creates the capability to produce consistent high-quality ground-based data sets, which are an essential requirement to generate reliable long-term measurement time series suitable for trend analysis and satellite data validation. The data products investigated during the semi-blind intercomparison are slant columns of nitrogen dioxide (NO2), the oxygen collision complex (O-4) and ozone (O-3) measured in the UV and visible wavelength region, formaldehyde (HCHO) in the UV spectral region, and NO2 in an additional (smaller) wavelength range in the visible region. The campaign design and implementation processes are discussed in detail including the measurement protocol, calibration procedures and slant column retrieval settings. Strong emphasis was put on the careful alignment and synchronisation of the measurement systems, resulting in a unique set of measurements made under highly comparable air mass conditions. The CINDI-2 data sets were investigated using a regression analysis of the slant columns measured by each instrument and for each of the target data products. The slope and intercept of the regression analysis respectively quantify the mean systematic bias and offset of the individual data sets against the selected reference (which is obtained from the median of either all data sets or a subset), and the rms error provides an estimate of the measurement noise or dispersion. These three criteria are examined and for each of the parameters and each of the data products, performance thresholds are set and applied to all the measurements. The approach presented here has been developed based on heritage from previous intercomparison exercises. It introduces a quantitative assessment of the consistency between all the participating instruments for the MAX-DOAS and zenith-sky DOAS techniques. Netherlands Space Office (NSO); ESA through the CINDI-2 (ESA) project [4000118533/16/I-Sbo]; ESA through the FRM4DOAS (ESA) project [4000118181/16/I-EF]; EU 7th Framework Programme QA4ECV projectEuropean Union (EU) [607405]; Austrian Science Fund (FWF)Austrian Science Fund (FWF) [I 2296-N29]; Canadian Space Agency (AVATARS project); Natural Sciences and Engineering Research Council (PAHA project); Canada Foundation for InnovationCanada Foundation for Innovation; UVAS ("Ultraviolet and Visible Atmospheric Sounder") projects SEOSAT/INGENIO [ESP2015-71299-R]; DFG project RAPSODI [PL 193/17-1]; Centre National de la Recherche Scientifique (CNRS)Centre National de la Recherche Scientifique (CNRS); Centre National d'Etudes Spatiales (CNES)Centre National D'etudes Spatiales; National funding project HELADO [CTM2013-41311-P]; National funding project AVATAR [CGL2014-55230-R]; Russian Science FoundationRussian Science Foundation (RSF) [16-17-10275]; Russian Foundation for Basic ResearchRussian Foundation for Basic Research (RFBR) [16-05-01062, 18-35-00682]; ACTRIS-2 (H2020 grant) [654109]; NASA's Atmospheric Composition ProgramNational Aeronautics & Space Administration (NASA) [NASA-16-NUP2016-0001]; US National Science FoundationNational Science Foundation (NSF) [AGS-1620530]; NASANational Aeronautics & Space Administration (NASA); University of Bremen; DFG Research Center/Cluster of Excellence "The Ocean in the Earth System-MARUM"German Research Foundation (DFG); University of Bremen Institutional Strategy of the DFG; Luftblick through the ESA Pandonia Project; NASA Pandora Project at the Goddard Space Flight Center under NASA Headquarters' Tropospheric Composition Program CINDI-2 received funding from the Netherlands Space Office (NSO). Funding for this study was provided by ESA through the CINDI-2 (ESA contract no. 4000118533/16/I-Sbo) and FRM4DOAS (ESA contract no. 4000118181/16/I-EF) projects and partly within the EU 7th Framework Programme QA4ECV project (grant agreement no. 607405). The BOKU MAX-DOAS instrument was funded and the participation of Stefan F. Schreier was supported by the Austrian Science Fund (FWF): I 2296-N29. The participation of the University of Toronto team was supported by the Canadian Space Agency (through the AVATARS project) and the Natural Sciences and Engineering Research Council (through the PAHA project). The instrument was primarily funded by the Canada Foundation for Innovation and is usually operated at the Polar Environment Atmospheric Research Laboratory (PEARL) by the Canadian Network for the Detection of Atmospheric Change (CANDAC). Funding for CISC was provided by the UVAS ("Ultraviolet and Visible Atmospheric Sounder") projects SEOSAT/INGENIO, ESP2015-71299-R, MINECO-FEDER and UE. The activities of the IUP-Heidelberg were supported by the DFG project RAPSODI (grant no. PL 193/17-1). SAOZ and Mini-SAOZ instruments are supported by the Centre National de la Recherche Scientifique (CNRS) and the Centre National d'Etudes Spatiales (CNES). INTA recognises support from the National funding projects HELADO (CTM2013-41311-P) and AVATAR (CGL2014-55230-R). AMOIAP recognises support from the Russian Science Foundation (grant no. 16-17-10275) and the Russian Foundation for Basic Research (grant nos. 16-05-01062 and 18-35-00682). Ka L. Chan received transnational access funding from ACTRIS-2 (H2020 grant agreement no. 654109). Rainer Volkamer recognises funding from NASA's Atmospheric Composition Program (NASA-16-NUP2016-0001) and the US National Science Foundation (award AGS-1620530). Henning Finkenzeller is the recipient of a NASA graduate fellowship. Mihalis Vrekoussis recognises support from the University of Bremen and the DFG Research Center/Cluster of Excellence "The Ocean in the Earth System-MARUM". Financial support through the University of Bremen Institutional Strategy in the framework of the DFG Excellence Initiative is gratefully appreciated for Anja Schonhardt. Pandora instrument deployment was supported by Luftblick through the ESA Pandonia Project and NASA Pandora Project at the Goddard Space Flight Center under NASA Headquarters' Tropospheric Composition Program. The article processing charges for this open-access publication were covered by BK Scientific.

