Atmospheric Chemistry and Physics Discussions
www.atmos-chem-phys-discuss.net
1680-7367
1680-7375
5
1
2005
10.5194/acpd-5-875-2005
http://www.atmos-chem-phys-discuss.net/5/875/2005/
http://www.atmos-chem-phys-discuss.net/5/875/2005/acpd-5-875-2005.html
http://www.atmos-chem-phys-discuss.net/5/875/2005/acpd-5-875-2005.pdf
875
909
2005-02-17
Midlatitude ClO during the maximum atmospheric chlorine burden: in situ balloon measurements and model simulations
B. Vogel
R. Müller
A. Engel
J.-U. Grooß
D. Toohey
T. Woyke
F. Stroh
Research Center Jülich, Institute for Stratospheric Research (ICG-I), Jülich, Germany
University of Frankfurt, Institute for Meteorology, Frankfurt, Germany
University of Colorado, Boulder, CO, USA
Etas GmbH, Stuttgart, Germany
Chlorine monoxide (ClO) plays a key role in stratospheric ozone loss
processes at midlatitudes. We present two balloonborne in situ
measurements of ClO conducted in northern hemisphere midlatitudes
during the period of the maximum of total inorganic chlorine loading
in the atmosphere. Both ClO measurements were conducted on board the
TRIPLE balloon payload, launched in November 1996 in León, Spain, and
in May 1999 in Aire sur l'Adour, France. For both flights a ClO daylight and
night time vertical profile could be derived over an altitude range of
approximately 15–31 km. ClO mixing ratios are compared to
model simulations performed with the photochemical box model version
of the Chemical Lagrangian Model of the Stratosphere
(CLaMS). Simulations along 24-h backward trajectories were
performed to study the diurnal variation of ClO in the midlatitude
lower stratosphere. Model simulations for the flight launched in
Aire sur l'Adour 1999 show a good agreement with the ClO measurements. For the
flight launched in León 1996, a similar good agreement is found,
except at around ≈650 K potential temperature (≈26 km
altitude). However, a tendency is found that for solar zenith
angles greater than 86°–87° the simulated ClO
mixing ratios substantially overestimate measured ClO by
approximately a factor of 2.5 or more for both flights. Therefore we
conclude that no indication can be deduced from the presented ClO
measurements that substantial uncertainties exist in midlatitude
chlorine chemistry of the stratosphere. An exception is the situation
at solar zenith angles greater than 86°–87° where
model simulations substantial overestimate ClO observations.
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