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@ARTICLE{Kanaya:20323,
author = {Kanaya, Y. and Hofzumahaus, A. and Dorn, H.-P. and Brauers,
T. and Fuchs, H. and Holland, F. and Rohrer, F. and Bohn, B.
and Tillmann, R. and Wegener, R. and Wahner, A. and Kajii,
Y. and Miyamoto, K. and Nishida, S. and Watanabe, K. and
Yoshino, A. and Kubistin, D. and Martinez, M. and Rudolf, M.
and Harder, H. and Berresheim, H. and Elste, T. and
Plass-Dülmer, C. and Stange, G. and Kleffmann, J. and
Elshorbany, Y. and Schurath, U.},
title = {{C}omparisons of observed and modeled {OH} and {HO}2
concentrations during the ambient measurement period of the
{HO}x{C}omp field campaign},
journal = {Atmospheric chemistry and physics},
volume = {12},
issn = {1680-7316},
address = {Katlenburg-Lindau},
publisher = {EGU},
reportid = {PreJuSER-20323},
pages = {2567 - 2585},
year = {2012},
note = {Helpful comments by two anonymous reviewers are greatly
appreciated. This work was supported by the EU FP-6 program
EUROCHAMP (grant no. RII3-CT-2004-505968), ACCENT (Priority
1.1.6.3. Global Change and Ecosystems, grant no.
GOCE-CT-2004-505337), a Grant-in-Aid for Scientific Research
(KAKENHI) (B) 22310018 and RR2002 of the Kyosei Project by
the Ministry of Education, Science, Sports, and Culture of
Japan. We thank F. J. Johnen for assistance with the
experiments and K. D. Lu for discussions.},
abstract = {A photochemical box model constrained by ancillary
observations was used to simulate OH and HO2 concentrations
for three days of ambient observations during the HO(x)Comp
field campaign held in Julich, Germany in July 2005. Daytime
OH levels observed by four instruments were fairly well
reproduced to within $33\%$ by a base model run (Regional
Atmospheric Chemistry Mechanism with updated isoprene
chemistry adapted from Master Chemical Mechanism ver. 3.1)
with high R-2 values (0.72-0.97) over a range of isoprene
(0.3-2 ppb) and NO (0.1-10 ppb) mixing ratios. Daytime
HO2(*) levels, reconstructed from the base model results
taking into account the sensitivity toward speciated RO2
(organic peroxy) radicals, as recently reported from one of
the participating instruments in the HO2 measurement mode,
were $93\%$ higher than the observations made by the single
instrument. This also indicates an overprediction of the HO2
to OH recycling. Together with the good model-measurement
agreement for OH, it implies a missing OH source in the
model. Modeled OH and HO2(*) could only be matched to the
observations by addition of a strong unknown loss process
for HO2(*) that recycles OH at a high yield. Adding to the
base model, instead, the recently proposed isomerization
mechanism of isoprene peroxy radicals (Peeters and Muller,
2010) increased OH and HO2(*) by $28\%$ and $13\%$ on
average. Although these were still only $4\%$ higher than
the OH observations made by one of the instruments, larger
overestimations $(42-70\%)$ occurred with respect to the OH
observations made by the other three instruments. The
overestimation in OH could be diminished only when reactive
alkanes (HC8) were solely introduced to the model to explain
the missing fraction of observed OH reactivity. Moreover,
the overprediction of HO2(*) became even larger than in the
base case. These analyses imply that the rates of the
isomerization are not readily supported by the ensemble of
radical observations. One of the measurement days was
characterized by low isoprene concentrations (similar to 0.5
ppb) and OH reactivity that was well explained by the
observed species, especially before noon. For this selected
period, as opposed to the general behavior, the model tended
to underestimate HO2(*). We found that this tendency is
associated with high NOx concentrations, suggesting that
some HO2 production or regeneration processes under high NOx
conditions were being overlooked; this might require
revision of ozone production regimes.},
keywords = {J (WoSType)},
cin = {IEK-8},
ddc = {550},
cid = {I:(DE-Juel1)IEK-8-20101013},
pnm = {Atmosphäre und Klima},
pid = {G:(DE-Juel1)FUEK491},
shelfmark = {Meteorology $\&$ Atmospheric Sciences},
typ = {PUB:(DE-HGF)16},
UT = {WOS:000301547500021},
doi = {10.5194/acp-12-2567-2012},
url = {https://juser.fz-juelich.de/record/20323},
}