Published
2020

4. Ground-based Assessment of the First Year of Sentinel-5p Tropospheric Ozone Data

Author

Hubert, Daan, Keppen, Arno, Verhoelst, Tijl, Granville, José, Lambert, Jean-Christopher, Heue, Klaus-Peter, Pedergnana, Mattia, Loyola, Diego, Eichmann, Kai-Uwe, Weber, Mark, Apituley, Arnoud, Sneep, Maarten, Tuinder, Olaf, Veefkind, Pepijn, Thompson, Anne, Witte, Jacquelyn, Johnson, Bryan, Vömel, Holger, Selkirk, Henry, Piters, Ankie, Da Silva, Francisco, Mohamad, Maznorizan, Félix, Christian, Ancellet, Gérard, Delcloo, Andy, Duflot, Valentin, Godin-Beekmann, Sophie, Leblanc, Thierry, Steinbrecht, Wolfgang, Stübi, René, Belgian Institute for Space Aeronomy / Institut d'Aéronomie Spatiale de Belgique (BIRA-IASB), DLR Institut für Methodik der Fernerkundung / DLR Remote Sensing Technology Institute (IMF), Deutsches Zentrum für Luft- und Raumfahrt [Oberpfaffenhofen-Wessling] (DLR), Institut für Umweltphysik [Bremen] (IUP), Universität Bremen, Royal Netherlands Meteorological Institute (KNMI), NASA Goddard Space Flight Center (GSFC), Science Systems and Applications, Inc. [Lanham] (SSAI), NOAA Earth System Research Laboratory (ESRL), National Oceanic and Atmospheric Administration (NOAA), National Center for Atmospheric Research [Boulder] (NCAR), Universities Space Research Association (USRA), Laboratory of Environmental and Tropical Variables [Natal], Instituto Nacional de Pesquisas Espaciais (INPE), Malaysian Meteorological Department (MetMalaysia), Ministry of Science, Technology and Innovation [Malaysia] (MOSTI), Federal Office of Meteorology and Climatology MeteoSwiss, TROPO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Institut Royal Météorologique de Belgique [Bruxelles] (IRM), Laboratoire de l'Atmosphère et des Cyclones (LACy), Centre National de la Recherche Scientifique (CNRS)-Université de La Réunion (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Météo France, STRATO - LATMOS, Jet Propulsion Laboratory (JPL), California Institute of Technology (CALTECH)-NASA, Meteorologisches Observatorium Hohenpeißenberg (MOHp), Deutscher Wetterdienst [Offenbach] (DWD), and Cardon, Catherine

