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@ARTICLE{Afchine:852457,
      author       = {Afchine, Armin and Rolf, Christian and Costa, Anja and
                      Spelten, Nicole and Riese, Martin and Buchholz, Bernhard and
                      Ebert, Volker and Heller, Romy and Kaufmann, Stefan and
                      Minikin, Andreas and Voigt, Christiane and Zöger, Martin
                      and Smith, Jessica and Lawson, Paul and Lykov, Alexey and
                      Khaykin, Sergey and Krämer, Martina},
      title        = {{I}ce particle sampling from aircraft – influence of the
                      probing position on the ice water content},
      journal      = {Atmospheric measurement techniques},
      volume       = {11},
      number       = {7},
      issn         = {1867-8548},
      address      = {Katlenburg-Lindau},
      publisher    = {Copernicus},
      reportid     = {FZJ-2018-05403},
      pages        = {4015 - 4031},
      year         = {2018},
      abstract     = {The ice water content (IWC) of cirrus clouds is an
                      essential parameter determining their radiative properties
                      and thus is important for climate simulations. Therefore,
                      for a reliable measurement of IWC on board research
                      aircraft, it is important to carefully design the ice
                      crystal sampling and measuring devices. During the ML-CIRRUS
                      field campaign in 2014 with the German Gulfstream GV HALO
                      (High Altitude and Long Range Research Aircraft), IWC was
                      recorded by three closed-path total water together with one
                      gas-phase water instrument. The hygrometers were supplied by
                      inlets mounted on the roof of the aircraft fuselage.
                      Simultaneously, the IWC is determined by a cloud particle
                      spectrometer attached under an aircraft wing. Two more
                      examples of simultaneous IWC measurements by hygrometers and
                      cloud spectrometers are presented, but the inlets of the
                      hygrometers were mounted at the fuselage side (M-55
                      Geophysica, StratoClim campaign 2017) and bottom (NASA WB57,
                      MacPex campaign 2011). This combination of instruments and
                      inlet positions provides the opportunity to experimentally
                      study the influence of the ice particle sampling position on
                      the IWC with the approach of comparative measurements. As
                      expected from theory and shown by computational fluid
                      dynamics (CFD) calculations, we found that the IWCs provided
                      by the roof inlets deviate from those measured under the
                      aircraft wing. As a result of the inlet position in the
                      shadow zone behind the aircraft cockpit, ice particle
                      populations with mean mass sizes larger than about 25µm
                      radius are subject to losses, which lead to strongly
                      underestimated IWCs. On the other hand, cloud populations
                      with mean mass sizes smaller than about 12µm are dominated
                      by particle enrichment and thus overestimated IWCs. In the
                      range of mean mass sizes between 12 and 25µm, both
                      enrichment and losses of ice crystals can occur, depending
                      on whether the ice crystal mass peak of the size
                      distribution – in these cases bimodal – is on the
                      smaller or larger mass mode. The resulting deviations of the
                      IWC reach factors of up to 10 or even more for losses as
                      well as for enrichment. Since the mean mass size of ice
                      crystals increases with temperature, losses are more
                      pronounced at higher temperatures, while at lower
                      temperatures IWC is more affected by enrichment. In
                      contrast, in the cases where the hygrometer inlets were
                      mounted at the fuselage side or bottom, the agreement of
                      IWCs is most frequently within a factor of 2.5 or better –
                      due to less disturbed ice particle sampling, as expected
                      from theory – independently of the mean ice crystal sizes.
                      The rather large scatter between IWC measurements reflects,
                      for example, cirrus cloud inhomogeneities and instrument
                      uncertainties as well as slight sampling biases which might
                      also occur on the side or bottom of the fuselage and under
                      the wing. However, this scatter is in the range of other
                      studies and represent the current best possible IWC
                      recording on fast-flying aircraft.},
      cin          = {IEK-7},
      ddc          = {550},
      cid          = {I:(DE-Juel1)IEK-7-20101013},
      pnm          = {244 - Composition and dynamics of the upper troposphere and
                      middle atmosphere (POF3-244)},
      pid          = {G:(DE-HGF)POF3-244},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000438287600002},
      doi          = {10.5194/amt-11-4015-2018},
      url          = {https://juser.fz-juelich.de/record/852457},
}