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@ARTICLE{Dlugi:866649,
      author       = {Dlugi, Ralph and Berger, Martina and Mallik, Chinmay and
                      Tsokankunku, Anywhere and Zelger, Michael and Acevedo,
                      Otávio C. and Bourtsoukidis, Efstratios and Hofzumahaus,
                      Andreas and Kesselmeier, Jürgen and Kramm, Gerhard and
                      Marno, Daniel and Martinez, Monica and Nölscher, Anke C.
                      and Ouwersloot, Huug and Pfannerstill, Eva Y. and Rohrer,
                      Franz and Tauer, Sebastian and Williams, Jonathan and
                      Yáñez-Serrano, Ana-Maria and Andreae, Meinrat O. and
                      Harder, Hartwig and Sörgel, Matthias},
      title        = {{S}egregation in the {A}tmospheric {B}oundary {L}ayer:
                      {T}he {C}ase of {OH} $\–$ {I}soprene},
      journal      = {Atmospheric chemistry and physics / Discussions Discussions
                      [...]},
      volume       = {1325},
      issn         = {1680-7375},
      address      = {Katlenburg-Lindau},
      publisher    = {EGU},
      reportid     = {FZJ-2019-05728},
      pages        = {1 - 61},
      year         = {2019},
      abstract     = {In the atmospheric boundary layer (ABL), incomplete mixing
                      (i.e., segregation) results in reduced chemical reaction
                      rates compared to those expected from mean values and rate
                      constants derived under well mixed conditions. Recently,
                      segregation has been suggested as a potential cause of
                      discrepancies between modelled and measured OH radical
                      concentrations, especially under high isoprene conditions.
                      Therefore, the influence of segregation on the reaction of
                      OH radicals with isoprene has been investigated by modelling
                      studies and one ground-based and one aircraft campaign.In
                      this study, we measured isoprene and OH radicals with high
                      time resolution in order to directly calculate the influence
                      of segregation in a low-NOx and high-isoprene environment in
                      the central Amazon basin. The calculated intensities of
                      segregation (Is) at the Amazon Tall Tower Observatory (ATTO)
                      above canopy top are in the range of values determined at a
                      temperate deciduous forest (ECHO-campaign) in a high-NOx
                      low-isoprene environment, but stay below $10 \%.$ To
                      establish a more general idea about the causes of
                      segregation and their potential limits, further analysis was
                      based on the budget equations of isoprene mixing ratios, the
                      variance of mixing ratios, and the balance of the intensity
                      of segregation itself. Furthermore, it was investigated if a
                      relation of Is to the turbulent isoprene surface flux can be
                      established theoretically and empirically, as proposed
                      previously. A direct relation is not given and the amount of
                      variance in Is explained by the isoprene flux will be higher
                      the less the influence from other processes (e.g., vertical
                      advection) is and will therefore be greater near the
                      surface. Although ground based values of Is from ATTO and
                      ECHO are in the same range, we could identify different
                      dominating processes driving Is. For ECHO the normalized
                      variance of isoprene had the largest contribution, whereas
                      for ATTO the different transport terms expressed as a
                      residual were dominating. To get a more general picture of
                      Is and its potential limits in the ABL, we also compared
                      these ground based measurements to ABL modelling studies and
                      results from an aircraft campaign. The ground based
                      measurements show the lowest values of the degree of
                      inhomogenous mixing $(< 20 \%,$ mostly below $10 \%).$
                      These values increase if the contribution of lower
                      frequencies is added. Values integrated over the whole
                      boundary layer (modelling studies) are in the range from
                      $10 \%$ to $30 \%$ and aircraft measurements integrating
                      over different landscapes are amongst the largest reported.
                      This presents evidence that larger scale heterogeneities in
                      land surface properties contribute substantially to Is.},
      cin          = {IEK-8},
      ddc          = {550},
      cid          = {I:(DE-Juel1)IEK-8-20101013},
      pnm          = {243 - Tropospheric trace substances and their
                      transformation processes (POF3-243)},
      pid          = {G:(DE-HGF)POF3-243},
      typ          = {PUB:(DE-HGF)16},
      doi          = {10.5194/acp-2018-1325},
      url          = {https://juser.fz-juelich.de/record/866649},
}