Subjects
[PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, [SDU.OCEAN] Sciences of the Universe [physics]/Ocean, Atmosphere, [PHYS.PHYS.PHYS-AO-PH] Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph]
Abstract

International audience; Tropospheric ozone is a pollutant that damages ecosystems and triggers human health problems. Ozone concentrations are highly variable over time and across the troposphere, which poses clear challenges to deepen our understanding of the processes involved in the production and transport of ozone. Further progress depends on the availability of instruments capable of measuring tropospheric ozone and its distribution at finer spatio-temporal scales. The TROPOMI instrument on the Sentinel-5p platform, launched into an early afternoon polar orbit in October 2017, combines a high spatial resolution, a large swath width and the spectral measurement characteristics required to deliver tropospheric ozone data records at unprecedented detail. The first of these products was released during Fall 2018. It consists in 0.5° (latitude) by 1° (longitude) resolved daily maps of 3-day moving mean values of the tropospheric ozone column between 20°S and 20°N, and it is computed using the convective-cloud method (CCD). A second data product consists in maps of tropical upper tropospheric ozone mixing ratio at a coarser spatial and temporal resolution. It is based on a cloud slicing algorithm (CSA), which is currently being fine-tuned for release in the very near future. A third data product, also under development at the time of this abstract, consists of the vertical profile of ozone concentration in the global troposphere and stratosphere, retrieved with the classical Optimal Estimation (OE) technique. We present here an assessment of the quality of the first year of the different tropospheric ozone column data sets retrieved from Sentinel-5p TROPOMI measurements, carried out within the context of ESA’s Sentinel-5p Mission Performance Center (MPC) and the S5PVT AO project CHEOPS-5p (Validation of Copernicus Height-resolved Ozone data Products from Sentinel-5p TROPOMI using global sonde and lidar networks, #28587). The first stage of this analysis consists of an inspection of the tropospheric ozone fields for structures which are potentially introduced in the measurement process. Sampling effects, in particular, are a possible source of uncertainty as the CCD product is derived from binned TROPOMI total ozone column data. Another structure introduced by retrieval assumptions would be the dependence of the quality of Sentinel-5p retrieved total column data to cloud parameters. In a second stage the satellite data are confronted to quality-assured ozonesonde and –tentatively– ground-based lidar measurements from the NDACC, SHADOZ and TOLNET networks. These well-characterized observational data records serve as a reference to evaluate the bias and uncertainty of the Sentinel-5p data, and their dependence on influence quantities. The study concludes with an assessment of the compliance of Sentinel-5p tropospheric ozone data with respect to mission and user requirements for key data applications.

