Geosci. Model Dev., 5, 193–221, 2012 www.geosci-model-dev.net/5/193/2012/ Geoscientific doi:10.5194/gmd-5-193-2012 Model Development © Author(s) 2012. CC Attribution 3.0 License. A Lagrangian model of air-mass photochemistry and mixing using a trajectory ensemble: the Cambridge Tropospheric Trajectory model of Chemistry And Transport (CiTTyCAT) version 4.2 T. A. M. Pugh1, M. Cain2, J. Methven3, O. Wild1, S. R. Arnold4, E. Real5, K. S. Law6, K. M. Emmerson4,*, S. M. Owen7, J. A. Pyle2, C. N. Hewitt1, and A. R. MacKenzie1,** 1Lancaster Environment Centre, Lancaster University, Lancaster, UK 2Department of Chemistry, University of Cambridge, Cambridge, UK 3Department of Meteorology, University of Reading, Reading, UK 4Institute for Climate and Atmospheric Science, School of Earth and Environment, University of Leeds, Leeds, UK 5CEREA, Joint Laboratory Ecole des Ponts ParisTech/EDF R&D, Universite´ Paris-Est, 77455 – Champs sur Marne, France 6UPMC Univ. Paris 06, Univ. Versailles St-Quentin, CNRS/INSU, LATMOS-IPSL, Paris, France 7Centre for Ecology and Hydrology, Edinburgh, UK *now at: CSIRO Marine and Atmospheric Research, Aspendale, VIC 3195, Australia **now at: School of Geography, Earth and Environmental Science, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK Correspondence to: A. R. MacKenzie (
[email protected]) Received: 31 August 2011 – Published in Geosci. Model Dev. Discuss.: 27 September 2011 Revised: 19 January 2012 – Accepted: 20 January 2012 – Published: 31 January 2012 Abstract. A Lagrangian model of photochemistry and mix- air-masses can persist for many days while stretching, fold- ing is described (CiTTyCAT, stemming from the Cambridge ing and thinning.