1. A European Network for Atmospheric Hydrogen observations and studies EUROHYDROS: A European Network for Atmospheric Hydrogen observations and studies Coordination: Andreas Engel and Anja Werner, J.W. Goethe University, Frankfurt Workpackage Coordinators: Ingeborg Levin / Kazimierz Rozanski: WP1 Observations Euan Nisbet / Thomas Roeckmann: WP2 Source/Sink studies Frode Stordal / Martin Schultz: WP 3 Modelling Stefan Reimann / Armin Jordan : WP 4 Calibration and Quality Control

2. A European Network for Atmospheric Hydrogen observations and studies EUROHYDROS: Science Aims Establish a quality controlled network for atmospheric hydrogen observations, using a common scale. Establish observations of H 2 isotopic composition to study source sink budgets. Perform diurnal campaigns to derive local H 2 budgets. Perform studies on sinks and sources, incl. their isotopic composition (e.g. ground sink). Perform model studies to derive emissions (inverse modelling), to study the atmospheric budget (incl. Isotopes) and to predict the impact of possibly enhanced H 2 levels on the atmosphere Overall: Improve the understanding of the atm. H 2 budget

3. A European Network for Atmospheric Hydrogen observations and studies Project Partners List of Partners Participant no.Participant organisation nameWork packages 1 UFRA University of Frankfurt, Institut für Atmosphäre und Umwelt WP1, WP2, WP4, WP5 2 RHULRoyal Holloway, University of LondonWP1, WP2, WP4, WP5 3 UIOUniversitetet i OsloWP3, WP5 4 UHEI-IUPRuprecht-Karls-Universität Heidelberg, Institut für Umweltphysik, WP1, WP2, WP3, WP4, WP5 5 AGH-USTUniversity of Science and Technology, Krakow WP1, WP2, WP4, WP5 6 EMPASwiss Federal Laboratories for Materials Testing and Research WP1, WP2, WP4, WP5 7 FMIFinnish Meteorological Inst.WP1, WP2, WP4 8 CNRS- LSCE Centre National de la Recherche ScientifiqueWP1, WP2, WP3, WP4 9 CEA-LSCEComissariat à lénergie atomiqueWP1, WP2, WP3,WP4 10 UNIURBUniversity of UrbinoWP1, WP4 11 UKMOUnited Kingdom Met OfficeWP3 12 UOBUniversity of BristolWP1, WP4 13 UUUniversity of UtrechtWP2, WP4, WP5 14 UEAUniversity of East AngliaWP1, WP4 15 MPI-BGCMax Planck Institut für BiogeochemieWP2, WP3, WP4, WP5 15 MPI-TMMax Planck Institut für terrestrische Mikrobiologie WP2 18 NILUNorsk institutt for luftforskningWP1, WP4 19 FZJForschungszentrum Jülich, Institut für Chemie und Dynamik der Geosphäre WP3, WP5 20 RCARSResearch Centre for Atmospheric Remote Sensing WP1, WP2, WP4

4. A European Network for Atmospheric Hydrogen observations and studies EUROHYDROS: WP 1, measurements The objective of this work package is to make high quality measurements of H 2 mixing ratios at a number of stations. The list of stations includes background sites, moderately polluted and urban/polluted sites. The stations are distributed over Europe, with an addition of some global sites. We will harmonize the data by referencing all measurements to a common scale and submit the data to a common database.

5. A European Network for Atmospheric Hydrogen observations and studies EUROHYDROS: WP 1, measurements

6. A European Network for Atmospheric Hydrogen observations and studies EUROHYDROS: WP 1, measurements

7. A European Network for Atmospheric Hydrogen observations and studies EUROHYDROS: WP 2, sources and sinks The aims are to improve the understanding of the soil sink by performing soil uptake experiments with flux chambers to investigate dependence on soil parameters (temperature, moisture, composition etc.). Diurnal cycle campaigns will be performed in still anticyclonic conditions, to measure H2 mixing ratios in combination with known flux calibrators (e.g. 222Rn, carbon gases), in selected areas of known character, to derive soil sinks and regional sources directly. Isotopic composition of H2 will be derived for 3 European and 3 global monitoring stations. The isotopic signatures of key processes will be characterised by flux chamber measurements for soil sinks and combustion sources.

8. A European Network for Atmospheric Hydrogen observations and studies EUROHYDROS: WP 3 Modelling The objectives of this workpackage are to use a multi-scale modelling approach to 1.assess the level of understanding of the H2 budget in the present day atmosphere on the global and the European scale and derive sources and sinks based on emission inventories and observed distributions of hydrogen and its isotopic composition 2.assess trends and the seasonal variability of H2 in the stratosphere and troposphere 3.explore the impact of changes in the H2 budget on the oxidising capacity of the troposphere and on the water and ozone balance of the stratosphere

9. A European Network for Atmospheric Hydrogen observations and studies EUROHYDROS: WP 4 Calibration and Quality Control There is currently no internationally-consistent scale for hydrogen. An essential task will be the production, maintenance and propagation of high quality reference standards and the provision of calibration values for the standards maintained at the individual laboratories. A round-robin intercomparison and an intercomparison with the global monitoring networks CMDL and AGAGE are planned. The data management aims at a central data base with primarily reviewed data to be provided via a common protocol. Thus, data will be available for comparison issues within the consortium. Data will be finalized on a yearly basis and will be made publicly available.