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| Titel |
In-canopy gas-phase chemistry during CABINEX 2009: sensitivity of a 1-D canopy model to vertical mixing and isoprene chemistry |
| VerfasserIn |
A. M. Bryan, S. B. Bertman, M. A. Carroll, S. Dusanter, G. D. Edwards, R. Forkel, S. Griffith, A. B. Guenther, R. F. Hansen, D. Helmig, B. T. Jobson, F. N. Keutsch, B. L. Lefer, S. N. Pressley, P. B. Shepson, P. S. Stevens, A. L. Steiner |
| 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 ; 12, no. 18 ; Nr. 12, no. 18 (2012-09-28), S.8829-8849 |
| Datensatznummer |
250011481
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| Publikation (Nr.) |
 copernicus.org/acp-12-8829-2012.pdf |
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| Zusammenfassung |
| Vegetation emits large quantities of biogenic volatile organic compounds
(BVOC). At remote sites, these compounds are the dominant precursors to ozone
and secondary organic aerosol (SOA) production, yet current field studies
show that atmospheric models have difficulty in capturing the observed
HOx cycle and concentrations of BVOC oxidation products. In this
manuscript, we simulate BVOC chemistry within a forest canopy using a
one-dimensional canopy-chemistry model (Canopy Atmospheric CHemistry Emission
model; CACHE) for a mixed deciduous forest in northern Michigan during the
CABINEX 2009 campaign. We find that the base-case model, using
fully-parameterized mixing and the simplified biogenic chemistry of the
Regional Atmospheric Chemistry Model (RACM), underestimates daytime in-canopy
vertical mixing by 50–70% and by an order of magnitude at night, leading
to discrepancies in the diurnal evolution of HOx, BVOC, and BVOC
oxidation products. Implementing observed micrometeorological data from above
and within the canopy substantially improves the diurnal cycle of modeled
BVOC, particularly at the end of the day, and also improves the
observation-model agreement for some BVOC oxidation products and OH
reactivity. We compare the RACM mechanism to a version that includes the
Mainz isoprene mechanism (RACM-MIM) to test the model sensitivity to enhanced
isoprene degradation. RACM-MIM simulates higher concentrations of both
primary BVOC (isoprene and monoterpenes) and oxidation products (HCHO,
MACR+MVK) compared with RACM simulations. Additionally, the revised mechanism
alters the OH concentrations and increases HO2. These changes generally
improve agreement with HOx observations yet overestimate BVOC
oxidation products, indicating that this isoprene mechanism does not improve
the representation of local chemistry at the site. Overall, the revised
mechanism yields smaller changes in BVOC and BVOC oxidation product
concentrations and gradients than improving the parameterization of vertical
mixing with observations, suggesting that uncertainties in vertical mixing
parameterizations are an important component in understanding observed BVOC
chemistry. |
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