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@ARTICLE{Weigel:901817,
      author       = {Weigel, Ralf and Mahnke, Christoph and Baumgartner, Manuel
                      and Krämer, Martina and Spichtinger, Peter and Spelten,
                      Nicole and Afchine, Armin and Rolf, Christian and Viciani,
                      Silvia and D'Amato, Francesco and Tost, Holger and Borrmann,
                      Stephan},
      title        = {{I}n situ observation of new particle formation ({NPF}) in
                      the tropical tropopause layer of the 2017 {A}sian monsoon
                      anticyclone – {P}art 2: {NPF} inside ice clouds},
      journal      = {Atmospheric chemistry and physics},
      volume       = {21},
      number       = {17},
      issn         = {1680-7324},
      address      = {Katlenburg-Lindau},
      publisher    = {EGU},
      reportid     = {FZJ-2021-03841},
      pages        = {13455 - 13481},
      year         = {2021},
      abstract     = {From 27 July to 10 August 2017, the airborne StratoClim
                      mission took place in Kathmandu, Nepal, where eight mission
                      flights were conducted with the M-55 Geophysica up to
                      altitudes of 20 km. New particle formation (NPF) was
                      identified by the abundant presence of nucleation-mode
                      aerosols, with particle diameters dp smaller than 15 nm,
                      which were in-situ-detected by means of condensation nuclei
                      (CN) counter techniques. NPF fields in clear skies as well
                      as in the presence of cloud ice particles (dp > 3 µm)
                      were encountered at upper troposphere–lowermost
                      stratosphere (UTLS) levels and within the Asian monsoon
                      anticyclone (AMA). NPF-generated nucleation-mode particles
                      in elevated concentrations (Nnm) were frequently found
                      together with cloud ice (in number concentrations Nice of up
                      to 3 cm−3) at heights between ∼ 11 and 16 km. From
                      a total measurement time of ∼ 22.5 h above 10 km
                      altitude, in-cloud NPF was in sum detected over
                      ∼ 1.3 h $(∼ 50 \%$ of all NPF records throughout
                      StratoClim). Maximum Nnm of up to ∼ 11 000 cm−3
                      was detected coincidently with intermediate ice particle
                      concentrations Nice of 0.05–0.1 cm−3 at comparatively
                      moderate carbon monoxide (CO) contents of
                      ∼ 90–100 nmol mol−1. Neither under clear-sky nor
                      during in-cloud NPF do the highest Nnm concentrations
                      correlate with the highest CO mixing ratios, suggesting that
                      an elevated pollutant load is not a prerequisite for NPF.
                      Under clear-air conditions, NPF with elevated Nnm
                      (> 8000 cm−3) occurred slightly less often than within
                      clouds. In the presence of cloud ice, NPF with Nnm between
                      1500–4000 cm−3 was observed about twice as often as
                      under clear-air conditions. NPF was not found when ice water
                      contents exceeded 1000 µmol mol−1 in very cold air
                      (< 195 K) at tropopause levels. This indicates a
                      reduction in NPF once deep convection is prevalent together
                      with the presence of mainly liquid-origin ice particles.
                      Within in situ cirrus near the cold point tropopause, recent
                      NPF or intense events with mixing ration nnm larger than
                      5000 mg−1 were observed only in about $6 \%$ of the
                      in-cloud NPF data. In determining whether the cloud-internal
                      NPF is attenuated or prevented by the microphysical
                      properties of cloud elements, the integral radius (IR) of
                      the ice cloud population turned out to be indicative.
                      Neither the number of ice particles nor the free distance
                      between the ice particles is clearly related to the NPF rate
                      detected. While the increase in ice particles' mass per time
                      (dmdt) is proportional to the IR and mainly due to the
                      condensation of water vapour, additional condensation of NPF
                      precursors proceeds at the expense of the NPF rate as the
                      precursor's saturation ratio declines. Numerical simulations
                      show the impact of the IR on the supersaturation of a
                      condensable vapour, such as sulfuric acid, and furthermore
                      illustrate that the IR of the cloud ice determines the
                      effective limitation of NPF rates.},
      cin          = {IEK-7},
      ddc          = {550},
      cid          = {I:(DE-Juel1)IEK-7-20101013},
      pnm          = {2112 - Climate Feedbacks (POF4-211)},
      pid          = {G:(DE-HGF)POF4-2112},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000695647300002},
      doi          = {10.5194/acp-21-13455-2021},
      url          = {https://juser.fz-juelich.de/record/901817},
}