Published
2019

5. Satellite nadir NO2 validation based on zenith-sky, direct-sun and MAXDOAS network observations

Author

Pinardi, Gaia, Van Roozendael, Michel, Lambert, Jean-Christopher, Granville, José, Hendrick, François, Gielen, Clio, Cede, Alexander, Kanaya, Ygo, Irie, Hitoshi, Wittrock, Folkard, Richter, Andreas, Peters, Enno, Wagner, Thomas, Gu, Myojeong, Remmers, Julia, Lampel, Johannes, Friess, Udo, Vlemmix, Tim, Piters, Ankie, Hao, Nan, Tiefengraber, Martin, Herman, Jay, Abuhassan, Nader, Holla, Robert, Bais, Alkis, Balis, Dimitris, Drosoglou, Theano, Kouremeti, Natalia, Hovila, Jari, Chong, J., Postylyakov, Oleg, Ma, Jianzhong, Goutail, Florence, Pommereau, Jean-Pierre, Pazmino, Andrea, Navarro, Monica, Puentedura, Olga, Yu, Huan, Belgian Institute for Space Aeronomy / Institut d'Aéronomie Spatiale de Belgique (BIRA-IASB), NASA Goddard Space Flight Center (GSFC), Research Institute for Global Change (RIGC), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Center for Environmental Remote Sensing [Chiba] (CEReS), Chiba University, Institute of Environmental Physics [Bremen] (IUP), University of Bremen, Max Planck Institute for Chemistry (MPIC), Max-Planck-Gesellschaft, Institut für Umweltphysik [Heidelberg], Universität Heidelberg [Heidelberg], Department of Geoscience and Remote Sensing [Delft], Delft University of Technology (TU Delft), Royal Netherlands Meteorological Institute (KNMI), DLR Institut für Methodik der Fernerkundung / DLR Remote Sensing Technology Institute (IMF), Deutsches Zentrum für Luft- und Raumfahrt [Oberpfaffenhofen-Wessling] (DLR), Institute of Meteorology and Geophysics [Innsbruck], University of Innsbruck, Joint Center for Earth Systems Technology [Baltimore] (JCET), NASA Goddard Space Flight Center (GSFC)-University of Maryland [Baltimore County] (UMBC), University of Maryland System-University of Maryland System, Meteorologisches Observatorium Hohenpeißenberg (MOHp), Deutscher Wetterdienst [Offenbach] (DWD), Laboratory of Atmospheric Physics [Thessaloniki], Aristotle University of Thessaloniki, Physikalisch-Meteorologisches Observatorium Davos/World Radiation Center (PMOD/WRC), Finnish Meteorological Institute (FMI), Gwangju Institute of Science and Technology (GIST), A.M.Obukhov Institute of Atmospheric Physics (IAP), Russian Academy of Sciences [Moscow] (RAS), Chinese Academy of Meteorological Sciences (CAMS), STRATO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Instituto Nacional de Técnica Aeroespacial (INTA), Cardon, Catherine, Universität Heidelberg [Heidelberg] = Heidelberg University, and Leopold Franzens Universität Innsbruck - University of Innsbruck

Subjects
[PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, [SDU.OCEAN] Sciences of the Universe [physics]/Ocean, Atmosphere, [PHYS.PHYS.PHYS-AO-PH] Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph]
Abstract

International audience; Since more than fifteen years, total and tropospheric NO2 columns have been retrieved from nadir space-borne sensors such as SCIAMACHY on ENVISAT, OMI on AURA and GOME-2 on MetOp platforms. The NO2 data products are generally retrieved in three main steps: (1) a DOAS spectral analysis yielding the total column amount of NO2 along the slant optical path, (2) an estimation of the stratospheric NO2 column, to be subtracted from the total column to derive the tropospheric contribution, and (3) a conversion of the total and tropospheric slant columns into vertical columns based on airmass factor calculations which require a-priori knowledge of the NO2 vertical distribution and surface albedo, as well as information on cloud cover and height.In this study we combine correlative measurements available from several ground-based remote sensing networks to address the validation of (1) the GOME-2 GDP 4.8 NO2 products generated within the EUMETSAT O3M-SAF project, and (2) the SCIAMACHY, OMI and GOME-2 TEMIS product. Zenith-sky DOAS/SAOZ measurements from the NDACC network are used to assess the stratospheric NO2 columns retrieved from the satellite, while the consistency of the total and tropospheric NO2 columns in urban, sub-urban and back-ground conditions is investigated using direct-sun Pandora and multi-axis MAXDOAS data sets from about 40 stations. Where available, vertical profile information from MAXDOAS measurements is used to assess the reliability of the different satellite a-priori profile shapes.Results are discussed in terms of observed biases between satellite and ground-based data sets, their dependence on location, season and cloud conditions. For stratospheric columns, the uncertainty related to the correction applied for ensuring the photochemical matching between satellite and ground-based observations is also evaluated. The satellite pixels resolution effect is statistically explored in relation to the typical extent of the emission sources at urban site locations, using data from SCIAMACHY 60x30 km², GOME-2 40x80 km² and OMI 13x24 km².

