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@ARTICLE{Berresheim:29243,
author = {Berresheim, H. and Plass-Dülmer, C. and Elste, T. and
Mihalopoulos, N. and Rohrer, F.},
title = {{OH} in the coastal boundary layer of {C}rete during
{MINOS} : measurements and relationship with ozone
photolysis},
journal = {Atmospheric chemistry and physics},
volume = {3},
issn = {1680-7316},
address = {Katlenburg-Lindau},
publisher = {EGU},
reportid = {PreJuSER-29243},
pages = {639 - 649},
year = {2003},
note = {Record converted from VDB: 12.11.2012},
abstract = {Hydroxyl radical (OH) concentrations were measured in
August 2001 at Finokalia Station on the northeastern coast
of Crete during the Mediterranean Intensive Oxidant Study
(MINOS). OH was measured based on selected ion chemical
ionization mass spectrometry (SI/CIMS) with a time
resolution of 30 sec and signal integration of 5 min. The
corresponding accuracy, precision, and detection limit were
$20\%$ (1sigma), $11\%$ (1sigma), and 2.4 x 10(5) molecules
cm(-3) (2sigma), respectively. OH levels showed a strong
diurnal variability with high maxima (approximately 2 x
10(7) molecules cm(-3)) occurring around 13:30 LT (10:30
UTC) and nighttime values below the detection limit. Daily
24-hour average concentrations varied between 3.6-6.7 x
10(6) cm(-3). For the total measurement period (6-21 August)
the mean and standard deviation were 4.5 +/- 1.1 x 10(6)
cm(-3). The OH data set is analyzed based on a
classification into three periods: I: Aug 6-8, II: Aug 9-11,
III: Aug 13-18. For each of the three periods the measured
OH concentrations are described by the empirical function
[OH] = a J((OD)-D-1)(b), with J((OD)-D-1) being the ozone
photolysis frequency and a = 1.4 x 10(10) s cm(-3), 1.7 x
10(10) s cm(-3), 2.2 x 10(10) s cm(-3), and b = 0.68,
respectively. Taking into account the estimated precision of
the OH measurements this empirical function using three
values for a and one value for b explains $99\%$ of the
observed variance of OH. A detailed sensitivity analysis
using a CH4-CO box model was performed to interpret this
relationship, in particular the meanings of the
pre-exponential factor a and the exponent b. It was found
that the value of b which represents the total logarithmic
dependence of [OH] on J((OD)-D-1) includes the individual
contributions from the photolysis of O-3, NO2, HCHO, HONO,
and H2O2 which could be determined using the box model. For
the conditions prevailing during the MINOS campaign the
exponent b was found to be dominated by the contributions
from O-3- and NO2-photolysis. For the in-dividual functional
dependences between [OH] and J((OD)-D-1), [OH] and J(NO2),
and J(NO2) and J((OD)-D-1) the partial logarithmic
derivatives were determined to be 0.5, 0.6, and 0.3,
respectively. Overall, the box model yields a value of 0.70
for the exponent b in very good agreement with the
corresponding value derived from the empirical analysis of
the measurements. This empirical approach in which the
chemical air mass characteristics influencing the OH radical
balance and thereby, the self-cleansing efficiency of the
atmosphere, are represented by only two parameters which are
constant over quite substantial time periods may be used in
future experiments to test and compare OH measurements made
in different atmospheric environments.},
keywords = {J (WoSType)},
cin = {ICG-II},
ddc = {550},
cid = {I:(DE-Juel1)VDB48},
pnm = {Chemie und Dynamik der Geo-Biosphäre},
pid = {G:(DE-Juel1)FUEK257},
shelfmark = {Meteorology $\&$ Atmospheric Sciences},
typ = {PUB:(DE-HGF)16},
UT = {WOS:000183456700004},
doi = {10.5194/acp-3-639-2003},
url = {https://juser.fz-juelich.de/record/29243},
}