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The Pan-European Gas-AeroSOls-climate interaction Study

The goal of the PEGASOS-project is to better understand the interactions of the anthropogenic and biogenic components of the atmosphere w.r.t. to their impact on air quality on the one hand and on climate on the other. Here, the many non-linear coherences between the various processes are difficult to handle. A concise overview of the atmosphere's chemistry can only be obtained when all mechanisms and species are taken into account, like anthropogenic emissions, biosphere-atmosphere exchange, climate, and transport and chemical conversion of atmospheric trace-gases and aerosols.

Under the project PEGASOS a Zeppelin was converted into a flying measurement platform to allow for high resolution in-situ observations of a list of air pollutants. These measurements shall serve to enhance the basic understanding of air chemistry and the physico-chemichal processes in the atmosphere.

The first part of the campaign takes place in May 2012 over the Netherlands, followed by a southbound trip to Italy's Po-valley until mid July. The second part will be a two-month trip from Friedrichshafen to Finnland in spring 2013.

RIU's contribution to this project consists of two parts that have been conducted in close colaboration with the Institute for Energy and Climate Research - 8 (IEK-8, troposphere) of Research Centre Jülich:


  • High resolution forecasts of a selection of parameters for campaign guidance
    The Chemistry-Transport-Model EURAD-IM is used to compute daily 72-hour-forecasts on a grid with 1km resolution for the current area of interest that can be modified on demand. The list of parameters not only contains meteorological values like temperature, humidity, or horizontal wind-speed, or chemical concetrations for gas-phase and aerosol constituents, but also a set of special details like e.g. reaction rates for chemical reactions or photolysis or characterization plots for certain regimes. This forecast is presented on the PEGASOS - ForecastBrowser.
  • Assimilation of the derived information using 4Dvar with EURAD-IM
    Making use of the technique of four-dimensional variational data assimilation (4Dvar) the gathered measurements are taken to gain information on sources of pollutants as well as on the general chemical state of the atmosphere within the model domain. Furthermore, so called retro-plumes can be generated to get information on where certain pollutants or their precursors have their origin.