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@ARTICLE{Molleker:185592,
      author       = {Molleker, S. and Borrmann, S. and Schlager, H. and Luo, B.
                      and Frey, W. and Klingebiel, M. and Weigel, R. and Ebert, M.
                      and Mitev, V. and Matthey, R. and Woiwode, W. and Oelhaf, H.
                      and Dörnbrack, A. and Stratmann, G. and Grooß, J.-U. and
                      Günther, G. and Vogel, B. and Müller, R. and Krämer, M.
                      and Meyer, J. and Cairo, F.},
      title        = {{M}icrophysical properties of synoptic-scale polar
                      stratospheric clouds: in situ measurements of unexpectedly
                      large {HNO}3-containing particles in the {A}rctic vortex},
      journal      = {Atmospheric chemistry and physics},
      volume       = {14},
      number       = {19},
      issn         = {1680-7324},
      address      = {Katlenburg-Lindau},
      publisher    = {EGU},
      reportid     = {FZJ-2014-07018},
      pages        = {10785 - 10801},
      year         = {2014},
      abstract     = {In January 2010 and December 2011, synoptic-scale polar
                      stratospheric cloud (PSC) fields were probed during seven
                      flights of the high-altitude research aircraft M-55
                      Geophysica within the RECONCILE (Reconciliation of essential
                      process parameters for an enhanced predictability of Arctic
                      stratospheric ozone loss and its climate interaction) and
                      the ESSenCe (ESSenCe: ESA Sounder Campaign) projects.
                      Particle size distributions in a diameter range between 0.46
                      and 40μm were recorded by four different optical in situ
                      instruments. Three of these particle instruments are based
                      on the detection of forward-scattered light by single
                      particles. The fourth instrument is a grayscale optical
                      array imaging probe. Optical particle diameters of up to
                      35μm were detected with particle number densities and total
                      particle volumes exceeding previous Arctic measurements.
                      Also, gas-phase and particle-bound NOy was measured, as well
                      as water vapor concentrations. The optical characteristics
                      of the clouds were measured by the remote sensing lidar MAL
                      (Miniature Aerosol Lidar) and by the in situ backscatter
                      sonde MAS (Multiwavelength Aerosol Scatterometer), showing
                      the synoptic scale of the encountered PSCs. The particle
                      mode below 2μm in size diameter has been identified as
                      supercooled ternary solution (STS) droplets. The PSC
                      particles in the size range above 2μm in diameter are
                      considered to consist of nitric acid hydrates, and the
                      particles' high HNO3 content was confirmed by the NOy
                      instrument. Assuming a particle composition of nitric acid
                      trihydrate (NAT), the optically measured size distributions
                      result in particle-phase HNO3 mixing ratios exceeding
                      available stratospheric values. Therefore the measurement
                      uncertainties concerning probable overestimations of
                      measured particle sizes and volumes are discussed in detail.
                      We hypothesize that either a strong asphericity or an
                      alternate particle composition (e.g., water ice coated with
                      NAT) could explain our observations. In particular, with
                      respect to the denitrification by sedimentation of large
                      HNO3-containing particles, generally considered to be NAT,
                      our new measurements raise questions concerning composition,
                      shape and nucleation pathways. Answering these would improve
                      the numerical simulation of PSC microphysical processes like
                      cloud particle formation, growth and denitrification, which
                      is necessary for better predictions of future polar ozone
                      losses, especially under changing global climate conditions.
                      Generally, it seems that the occurrence of large NAT
                      particles – sometimes termed "NAT rocks" – are a regular
                      feature of synoptic-scale PSCs in the Arctic.},
      cin          = {IEK-7},
      ddc          = {550},
      cid          = {I:(DE-Juel1)IEK-7-20101013},
      pnm          = {234 - Composition and Dynamics of the Upper Troposphere and
                      Stratosphere (POF2-234)},
      pid          = {G:(DE-HGF)POF2-234},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000344164800025},
      doi          = {10.5194/acp-14-10785-2014},
      url          = {https://juser.fz-juelich.de/record/185592},
}