% IMPORTANT: The following is UTF-8 encoded.  This means that in the presence
% of non-ASCII characters, it will not work with BibTeX 0.99 or older.
% Instead, you should use an up-to-date BibTeX implementation like “bibtex8” or
% “biber”.

@ARTICLE{Weigel:280305,
      author       = {Weigel, R. and Spichtinger, P. and Mahnke, C. and
                      Klingebiel, M. and Afchine, Armin and Petzold, Andreas and
                      Krämer, Martina and Costa, Anja and Molleker, S. and
                      Jurkat, T. and Minikin, A. and Borrmann, S.},
      title        = {{T}hermodynamic correction of particle concentrations
                      measured by underwing probes on fast flying aircraft},
      journal      = {Atmospheric measurement techniques discussions},
      volume       = {8},
      issn         = {1867-8610},
      address      = {Katlenburg-Lindau},
      publisher    = {Copernicus},
      reportid     = {FZJ-2016-00094},
      pages        = {13423-13469},
      year         = {2015},
      abstract     = {Particle concentration measurements with underwing probes
                      on aircraft are impacted by air compression upstream of the
                      instrument body as a function of flight velocity. In
                      particular for fast-flying aircraft the necessity arises to
                      account for compression of the air sample volume. Hence, a
                      correction procedure is needed to invert measured particle
                      number concentrations to ambient conditions that is commonly
                      applicable for different instruments to gain comparable
                      results. In the compression region where the detection of
                      particles occurs (i.e. under factual measurement
                      conditions), pressure and temperature of the air sample are
                      increased compared to ambient (undisturbed) conditions in
                      certain distance away from the aircraft. Conventional
                      procedures for scaling the measured number densities to
                      ambient conditions presume that the particle penetration
                      speed through the instruments' detection area equals the
                      aircraft speed (True Air Speed, TAS). However, particle
                      imaging instruments equipped with pitot-tubes measuring the
                      Probe Air Speed (PAS) of each underwing probe reveal PAS
                      values systematically below those of the TAS. We conclude
                      that the deviation between PAS and TAS is mainly caused by
                      the compression of the probed air sample. From measurements
                      during two missions in 2014 with the German Gulfstream G-550
                      (HALO – High Altitude LOng range) research aircraft we
                      develop a procedure to correct the measured particle
                      concentration to ambient conditions using a thermodynamic
                      approach. With the provided equation the corresponding
                      concentration correction factor ξ is applicable to the high
                      frequency measurements of each underwing probe which is
                      equipped with its own air speed sensor (e.g. a pitot-tube).
                      ξ-values of 1 to 0.85 are calculated for air speeds (i.e.
                      TAS) between 60 and 260 m s−1. From HALO data it is found
                      that ξ does not significantly vary between the different
                      deployed instruments. Thus, for the current HALO underwing
                      probe configuration a parameterisation of ξ as a function
                      of TAS is provided for instances if PAS measurements are
                      lacking. The ξ-correction yields higher ambient particle
                      concentration by about 15–25 $\%$ compared to conventional
                      procedures – an improvement which can be considered as
                      significant for many research applications. The calculated
                      ξ-values are specifically related to the considered HALO
                      underwing probe arrangement and may differ for other
                      aircraft or instrument geometries. Moreover, the
                      ξ-correction may not cover all impacts originating from
                      high flight velocities and from interferences between the
                      instruments and, e.g., the aircraft wings and/or fuselage.
                      Consequently, it is important that PAS (as a function of
                      TAS) is individually measured by each probe deployed
                      underneath the wings of a 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) / HITEC - Helmholtz
                      Interdisciplinary Doctoral Training in Energy and Climate
                      Research (HITEC) (HITEC-20170406)},
      pid          = {G:(DE-HGF)POF3-244 / G:(DE-Juel1)HITEC-20170406},
      typ          = {PUB:(DE-HGF)16},
      doi          = {10.5194/amtd-8-13423-2015},
      url          = {https://juser.fz-juelich.de/record/280305},
}