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@ARTICLE{Diallo:862051,
      author       = {Diallo, Mohamadou and Konopka, Paul and Santee, Michelle L.
                      and Müller, Rolf and Tao, Mengchu and Walker, Kaley A. and
                      Legras, Bernard and Riese, Martin and Ern, Manfred and
                      Ploeger, Felix},
      title        = {{S}tructural changes in the shallow and transition branch
                      of the {B}rewer–{D}obson circulation induced by {E}l
                      {N}iño},
      journal      = {Atmospheric chemistry and physics},
      volume       = {19},
      number       = {1},
      issn         = {1680-7324},
      address      = {Katlenburg-Lindau},
      publisher    = {EGU},
      reportid     = {FZJ-2019-02417},
      pages        = {425 - 446},
      year         = {2019},
      abstract     = {The stratospheric Brewer–Dobson circulation (BDC)
                      determines the transport and atmospheric lifetime of key
                      radiatively active trace gases and further impacts surface
                      climate through downward coupling. Here, we quantify the
                      variability in the lower stratospheric BDC induced by the El
                      Niño–Southern Oscillation (ENSO), using satellite trace
                      gas measurements and simulations with the Lagrangian
                      chemistry transport model, CLaMS, driven by ERA-Interim and
                      JRA-55 reanalyses. We show that despite discrepancies in the
                      deseasonalized ozone (O3) mixing ratios between CLaMS
                      simulations and satellite observations, the patterns of
                      changes in the lower stratospheric O3 anomalies induced by
                      ENSO agree remarkably well over the 2005–2016 period.
                      Particularly during the most recent El Niño in 2015–2016,
                      both satellite observations and CLaMS simulations show the
                      largest negative tropical O3 anomaly in the record.
                      Regression analysis of different metrics of the BDC
                      strength, including mean age of air, vertical velocity,
                      residual circulation, and age spectrum, shows clear evidence
                      of structural changes in the BDC in the lower stratosphere
                      induced by El Niño, consistent with observed O3 anomalies.
                      These structural changes during El Niño include a weakening
                      of the transition branch of the BDC between about 370 and
                      420 K (∼100–70 hPa) and equatorward of about 60∘
                      and a strengthening of the shallow branch at the same
                      latitudes and between about 420 and 500 K
                      (∼70–30 hPa). The slowdown of the transition branch is
                      due to an upward shift in the dissipation height of the
                      large-scale and gravity waves, while the strengthening of
                      the shallow branch results mainly from enhanced gravity wave
                      breaking in the tropics–subtropics combined with enhanced
                      planetary wave breaking at high latitudes. The strengthening
                      of the shallow branch induces negative tropical O3 anomalies
                      due to enhanced tropical upwelling, while the weakening of
                      the transition branch combined with enhanced downwelling due
                      to the strengthening shallow branch leads to positive O3
                      anomalies in the extratropical upper troposphere–lower
                      stratosphere (UTLS). Our results suggest that a shift in the
                      ENSO basic state toward more frequent El Niño-like
                      conditions in a warmer future climate will substantially
                      alter UTLS trace gas distributions due to these changes in
                      the vertical structure of the stratospheric circulation.},
      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:000455810000001},
      doi          = {10.5194/acp-19-425-2019},
      url          = {https://juser.fz-juelich.de/record/862051},
}