Atmos. Chem. Phys., 14, 1055-1073, 2014
© Author(s) 2014. This work is distributed
under the Creative Commons Attribution 3.0 License.
Nitric acid trihydrate nucleation and denitrification in the Arctic stratosphere
J.-U. Grooß1, I. Engel1,2, S. Borrmann3,4, W. Frey4,*, G. Günther1, C. R. Hoyle2,5, R. Kivi6, B. P. Luo2, S. Molleker3, T. Peter2, M. C. Pitts7, H. Schlager8, G. Stiller9, H. Vömel10, K. A. Walker11, and R. Müller1
1Institut für Energie- und Klimaforschung – Stratosphäre (IEK-7), Forschungszentrum Jülich, Germany
2Institute for Atmospheric and Climate Science, ETH Zurich, Zurich, Switzerland
3Institut für Physik der Atmosphäre, Johannes-Gutenberg-Universität Mainz, Germany
4Abteilung Partikelchemie, Max Planck Institut für Chemie, Mainz, Germany
5Paul Scherrer Institute, Villigen, Switzerland
6Finnish Meteorological Institute, Sodankylä, Finnland
7NASA Langley Research Center, Hampton, VA, USA
8Institut für Physik der Atmosphäre, Deutsches Zentrum für Luft- und Raumfahrt, Oberpfaffenhofen, Germany
9Institute for Meteorology and Climate Research, Karlsruhe Institute of Technology, Karlsruhe, Germany
10Meteorological Observatory Lindenberg, Deutscher Wetterdienst, Germany
11Department of Physics, University of Toronto, Ontario, Canada
*now at: School of Earth Sciences, The University of Melbourne, Melbourne, Australia

Abstract. Nitric acid trihydrate (NAT) particles in the polar stratosphere have been shown to be responsible for vertical redistribution of reactive nitrogen (NOy). Recent observations by Cloud–Aerosol Lidar with Orthogonal Polarization (CALIOP) aboard the CALIPSO satellite have been explained in terms of heterogeneous nucleation of NAT on foreign nuclei, revealing this to be an important formation pathway for the NAT particles. In state of the art global- or regional-scale models, heterogeneous NAT nucleation is currently simulated in a very coarse manner using a constant, saturation-independent nucleation rate. Here we present first simulations for the Arctic winter 2009/2010 applying a new saturation-dependent parametrisation of heterogeneous NAT nucleation rates within the Chemical Lagrangian Model of the Stratosphere (CLaMS). The simulation shows good agreement of chemical trace species with in situ and remote sensing observations. The simulated polar stratospheric cloud (PSC) optical properties agree much better with CALIOP observations than those simulated with a constant nucleation rate model. A comparison of the simulated particle size distributions with observations made using the Forward Scattering Spectrometer Probe (FSSP) aboard the high altitude research aircraft Geophysica, shows that the model reproduces the observed size distribution, except for the very largest particles above 15 μm diameter. The vertical NOy redistribution caused by the sedimentation of the NAT particles, in particular the denitrification and nitrification signals observed by the ACE-FTS satellite instrument and the in situ SIOUX instrument aboard the Geophysica, are reproduced by the improved model, and a small improvement with respect to the constant nucleation rate model is found.

Citation: Grooß, J.-U., Engel, I., Borrmann, S., Frey, W., Günther, G., Hoyle, C. R., Kivi, R., Luo, B. P., Molleker, S., Peter, T., Pitts, M. C., Schlager, H., Stiller, G., Vömel, H., Walker, K. A., and Müller, R.: Nitric acid trihydrate nucleation and denitrification in the Arctic stratosphere, Atmos. Chem. Phys., 14, 1055-1073, doi:10.5194/acp-14-1055-2014, 2014.
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