Published
2016

6. COVID‐19 Crisis Reduces Free Tropospheric Ozone Across the Northern Hemisphere

Author

Marc Allaart, Susan E. Strahan, Ryan M. Stauffer, Richard Querel, Anne M. Thompson, Nicholas B. Jones, Clare Paton-Walsh, Patrick Cullis, Tatsumi Nakano, Bryan J. Johnson, Gérard Ancellet, Thomas Blumenstock, Ankie Piters, Holger Deckelmann, Omaira García, Matthias Palm, Roeland Van Malderen, Kai-Lan Chang, Nis Jepsen, Antje Inness, M.B. Tully, Ralf Sussmann, Amelie N. Röhling, Gonzague Romanens, Dagmar Kubistin, Ana Diaz Rodriguez, Fernando Chouza, René Stübi, Owen R. Cooper, Emmanuel Mahieu, Kimberly Strong, Christian Plass-Dülmer, Jonathan Davies, Richard Engelen, Peter Oelsner, David W. Tarasick, Peter von der Gathen, Jose-Luis Hernandez, Michael Gill, Justus Notholt, Thierry Leblanc, Christian Servais, Irina Petropavlovskikh, Matthias Schneider, Norrie Lyall, Rigel Kivi, Carlos Torres, Shoma Yamanouchi, Sophie Godin-Beekmann, Bogumil Kois, James W. Hannigan, Wolfgang Steinbrecht, Andy Delcloo, Deutscher Wetterdienst [Offenbach] (DWD), Environment and Climate Change Canada, Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung (AWI), Danish Meteorological Institute (DMI), Finnish Meteorological Institute (FMI), Met Office Lerwick, Universität Bremen, Institute of Meteorology and Water Management - National Research Institute (IMGW - PIB), Royal Netherlands Meteorological Institute (KNMI), Irish Meteorological Service (MET ÉIREANN), Institut Royal Météorologique de Belgique [Bruxelles] (IRM), Institut für Meteorologie und Klimaforschung - Atmosphärische Umweltforschung (IMK-IFU), Karlsruher Institut für Technologie (KIT), Institut d'Astrophysique et de Géophysique [Liège], Université de Liège, Federal Office of Meteorology and Climatology MeteoSwiss, TROPO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), STRATO - LATMOS, University of Toronto, ESRL Global Monitoring Laboratory [Boulder] (GML), NOAA Earth System Research Laboratory (ESRL), National Oceanic and Atmospheric Administration (NOAA)-National Oceanic and Atmospheric Administration (NOAA), Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado [Boulder]-National Oceanic and Atmospheric Administration (NOAA), National Center for Atmospheric Research [Boulder] (NCAR), Agencia Estatal de Meteorología (AEMet), Meteorological Research Institute [Tsukuba] (MRI), Japan Meteorological Agency (JMA), Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), Institut für Meteorologie und Klimaforschung - Atmosphärische Spurengase und Fernerkundung (IMK-ASF), Australian Bureau of Meteorology [Melbourne] (BoM), Australian Government, University of Wollongong [Australia], National Institute of Water and Atmospheric Research [Lauder] (NIWA), GSFC Earth Sciences Division, NASA Goddard Space Flight Center (GSFC), Earth Science System Interdisciplinary Center [College Park] (ESSIC), College of Computer, Mathematical, and Natural Sciences [College Park], University of Maryland [College Park], University of Maryland System-University of Maryland System-University of Maryland [College Park], University of Maryland