{"references": ["Karl, M. (2018) Development of the city-scale chemistry transport model CityChem-EPISODE and its application to the city of Hamburg, Geosci. Model Dev. Discuss., https://doi.org/10.5194/gmd-2018-8, 2018.", "Sl\u00f8rdal, L.H., Walker, S.-E., and Solberg, S. (2003) The Urban Air Dispersion Model EPISODE applied in AirQUIS. Technical Description. NILU TR 12/2003. ISBN 82-425-1522-0.", "Sl\u00f8rdal, L.H., McInnes, H., Krognes, T. (2008) The Air Quality Information System AirQUIS. Info. Techn. Environ. Eng., 1, 40-47, 2008.", "Karl, M. Walker, S.-E., Solberg, S., and Ramacher, M. O. P. (2019) The Eulerian urban dispersion model EPISODE. Part II: Extensions to the source dispersion and photochemistry for EPISODE-CityChem and its application to the city of Hamburg, Geosci. Model Dev., https://doi.org/10.5194/gmd-2018-325, in review, 2019."]}

The CityChem extension, developed at Helmholtz-Zentrum Geesthacht (HZG) is designed for treating complex atmospheric chemistry in urban areas and improved representation of the near-field dispersion (Karl et al., 2019). The model is an extension of the EPISODE dispersion model to enable chemistry/transport simulations of reactive pollutants on city scale. EPISODE is an Eulerian dispersion model developed at the Norwegian Institute for Air Research (NILU) appropriate for air quality studies at the local scale (Slørdal et al., 2003; Slørdal et al., 2008). The EPISODE model and the CityChem extension are open source code subject to the Reciprocal Public License ("RPL") Version 1.5, https://opensource.org/licenses/RPL-1.5.

Britt Ann Høisker (NILU) is thanked for permission to distribute the CityChem extension to the EPISODE model under the RPL license. This work was partially funded by the ERA-PLANET trans-national project SMURBS (SMart URBan Solutions for air quality, disasters and city growth), Grant Agreement n. 689443, under the EU Horizon 2020 Framework Programme.