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@ARTICLE{Braun:862202,
author = {Braun, Marleen and Grooß, Jens-Uwe and Woiwode, Wolfgang
and Johansson, Sören and Höpfner, Michael and
Friedl-Vallon, Felix and Oelhaf, Hermann and Preusse, Peter
and Ungermann, Jörn and Sinnhuber, Björn-Martin and
Ziereis, Helmut and Braesicke, Peter},
title = {{N}itrification of the lowermost stratosphere during the
exceptionally cold {A}rctic winter 2015/16},
journal = {Atmospheric chemistry and physics / Discussions Discussions
[...]},
volume = {108},
issn = {1680-7375},
address = {Katlenburg-Lindau},
publisher = {EGU},
reportid = {FZJ-2019-02550},
pages = {1 - 25},
year = {2019},
abstract = {The Arctic winter 2015/16 was characterized by
exceptionally cold stratospheric temperatures, favouring the
formation of polar stratospheric clouds (PSCs) from
mid-December until the end of February down to low
stratospheric altitudes. Observations by GLORIA (Gimballed
Limb Observer for Radiance Imaging of the Atmosphere) on
HALO (High Altitude and LOng range research aircraft) during
the PGS (POLSTRACC/GW-LCYLCE II/SALSA) campaign from
December 2015 to March 2016 allow an investigation of the
influence of denitrification on the lowermost stratosphere
(LMS) with a high spatial resolution. For the first time
vertical cross-sections of nitric acid (HNO3) along the
flight track and tracer-tracer correlations derived from the
GLORIA observations document detailed pictures of
wide-spread nitrification of the Arctic LMS during the
course of an entire winter. GLORIA observations show
large-scale structures and local fine structures with
strongly enhanced absolute HNO3 volume mixing ratios
reaching up to 11 ppbv at altitudes of 11 km in January
and nitrified filaments persisting until the middle of
March. Narrow streaks of enhanced HNO3, observed in
mid-January, are interpreted as regions recently nitrified
by sublimating HNO3-containing particles. Overall, a
nitrification of the LMS between 5.0 ppbv and 7.0 ppbv
at potential temperature levels between 350 and 380 K is
estimated. This extent of nitrification has never been
observed before in the Arctic lowermost stratosphere. The
GLORIA observations are compared with CLaMS (Chemical
Lagrangian Model of the Stratosphere) simulations. The
fundamental structures observed by GLORIA are well
reproduced, but differences in the fine structures are
diagnosed. Further, CLaMS predominantly underestimates the
spatial extent of maximum HNO3 mixing ratios derived from
the GLORIA observations as well as the enhancement at lower
altitudes. Sensitivity simulations with CLaMS including (i)
enhanced sedimentation rates in case of ice supersaturation
(to resemble ice nucleation on NAT), (ii) a global
temperature offset, (iii) modified growth rates (to resemble
aspherical particles with larger surfaces) and (iv)
temperature fluctuations (to resemble the impact of
small-scale mountain waves) mostly improve the agreement
with the GLORIA observations. The sensitivity simulations
suggest that details of particle microphysics play a
significant role for simulated LMS nitrification in January,
while air subsidence, transport and mixing become
increasingly important towards the end of the winter.},
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},
doi = {10.5194/acp-2019-108},
url = {https://juser.fz-juelich.de/record/862202},
}