System-University of Maryland System, European Centre for Medium-Range Weather Forecasts (ECMWF), NOAA Chemical Sciences Laboratory (CSL), National Oceanic and Atmospheric Administration (NOAA), University of Wollongong, GFSC Earth Sciences Division, Kubistin, Dagmar, 1 Deutscher Wetterdienst Hohenpeißenberg Germany, Plass‐Dülmer, Christian, Davies, Jonathan, 2 Environment and Climate Change Canada Toronto ONT Canada, Tarasick, David W., Gathen, Peter von der, 3 Alfred Wegener Institut Helmholtz‐Zentrum für Polar‐ und Meeresforschung Potsdam Germany, Deckelmann, Holger, Jepsen, Nis, 4 Danish Meteorological Institute Copenhagen Denmark, Kivi, Rigel, 5 Finnish Meteorological Institute Sodankylä Finland, Lyall, Norrie, 6 British Meteorological Service Lerwick UK, Palm, Matthias, 7 University of Bremen Bremen Germany, Notholt, Justus, Kois, Bogumil, 8 Institute of Meteorology and Water Management Legionowo Poland, Oelsner, Peter, 9 Deutscher Wetterdienst Lindenberg Germany, Allaart, Marc, 10 Royal Netherlands Meteorological Institute DeBilt The Netherlands, Piters, Ankie, Gill, Michael, 11 Met Éireann (Irish Met. Service) Valentia Ireland, Van Malderen, Roeland, 12 Royal Meteorological Institute of Belgium Uccle Belgium, Delcloo, Andy W., Sussmann, Ralf, 13 Karlsruhe Institute of Technology IMK‐IFU Garmisch‐Partenkirchen Germany, Mahieu, Emmanuel, 14 Institute of Astrophysics and Geophysics University of Liège Liège Belgium, Servais, Christian, Romanens, Gonzague, 15 Federal Office of Meteorology and Climatology MeteoSwiss Payerne Switzerland, Stübi, Rene, Ancellet, Gerard, 16 LATMOS Sorbonne Université‐UVSQ‐CNRS/INSU Paris France, Godin‐Beekmann, Sophie, Yamanouchi, Shoma, 17 University of Toronto Toronto ONT Canada, Strong, Kimberly, Johnson, Bryan, 18 NOAA ESRL Global Monitoring Laboratory Boulder CO USA, Cullis, Patrick, Petropavlovskikh, Irina, Hannigan, James W., 20 National Center for Atmospheric Research Boulder CO USA, Hernandez, Jose‐Luis, 21 State Meteorological Agency (AEMET) Madrid Spain, Diaz Rodriguez, Ana, Nakano, Tatsumi, 22 Meteorological Research Institute Tsukuba Japan, Chouza, Fernando, 23 Jet Propulsion Laboratory California Institute of Technology Table Mountain Facility Wrightwood CA USA, Leblanc, Thierry, Torres, Carlos, 24 Izaña Atmospheric Research Center AEMET Tenerife Spain, Garcia, Omaira, Röhling, Amelie N., 25 Karlsruhe Institute of Technology IMK‐ASF Karlsruhe Germany, Schneider, Matthias, Blumenstock, Thomas, Tully, Matt, 26 Bureau of Meteorology Melbourne Australia, Paton‐Walsh, Clare, 27 Centre for Atmospheric Chemistry University of Wollongong Wollongong Australia, Jones, Nicholas, Querel, Richard, 28 National Institute of Water and Atmospheric Research Lauder New Zealand, Strahan, Susan, 29 NASA Goddard Space Flight Center Earth Sciences Division Greenbelt MD USA, Stauffer, Ryan M., Thompson, Anne M., Inness, Antje, 32 European Centre for Medium‐Range Weather Forecasts Reading UK, Engelen, Richard, Chang, Kai‐Lan, 19 Cooperative Institute for Research in Environmental Sciences (CIRES) University of Colorado Boulder CO USA, and Cooper, Owen R.

