12 Jul 2021

12 Jul 2021

Review status: this preprint is currently under review for the journal ACP.

Overview: On the transport and transformation of pollutants in the outflow of major population centres – observational data from the EMeRGe European intensive operational period in summer 2017

M. Dolores Andrés Hernández1, Andreas Hilboll2,, Helmut Ziereis3, Eric Förster4, Ovid O. Krüger5, Katharina Kaiser6,7, Johannes Schneider7, Francesca Barnaba8, Mihalis Vrekoussis2,18, Jörg Schmidt9, Heidi Huntrieser3, Anne-Marlene Blechschmidt1, Midhun George1, Vladyslav Nenakhov1,a, Theresa Klausner3, Bruna A. Holanda5, Jennifer Wolf3, Lisa Eirenschmalz3, Marc Krebsbach10, Mira L. Pöhlker5, Anna B. Hedegaard2, Linlu Mei1, Klaus Pfeilsticker11, Yangzhuoran Liu1, Ralf Koppmann10, Hans Schlager3, Birger Bohn12, Ulrich Schumann3, Andreas Richter1, Benjamin Schreiner11, Daniel Sauer3, Robert Baumann3, Mariano Mertens3, Patrick Jöckel3, Markus Kilian3, Greta Stratmann3,b, Christopher Pöhlker5, Monica Campanelli8, Marco Pandolfi13, Michael Sicard14,15, Jose L. Gomez-Amo16, Manuel Pujadas17, Katja Bigge11, Flora Kluge11, Anja Schwarz9, Nikos Daskalakis2, David Walter5, Andreas Zahn4, Ulrich Pöschl5, Harald Bönisch4, Stephan Borrmann6,7, Ulrich Platt11, and John Phillip Burrows1 M. Dolores Andrés Hernández et al.
  • 1Institute of Environmental Physics, University of Bremen, Bremen, Germany
  • 2Laboratory for Modeling and Observation of the Earth System, Institute of Environmental Physics, Bremen, Germany
  • 3Deutsches Zentrum für Luft- und Raumfahrt (DLR), Institut für Physik der Atmosphäre, Oberpfaffenhofen, Germany
  • 4Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research, Karlsruhe, Germany
  • 5Multiphase Chemistry Department, Max Planck Institute for Chemistry, Mainz, Germany
  • 6Institute for Atmospheric Physics, Johannes Gutenberg University, Mainz, Germany
  • 7Particle Chemistry Department, Max Planck Institute for Chemistry, Mainz, Germany
  • 8National Research Council of Italy, Institute of Atmospheric Sciences and Climate (CNR-ISAC), Roma, Italy
  • 9Leipzig Institute for Meteorology, Leipzig University, Leipzig, Germany
  • 10Institute for Atmospheric and Environmental Research, University of Wuppertal, Wuppertal Germany
  • 11Institute for Environmental Physics, University of Heidelberg, Heidelberg, Germany
  • 12Institute of Energy and Climate Research IEK-8, Forschungszentrum Jülich, Jülich, Germany
  • 13Institute of Environmental Assessment and Water Research, Barcelona, Spain
  • 14CommSensLab, Dept. of Signal Theory and Communications, Universitat Politècnica de Catalunya, Barcelona, Spain
  • 15Ciències i Tecnologies de l’Espai-Centre de Recerca de l’Aeronàutica i de l’Espai/Institut d’Estudis Espacials de Catalunya ), Universitat Politècnica de Catalunya Barcelona, Spain
  • 16Dept. Earth Physics and Thermodynamics, University of Valencia, Burjassot, Spain
  • 17Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (Ciemat), Madrid, Spain
  • 18Climate and Atmosphere Research Center (CARE-C), The Cyprus Institute, Nicosia, Cyprus
  • anow at: Flight Experiments, Deutsches Zentrum für Luft- und Raumfahrt (DLR), Oberpfaffenhofen, Germany
  • bnow at: Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany
  • deceased

Abstract. EMeRGe (Effect of Megacities on the transport and transformation of pollutants on the Regional to Global scales) is an international project focusing on atmospheric chemistry, dynamics and transport of local and regional pollution originating in megacities and other major population centres (MPCs). Airborne measurements, taking advantage of the long range capabilities of the HALO research platform (High Altitude and Long range research aircraft,, are a central part of the research project. In order to provide an adequate set of measurements at different spatial scales, two field experiments were positioned in time and space to contrast situations when the photochemical transformation of plumes emerging from MPCs is large. These experiments were conducted in summer 2017 over Europe and in the inter-monsoon period over Asia in spring 2018. The intensive observational periods (IOP) involved HALO airborne measurements of ozone and its precursors, volatile organic compounds, aerosol particles and related species as well as coordinated ground-based ancillary observations at different sites. Perfluorocarbon (PFC) tracer releases and model forecasts supported the flight planning and the identification of pollution plumes.

This paper describes the experimental deployment of the IOP in Europe, which comprised 7 HALO research flights with aircraft base in Oberpfaffenhofen (Germany) for a total of 53 flight hours. The MPC targets London (Great Britain), Benelux/Ruhr area (Belgium, The Netherlands, Luxembourg and Germany), Paris (France), Rome and Po Valley (Italy), Madrid and Barcelona (Spain) were investigated. An in-flight comparison of HALO with the collaborating UK-airborne platform FAAM took place to assure accuracy and comparability of the instrumentation on-board.

Generally, significant enhancement of trace gases and aerosol particles are attributed to emissions originating in MPCs at distances of hundreds of kilometres from the sources. The proximity of different MPCs over Europe favours the mixing of plumes of different origin and level of processing and hampers the unambiguous attribution of the MPC sources. Similarly, urban plumes mix efficiently with natural sources as desert dust and with biomass burning emissions from vegetation and forest fires. This confirms the importance of wildland fire emissions in Europe and indicates an important but discontinuous contribution to the European emission budget that might be of relevance in the design of efficient mitigation strategies.

The synergistic use and consistent interpretation of observational data sets of different spatial and temporal resolution (e.g. from ground-based networks, airborne campaigns, and satellite measurements) supported by modelling within EMeRGe, provides a unique insight to test the current understanding of MPC pollution outflows. The present work provides an overview of the most salient results and scientific questions in the European context, these being addressed in more detail within additional dedicated EMeRGe studies. The deployment and results obtained in Asia will be the subject of separate publications.

M. Dolores Andrés Hernández et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-500', Anonymous Referee #1, 13 Aug 2021
  • RC2: 'Comment on acp-2021-500', Anonymous Referee #2, 10 Oct 2021

M. Dolores Andrés Hernández et al.

M. Dolores Andrés Hernández et al.


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Short summary
EMeRGe provides a unique set of in-situ and remote sensing airborne measurements of trace gases and aerosol particles along selected flight routes in the lower troposphere over Europe. The interpretation uses also complementary collocated ground-based and satellite measurements. The collected data help to improve the current understanding of the complex spatial distribution of trace gases and aerosol particles resulting from mixing, transport and transformation of pollution plumes over Europe.