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@ARTICLE{Podglajen:885398,
      author       = {Podglajen, Aurelien and Hertzog, Albert and Plougonven,
                      Riwal and Legras, Bernard},
      title        = {{L}agrangian gravity wave spectra in the lower stratosphere
                      of current (re)analyses},
      journal      = {Atmospheric chemistry and physics},
      volume       = {20},
      number       = {15},
      issn         = {1680-7324},
      address      = {Katlenburg-Lindau},
      publisher    = {EGU},
      reportid     = {FZJ-2020-03795},
      pages        = {9331 - 9350},
      year         = {2020},
      abstract     = {Due to their increasing spatial resolution, numerical
                      weather prediction (NWP) models and the associated analyses
                      resolve a growing fraction of the gravity wave (GW)
                      spectrum. However, it is unclear how well this
                      “resolved” part of the spectrum truly compares to the
                      actual atmospheric variability. In particular, the
                      Lagrangian variability, relevant, for example, to
                      atmospheric dispersion and to microphysical modeling in the
                      upper troposphere–lower stratosphere (UTLS), has not yet
                      been documented in recent products.To address this
                      shortcoming, this paper presents an assessment of the GW
                      spectrum as a function of the intrinsic (air parcel
                      following) frequency in recent (re)analyses (ERA-Interim,
                      ERA5, the ECMWF operational analysis and MERRA-2).
                      Long-duration, quasi-Lagrangian balloon observations in the
                      equatorial and Antarctic lower stratosphere are used as a
                      reference for the atmospheric spectrum and are compared to
                      synthetic balloon observations along trajectories calculated
                      using the wind and temperature fields of the reanalyses.
                      Overall, the reanalyses represent realistic features of the
                      spectrum, notably the spectral gap between planetary and
                      gravity waves and a peak in horizontal kinetic energy
                      associated with inertial waves near the Coriolis frequency f
                      in the polar region. In the tropics, they represent the
                      slope of the spectrum at low frequency. However, the
                      variability is generally underestimated even in the
                      low-frequency portion of the spectrum. In particular, the
                      near-inertial peak, although present in the reanalyses, has
                      a reduced magnitude compared to balloon observations. We
                      compare the observed and modeled variabilities of
                      temperature, zonal momentum flux and vertical wind speed,
                      which are related to low-, mid- and high-frequency waves,
                      respectively. The probability density function (PDF)
                      distributions have similar shapes but show increasing
                      disagreement with increasing intrinsic frequency. Since at
                      those altitudes they are mainly caused by gravity waves, we
                      also compare the geographic distribution of vertical wind
                      fluctuations in the different products, which emphasizes the
                      increase of both GW variance and intermittency with
                      horizontal resolution. Finally, we quantify the fraction of
                      resolved variability and its dependency on model resolution
                      for the different variables. In all (re)analysis products, a
                      significant part of the variability is still missing,
                      especially at high frequencies, and should hence be
                      parameterized. Among the two polar balloon datasets used,
                      one was broadcast on the Global Telecommunication System for
                      assimilation in NWP models, while the other consists of
                      independent observations (unassimilated in the reanalyses).
                      Comparing the Lagrangian spectra between the two campaigns
                      shows that the (re)analyses are largely influenced by
                      balloon data assimilation, which especially enhances the
                      variance at low GW frequency.},
      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:000562089000001},
      doi          = {10.5194/acp-20-9331-2020},
      url          = {https://juser.fz-juelich.de/record/885398},
}