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| Titel |
Evaluation of HOx sources and cycling using measurement-constrained model calculations in a 2-methyl-3-butene-2-ol (MBO) and monoterpene (MT) dominated ecosystem |
| VerfasserIn |
S. Kim, G. M. Wolfe, L. Mauldin, C. Cantrell, A. Guenther, T. Karl, A. Turnipseed, J. Greenberg, S. R. Hall, K. Ullmann, E. Apel, R. Hornbrook, Y. Kajii, Y. Nakashima, F. N. Keutsch, J. P. DiGangi, S. B. Henry, L. Kaser, R. Schnitzhofer, M. Graus, A. Hansel, W. Zheng, F. F. Flocke |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 13, no. 4 ; Nr. 13, no. 4 (2013-02-21), S.2031-2044 |
| Datensatznummer |
250018423
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| Publikation (Nr.) |
 copernicus.org/acp-13-2031-2013.pdf |
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| Zusammenfassung |
| We present a detailed analysis of OH observations from the BEACHON
(Bio-hydro-atmosphere interactions of Energy, Aerosols, Carbon, H2O,
Organics and Nitrogen)-ROCS (Rocky Mountain Organic Carbon Study) 2010 field
campaign at the Manitou Forest Observatory (MFO), which is a
2-methyl-3-butene-2-ol (MBO) and monoterpene (MT) dominated forest
environment. A comprehensive suite of measurements was used to constrain
primary production of OH via ozone photolysis, OH recycling from HO2, and
OH chemical loss rates, in order to estimate the steady-state concentration
of OH. In addition, the University of Washington Chemical Model (UWCM) was
used to evaluate the performance of a near-explicit chemical mechanism. The
diurnal cycle in OH from the steady-state calculations is in good agreement
with measurement. A comparison between the photolytic production rates and
the recycling rates from the HO2 + NO reaction shows that recycling
rates are ~20 times faster than the photolytic OH production rates from
ozone. Thus, we find that direct measurement of the recycling rates and the
OH loss rates can provide accurate predictions of OH concentrations. More
importantly, we also conclude that a conventional OH recycling pathway
(HO2 + NO) can explain the observed OH levels in this non-isoprene
environment. This is in contrast to observations in isoprene-dominated
regions, where investigators have observed significant underestimation of OH
and have speculated that unknown sources of OH are responsible. The
highly-constrained UWCM calculation under-predicts observed HO2 by as much
as a factor of 8. As HO2 maintains oxidation capacity by recycling to OH,
UWCM underestimates observed OH by as much as a factor of 4. When the UWCM
calculation is constrained by measured HO2, model calculated OH is in
better agreement with the observed OH levels. Conversely, constraining the
model to observed OH only slightly reduces the model-measurement HO2
discrepancy, implying unknown HO2 sources. These findings demonstrate the
importance of constraining the inputs to, and recycling within, the
ROx radical pool (OH + HO2 + RO2). |
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