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@ARTICLE{Zou:1010539,
      author       = {Zou, Ling and Hoffmann, Lars and Müller, Rolf and Spang,
                      Reinhold},
      title        = {{V}ariability and trends of the tropical tropopause derived
                      from a 1980–2021 multi-reanalysis assessment},
      journal      = {Frontiers in Earth Science},
      volume       = {11},
      issn         = {2296-6463},
      address      = {Lausanne},
      publisher    = {Frontiers Media},
      reportid     = {FZJ-2023-03113},
      pages        = {1177502},
      year         = {2023},
      abstract     = {As the tropopause plays a key role in regulating the entry
                      of air from the troposphere into the stratosphere and in
                      controlling stratosphere-troposphere exchange, variation of
                      the tropopause impacts the atmospheric dynamics, circulation
                      patterns, and the distribution of greenhouse gases in the
                      upper troposphere and lower stratosphere (UTLS). Therefore,
                      it is of particular interest to investigate the
                      climatological characteristics and trends of the tropopause.
                      Previous studies have investigated the tropopause
                      characteristics using reanalyses and multi-source
                      observations. This study extends the analysis of long-term
                      variability and trends of tropical tropopause
                      characteristics in earlier studies from 1980 up to 2021
                      using the modern ERA5 reanalysis and compares the results
                      with those of other reanalyses, including ERA-Interim,
                      MERRA-2, and NCEP1/2. Our analysis reveals a general rise
                      and cooling of the tropical tropopause between 1980 and
                      2021. The geopotential height has increased by approximately
                      0.06 ± 0.01 km/decade (at a $95\%$ confidence level), while
                      the temperature has decreased by −0.09 ± 0.03 K/decade
                      (at a $95\%$ confidence level) for both the lapse rate
                      tropopause and the cold point tropopause in ERA5. However,
                      from 2006 to 2021, ERA5 shows a warming tropical tropopause
                      (0.10 ± 0.11 K/decade) along with a slower rise in
                      tropopause height (0.05 ± 0.02 km/decade) (at a $95\%$
                      confidence level). Furthermore, our analysis demonstrates a
                      decline in the rise and cooling of the tropical tropopause
                      since the late 1990s, based on moving 20-year window trends
                      in ERA5. Similar trends are observed in other investigated
                      reanalyses. In addition, this study evaluated the
                      variability of the width of the tropical belt based on
                      tropopause height data from the reanalyses. The ERA5 data
                      show a narrowing tropical belt (−0.16 ± 0.11°/decade)
                      for the time period 1980–2021 according to the relative
                      threshold method. It reveals a tropical widening (0.05 ±
                      0.22°/decade) for the period between 1980 and 2005,
                      followed by a tropical narrowing (−0.17 ± 0.42°/decade)
                      after 2006. However, the large uncertainties pose a
                      challenge in drawing definitive conclusions on the change of
                      tropical belt width. Despite the many challenges involved in
                      deriving the characteristics and trends of the tropopause
                      from reanalysis data, this study and the open reanalysis
                      tropopause data sets provided to the community will help to
                      better inform future assessments of stratosphere-troposphere
                      exchange and studies of chemistry and dynamics of the upper
                      troposphere and lower stratosphere region.},
      cin          = {JSC / IEK-7 / CASA},
      ddc          = {550},
      cid          = {I:(DE-Juel1)JSC-20090406 / I:(DE-Juel1)IEK-7-20101013 /
                      I:(DE-Juel1)CASA-20230315},
      pnm          = {5111 - Domain-Specific Simulation $\&$ Data Life Cycle Labs
                      (SDLs) and Research Groups (POF4-511) / 2112 - Climate
                      Feedbacks (POF4-211)},
      pid          = {G:(DE-HGF)POF4-5111 / G:(DE-HGF)POF4-2112},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:001059168500001},
      doi          = {10.3389/feart.2023.1177502},
      url          = {https://juser.fz-juelich.de/record/1010539},
}