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@ARTICLE{Smit:59857,
      author       = {Smit, H. G. J. and Volz-Thomas, A. and Helten, M. and
                      Pätz, H.-W. and Kley, D.},
      title        = {{A}n in-flight {C}alibration {M}ethod for
                      {N}ear-{R}eal-{T}ime {H}umidity {M}easurements with the
                      {A}irborne {MOZAIC} sensor},
      journal      = {Journal of atmospheric and oceanic technology},
      volume       = {25},
      issn         = {0739-0572},
      address      = {Boston, Mass.},
      publisher    = {AMS},
      reportid     = {PreJuSER-59857},
      pages        = {656 - 666},
      year         = {2008},
      note         = {Record converted from VDB: 12.11.2012},
      abstract     = {A new in-flight calibration (IFC) method is described for
                      the humidity sensor flown routinely since 1994 on the
                      Measurement of Ozone and Water Vapor by Airbus In-Service
                      Aircraft (MOZAIC) program's aircraft. The IFC method
                      corrects the potential drift of the sensor offset at zero
                      relative humidity, which is the critical parameter in
                      determining the uncertainty of the measurements. The sensor
                      offset is determined from the measurements themselves as
                      obtained during periods when the aircraft is flying in the
                      lower stratosphere at or above the hygropause, where the H2O
                      mixing ratio reaches well-defined minimum values of about 5
                      ppmv and the contribution of atmospheric H2O to the sensor
                      signal is minimal. The selection of stratospheric data is
                      achieved with the help of potential temperature, which can
                      be calculated in situ from measured temperature and
                      pressure. The IFC method is capable of providing humidity
                      measurements in near-real time with an uncertainty of
                      $+/-8\%$ RH at the surface and $+/-7\%$ RH in the upper
                      troposphere.For validation, the IFC method was applied to 5
                      yr of archived raw signals from the MOZAIC aircraft. The
                      resulting humidity data are in good agreement (within $2\%$
                      RH) with the original MOZAIC data that used monthly pre- and
                      postflight calibrations of the sensor. The standard
                      deviation of the differences varies with altitude between
                      $+/-4\%$ and $+/-6\%$ RH, which is comparable to the
                      accuracy of the MOZAIC laboratory calibrations. Compared to
                      MOZAIC operation based on monthly calibrations in the
                      laboratory, the use of IFC will substantially reduce the
                      efforts for maintenance and thus will enable operation of
                      the sensor on a large fleet of in-service aircraft for
                      near-real-time measurements of humidity in the troposphere.
                      Because the IFC method will not work on aircraft that never
                      enter the lower stratosphere, for example, aircraft that fly
                      exclusively regional routes or in the tropics, regular
                      offline calibrations will remain important for such
                      aircraft.},
      keywords     = {J (WoSType)},
      cin          = {ICG-2},
      ddc          = {550},
      cid          = {I:(DE-Juel1)VDB791},
      pnm          = {Atmosphäre und Klima},
      pid          = {G:(DE-Juel1)FUEK406},
      shelfmark    = {Engineering, Ocean / Meteorology $\&$ Atmospheric Sciences},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000256069000002},
      doi          = {10.1175/2007JTECHA975.1},
      url          = {https://juser.fz-juelich.de/record/59857},
}