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@ARTICLE{Strube:884800,
      author       = {Strube, Cornelia and Ern, Manfred and Preusse, Peter and
                      Riese, Martin},
      title        = {{R}emoving spurious inertial instability signals from
                      gravity wave temperature perturbations using spectral
                      filtering methods},
      journal      = {Atmospheric measurement techniques},
      volume       = {13},
      number       = {9},
      issn         = {1867-8548},
      address      = {Katlenburg-Lindau},
      publisher    = {Copernicus},
      reportid     = {FZJ-2020-03262},
      pages        = {4927 - 4945},
      year         = {2020},
      abstract     = {Gravity waves are important drivers of dynamic processes in
                      particular in the middle atmosphere. To analyse atmospheric
                      data for gravity wave signals, it is essential to separate
                      gravity wave perturbations from atmospheric variability due
                      to other dynamic processes. Common methods to separate
                      small-scale gravity wave signals from a large-scale
                      background are separation methods depending on filters in
                      either the horizontal or vertical wavelength domain.
                      However, gravity waves are not the only process that could
                      lead to small-scale perturbations in the atmosphere.
                      Recently, concerns have been raised that vertical wavelength
                      filtering can lead to misinterpretation of other wave-like
                      perturbations, such as inertial instability effects, as
                      gravity wave perturbations.In this paper we assess the
                      ability of different spectral background removal approaches
                      to separate gravity waves and inertial instabilities using
                      artificial inertial instability perturbations, global model
                      data and satellite observations. We investigate a horizontal
                      background removal (which applies a zonal wavenumber filter
                      with additional smoothing of the spectral components in
                      meridional and vertical direction), a sophisticated filter
                      based on 2D time–longitude spectral analysis (see Ern et
                      al., 2011) and a vertical wavelength Butterworth
                      filter.Critical thresholds for the vertical wavelength and
                      zonal wavenumber are analysed. Vertical filtering has to cut
                      deep into the gravity wave spectrum in order to remove
                      inertial instability remnants from the perturbations (down
                      to 6 km cutoff wavelength). Horizontal filtering, however,
                      removes inertial instability remnants in global model data
                      at wavenumbers far lower than the typical gravity wave
                      scales for the case we investigated. Specifically, a cutoff
                      zonal wavenumber of 6 in the stratosphere is sufficient to
                      eliminate inertial instability structures. Furthermore, we
                      show that for infrared limb-sounding satellite profiles it
                      is possible as well to effectively separate perturbations of
                      inertial instabilities from those of gravity waves using a
                      cutoff zonal wavenumber of 6. We generalize the findings of
                      our case study by examining a 1-year time series of SABER
                      (Sounding of the Atmosphere using Broadband Emission
                      Radiometry) 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:000574778900002},
      doi          = {10.5194/amt-13-4927-2020},
      url          = {https://juser.fz-juelich.de/record/884800},
}