Subjects
Atmospheric Science, 010504 meteorology & atmospheric sciences, Pollution: Urban, Regional and Global, Atmospheric Composition and Structure, Biogeosciences, 010502 geochemistry & geophysics, Atmospheric sciences, [SDV.MHEP.PSR]Life Sciences [q-bio]/Human health and pathology/Pulmonology and respiratory tract, 01 natural sciences, Biogeochemical Kinetics and Reaction Modeling, LIDAR, Troposphere, Oceanography: Biological and Chemical, chemistry.chemical_compound, [SDV.MHEP.MI]Life Sciences [q-bio]/Human health and pathology/Infectious diseases, Emission reductions, ddc:550, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, VERTICAL-DISTRIBUTION, Marine Pollution, RECORD, NOX, 551.51, Biogeochemistry, Ozone depletion, Oceanography: General, Pollution: Urban and Regional, Geophysics, Free troposphere, Emissions, Troposphere: Composition and Chemistry, The COVID‐19 pandemic: linking health, society and environment, Cryosphere, Biogeochemical Cycles, Processes, and Modeling, Ozone, Megacities and Urban Environment, URBAN, Atmosphere, Paleoceanography, Altitude, COVID‐19, Research Letter, Global Change, Tropospheric ozone, Stratosphere, Urban Systems, 0105 earth and related environmental sciences, Aerosols, [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], emissions, Northern Hemisphere, COVID-19, PROFILES, Aerosols and Particles, TRENDS, Earth sciences, ozone, Physics and Astronomy, troposphere, chemistry, 13. Climate action, General Earth and Planetary Sciences, Environmental science, Natural Hazards
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% (≈4 nmol/mol) below the 2000–2020 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 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 contributed less than one‐quarter of the observed tropospheric anomaly. The observed anomaly is consistent with recent chemistry‐climate model simulations, which assume emissions reductions similar to those caused by the COVID‐19 crisis. COVID‐19 related emissions reductions appear to be the major cause for the observed reduced free tropospheric ozone in 2020., Plain Language Summary: Worldwide actions to contain the COVID‐19 virus have closed factories, grounded airplanes, and have generally reduced travel and transportation. Less fuel was burnt, and less exhaust was emitted into the atmosphere. Due to these measures, the concentration of nitrogen oxides and volatile organic compounds (VOCs) decreased in the atmosphere. These substances are important for photochemical production and destruction of ozone in the atmosphere. In clean or mildly polluted air, reducing nitrogen oxides and/or VOCs will reduce the photochemical production of ozone and result in less ozone. In heavily polluted air, in contrast, reducing nitrogen oxides can increase ozone concentrations, because less nitrogen oxide is available to destroy ozone. In this study, we use data from three types of ozone instruments, but mostly from ozonesondes on weather balloons. The sondes fly from the ground up to 30 kilometers altitude. In the first 8 km, we find significantly reduced ozone concentrations in the northern extratropics during spring and summer of 2020, less than in any other year since at least 2000. We suggest that reduced emissions due to the COVID‐19 crisis have lowered photochemical ozone production and have caused the observed ozone reductions in the troposphere., Key Points: In spring and summer 2020, stations in the northern extratropics report on average 7% (4 nmol/mol) less tropospheric ozone than normal Such low tropospheric ozone, over several months, and at so many sites, has not been observed in any previous year since at least 2000 Most of the reduction in tropospheric ozone in 2020 is likely due to emissions reductions related to the COVID‐19 pandemic, NASA | Earth Sciences Division (NASA Earth Science Division) http://dx.doi.org/10.13039/100014573, Gouvernement du Canada | Natural Sciences and Engineering Research Council of Canada (NSERC) http://dx.doi.org/10.13039/501100000038, Australian Research Council, Fonds De La Recherche Scientifique ‐ FNRS (FNRS) http://dx.doi.org/10.13039/501100002661, Deutsche Forschungsgemeinschaft (DFG) http://dx.doi.org/10.13039/501100001659, Bundesministerium für Wirtschaft und Energie (BMWi) http://dx.doi.org/10.13039/501100006360

Published
2021

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