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@ARTICLE{Kloss:862204,
      author       = {Kloss, Corinna and von Hobe, Marc and Höpfner, M. and
                      Kaley, A. and Walker, K. A. and Riese, Martin and Ungermann,
                      Jörn and Hassler, B. and Kremser, St. and Bodeker, G. E.},
      title        = {{S}ampling bias adjustment for sparsely sampled satellite
                      measurements applied to {ACE}-{FTS} carbonyl sulfide
                      observations},
      journal      = {Atmospheric measurement techniques},
      volume       = {12},
      number       = {4},
      issn         = {1867-1381},
      address      = {Katlenburg-Lindau},
      publisher    = {Copernicus},
      reportid     = {FZJ-2019-02552},
      pages        = {2129-2138},
      year         = {2019},
      abstract     = {When computing climatological averages of atmospheric
                      trace-gas mixing ratios obtained from satellite-based
                      measurements, sampling biases arise if data coverage is not
                      uniform in space and time. Homogeneous spatiotemporal
                      coverage is essentially impossible to achieve. Solar
                      occultation measurements, by virtue of satellite orbit and
                      the requirement of direct observation of the sun through the
                      atmosphere, result in particularly sparse spatial coverage.
                      In this proof-of-concept study, a method is presented to
                      adjust for such sampling biases when calculating
                      climatological means. The method is demonstrated using
                      carbonyl sulfide (OCS) measurements at 16 km altitude from
                      the ACE-FTS (Atmospheric Chemistry Experiment Fourier
                      Transform Spectrometer). At this altitude, OCS mixing ratios
                      show a steep gradient between the poles and Equator. ACE-FTS
                      measurements, which are provided as vertically resolved
                      profiles, and integrated stratospheric OCS columns are used
                      in this study. The bias adjustment procedure requires no
                      additional information other than the satellite data product
                      itself. In particular, the method does not rely on
                      atmospheric models with potentially unreliable transport or
                      chemistry parameterizations, and the results can be used
                      uncompromised to test and validate such models. It is
                      expected to be generally applicable when constructing
                      climatologies of long-lived tracers from sparsely and
                      heterogeneously sampled satellite measurements. In the first
                      step of the adjustment procedure, a regression model is used
                      to fit a 2-D surface to all available ACE-FTS OCS
                      measurements as a function of day-of-year and latitude. The
                      regression model fit is used to calculate an adjustment
                      factor that is then used to adjust each measurement
                      individually. The mean of the adjusted measurement points of
                      a chosen latitude range and season is then used as the
                      bias-free climatological value. When applying the adjustment
                      factor to seasonal averages in 30∘ zones, the maximum
                      spatiotemporal sampling bias adjustment was $11 \%$ for
                      OCS mixing ratios at 16 km and $5 \%$ for the
                      stratospheric OCS column. The adjustments were validated
                      against the much denser and more homogeneous OCS data
                      product from the limb-sounding MIPAS (Michelson
                      Interferometer for Passive Atmospheric Sounding) instrument,
                      and both the direction and magnitude of the adjustments were
                      in agreement with the adjustment of the ACE-FTS data.},
      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:000463862300001},
      doi          = {10.5194/amt-12-2129-2019},
      url          = {https://juser.fz-juelich.de/record/862204},
}