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@ARTICLE{Zou:893995,
      author       = {Zou, Ling and Hoffmann, Lars and Griessbach, Sabine and
                      Spang, Reinhold and Wang, Lunche},
      title        = {{E}mpirical evidence for deep convection being a major
                      source of stratospheric ice clouds over {N}orth {A}merica},
      journal      = {Atmospheric chemistry and physics},
      volume       = {21},
      number       = {13},
      issn         = {1680-7324},
      address      = {Katlenburg-Lindau},
      publisher    = {EGU},
      reportid     = {FZJ-2021-02972},
      pages        = {10457 - 10475},
      year         = {2021},
      abstract     = {Ice clouds in the lowermost stratosphere affect
                      stratospheric water vapour and the Earth's radiation budget.
                      The knowledge of its occurrence and driving forces is
                      limited. To assess the distribution and possible formation
                      mechanisms of stratospheric ice clouds (SICs) over North
                      America, we analysed SIC occurrence frequencies observed by
                      the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite
                      Observations (CALIPSO) instrument during the years 2006 to
                      2018. Possible driving forces such as deep convection are
                      assessed based on Atmospheric Infrared Sounder (AIRS)
                      observations during the same time. Results show that at
                      nighttime, SICs are most frequently observed during the
                      thunderstorm season over the Great Plains from May to August
                      (MJJA) with a maximum occurrence frequency of $6.2 \%.$
                      During the months from November to February (NDJF), the
                      highest SICs occurrence frequencies are $5.5 \%$ over the
                      north-eastern Pacific and western Canada and $4.4 \%$ over
                      the western North Atlantic. Occurrence frequencies of deep
                      convection from AIRS, which includes storm systems, fronts,
                      mesoscale convective systems, and mesoscale convective
                      complexes at midlatitude and high latitude, show similar
                      hotspots like the SICs, with highest occurrence frequencies
                      being observed over the Great Plains in MJJA $(4.4 \%)$
                      and over the north-eastern Pacific, western Canada, and the
                      western North Atlantic in NDJF $(∼ 2.5 \%).$ Both,
                      seasonal patterns and daily time series of SICs and deep
                      convection show a high degree of spatial and temporal
                      relation. Further analysis indicates that the maximum
                      fraction of SICs related to deep convection is $74 \%$
                      over the Great Plains in MJJA and about $50 \%$ over the
                      western North Atlantic, the north-eastern Pacific, and
                      western Canada in NDJF. We conclude that, locally and
                      regionally, deep convection is the leading factor related to
                      the occurrence of SICs over North America. In this study, we
                      also analysed the impact of gravity waves as another
                      important factor related to the occurrence of SICs, as the
                      Great Plains is a well-known hotspot for stratospheric
                      gravity waves. In the cases where SICs are not directly
                      linked to deep convection, we found that stratospheric
                      gravity wave observations correlate with SICs with as much
                      as $30 \%$ of the cases over the Great Plains in MJJA,
                      about $50 \%$ over the north-eastern Pacific and western
                      Canada, and up to $90 \%$ over eastern Canada and the
                      north-west Atlantic in NDJF. Our results provide a better
                      understanding of the physical processes and climate
                      variability related to SICs and will be of interest for
                      modellers as SIC sources such as deep convection and gravity
                      waves are small-scale processes that are difficult to
                      represent in global general circulation models.},
      cin          = {JSC / IEK-7},
      ddc          = {550},
      cid          = {I:(DE-Juel1)JSC-20090406 / I:(DE-Juel1)IEK-7-20101013},
      pnm          = {5111 - Domain-Specific Simulation Data Life Cycle Labs
                      (SDLs) and Research Groups (POF4-511) / DFG project
                      410579391 - Transportwege für Aerosol und Spurengase im
                      Asiatischen Monsun in der oberen Troposphäre und unteren
                      Stratosphäre},
      pid          = {G:(DE-HGF)POF4-5111 / G:(GEPRIS)410579391},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000672753300001},
      doi          = {10.5194/acp-21-10457-2021},
      url          = {https://juser.fz-juelich.de/record/893995},
}