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@ARTICLE{Ern:1006441,
      author       = {Ern, Manfred and Diallo, Mohamadou A. and Khordakova, Dina
                      and Krisch, Isabell and Preusse, Peter and Reitebuch, Oliver
                      and Ungermann, Jörn and Riese, Martin},
      title        = {{T}he {QBO} and global-scale tropical waves in {A}eolus
                      wind observations, radiosonde data, and reanalyses},
      reportid     = {FZJ-2023-01675},
      year         = {2023},
      abstract     = {The quasi-biennial oscillation (QBO) of the stratospheric
                      tropical winds influences the global circulation over a wide
                      range of latitudes and altitudes. Although it has strong
                      effects on surface weather and climate, climate models have
                      large difficulties in simulating a realistic QBO, especially
                      in the lower stratosphere. Therefore, global wind
                      observations in the tropical upper troposphere and lower
                      stratosphere (UTLS) are of particular interest for
                      investigating the QBO and the tropical waves that contribute
                      significantly to its driving. In our work, we focus on the
                      years 2018–2022 and investigate the QBO and different
                      tropical wave modes in the UTLS region using global wind
                      observations by the Aeolus satellite instrument, and three
                      meteorological reanalyses (ERA-5, JRA-55, and MERRA-2).
                      Further, we compare these data with observations of selected
                      radiosonde stations. By comparison with Aeolus observations,
                      we find that on zonal average the QBO in the lower
                      stratosphere is well represented in all three reanalyses,
                      with ERA-5 performing best. Averaged over the years
                      2018–2022, agreement between Aeolus and the reanalyses is
                      better than 1 to 2 m s−1, with somewhat larger differences
                      during some periods. Different from zonal averages,
                      radiosonde stations provide only local observations and are
                      therefore biased by global-scale tropical waves, which
                      limits their use as a QBO standard. While reanalyses perform
                      well on zonal average, there can be considerable local
                      biases between reanalyses and radiosondes. We also find
                      that, in the tropical UTLS, zonal wind variances of
                      stationary waves and the most prominent global-scale
                      traveling equatorial wave modes, such as Kelvin waves,
                      Rossby-gravity waves, and equatorial Rossby waves, are in
                      good agreement between Aeolus and all three reanalyses (in
                      most cases better than 20 $\%$ of the peak values in the
                      UTLS). On zonal average, this supports the use of reanalyses
                      as a reference for comparison with free-running climate
                      models, while locally certain biases exist, particularly in
                      the QBO wind shear zones, and around the 2019–2020 QBO
                      disruption.},
      cin          = {IEK-7},
      cid          = {I:(DE-Juel1)IEK-7-20101013},
      pnm          = {2112 - Climate Feedbacks (POF4-211) / DFG project 429838442
                      - Wie wirken sich natürliche Variabilität und anthropogen
                      bedingte Änderungen auf die stratosphärische Brewer-Dobson
                      Zirkulation und den Ozonfluss in die Troposphäre aus?
                      (429838442)},
      pid          = {G:(DE-HGF)POF4-2112 / G:(GEPRIS)429838442},
      typ          = {PUB:(DE-HGF)25},
      doi          = {10.5194/egusphere-2023-408},
      url          = {https://juser.fz-juelich.de/record/1006441},
}