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@ARTICLE{Diallo:904129,
      author       = {Diallo, Mohamadou and Ern, Manfred and Ploeger, Felix},
      title        = {{T}he advective {B}rewer–{D}obson circulation in the
                      {ERA}5 reanalysis: climatology, variability, and trends},
      journal      = {Atmospheric chemistry and physics},
      volume       = {21},
      number       = {10},
      issn         = {1680-7316},
      address      = {Katlenburg-Lindau},
      publisher    = {EGU},
      reportid     = {FZJ-2021-05699},
      pages        = {7515 - 7544},
      year         = {2021},
      abstract     = {The stratospheric Brewer–Dobson circulation (BDC) is an
                      important element of climate as it determines the transport
                      and distributions of key radiatively active atmospheric
                      trace gases, which affect the Earth's radiation budget and
                      surface climate.Here, we evaluate the interannual
                      variability, climatology, and trends of the BDC in the ERA5
                      reanalysis and intercompare them with its predecessor, the
                      ERA-Interim reanalysis, for the 1979–2018 period. We also
                      assess the modulation of the circulation by the
                      Quasi-Biennial Oscillation (QBO) and the El Niño–Southern
                      Oscillation (ENSO), as well as the forcings of the
                      circulation by the planetary and gravity wave drag. The
                      comparison of ERA5 and ERA-Interim reanalyses shows a very
                      good agreement in the morphology of the BDC and in its
                      structural modulations by the natural variability related to
                      QBO and ENSO. Despite the good agreement in the spatial
                      structure, there are substantial and significant differences
                      in the strength of the BDC and natural variability impacts
                      on the BDC between the two reanalyses, particularly in the
                      upper troposphere and lower stratosphere (UTLS) and in the
                      upper stratosphere. Throughout most regions of the
                      stratosphere, the variability and trends of the advective
                      BDC are stronger in the ERA5 reanalysis due to stronger
                      planetary and gravity wave forcings, except in the UTLS
                      below 20 km where the tropical upwelling is up to
                      $40 \%$ weaker mainly due to a significantly weaker
                      gravity wave forcing at the equatorial-ward upper flank of
                      the subtropical jet. In the extratropics, the large-scale
                      downwelling is stronger in ERA5 than in ERA-Interim that is
                      linked to significant differences in planetary and gravity
                      wave forcings in the upper stratosphere. Analysis of the BDC
                      trend shows a global insignificant acceleration of the
                      annual mean residual circulation with an acceleration rate
                      of about $1.5 \% decade−1$ at 70 hPa due to the
                      long-term intensification in gravity and planetary wave
                      breaking, consistent with observed and modelled BDC
                      changes.Our findings suggest that the advective BDC from the
                      kinematic ERA5 reanalysis is well suited for climate model
                      validation in the UTLS and mid-stratosphere when using the
                      standard formula of zonally averaged zonal momentum
                      equation. The reported differences between the two
                      reanalyses may also affect the nudged climate model
                      simulations. Therefore, additional studies are needed to
                      investigate whether or not nudging climate models toward
                      ERA5 reanalysis will reproduce the upwelling trends from
                      free-running simulations and from ERA5. Finally, further
                      studies are also needed to better understand the impact of
                      the new non-orographic gravity wave parameterization scheme,
                      higher model top, and the representation of the sponge layer
                      in ERA5 on the differences in the upper stratosphere and
                      polar regions.},
      cin          = {IEK-7},
      ddc          = {550},
      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?},
      pid          = {G:(DE-HGF)POF4-2112 / G:(GEPRIS)429838442},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000653621700005},
      doi          = {10.5194/acp-21-7515-2021},
      url          = {https://juser.fz-juelich.de/record/904129},
}