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| Titel |
Gas and aerosol carbon in California: comparison of measurements and model predictions in Pasadena and Bakersfield |
| VerfasserIn |
K. R. Baker, A. G. Carlton, T. E. Kleindienst, J. H. Offenberg, M. R. Beaver, D. R. Gentner, A. H. Goldstein, P. L. Hayes, J. L. Jimenez, J. B. Gilman, J. A. Gouw, M. C. Woody, H. O. T. Pye, J. T. Kelly, M. Lewandowski, M. Jaoui, P. S. Stevens, W. H. Brune, Y.-H. Lin, C. L. Rubitschun, J. D. Surratt |
| 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 ; 15, no. 9 ; Nr. 15, no. 9 (2015-05-12), S.5243-5258 |
| Datensatznummer |
250119706
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| Publikation (Nr.) |
 copernicus.org/acp-15-5243-2015.pdf |
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| Zusammenfassung |
Co-located measurements of fine particulate matter (PM2.5) organic
carbon (OC), elemental carbon, radiocarbon (14C), speciated volatile
organic compounds (VOCs), and OH radicals during the CalNex field campaign
provide a unique opportunity to evaluate the Community Multiscale Air Quality
(CMAQ) model's representation of organic species from VOCs to particles.
Episode average daily 23 h
average 14C analysis indicates PM2.5 carbon at Pasadena and
Bakersfield during the CalNex field campaign was evenly split between
contemporary and fossil origins. CMAQ predicts a higher contemporary carbon
fraction than indicated by the 14C analysis at both locations. The model
underestimates measured PM2.5 organic carbon at both sites with very
little (7% in Pasadena) of the modeled mass represented by secondary
production, which contrasts with the ambient-based SOC / OC fraction of
63% at Pasadena.
Measurements and predictions of gas-phase anthropogenic species, such as
toluene and xylenes, are generally within a factor of 2, but the
corresponding SOC tracer
(2,3-dihydroxy-4-oxo-pentanoic acid) is systematically underpredicted by
more than a factor of 2. Monoterpene VOCs and SOCs are underestimated at
both sites. Isoprene is underestimated at Pasadena and overpredicted at
Bakersfield and isoprene SOC mass is underestimated at both sites.
Systematic model underestimates in SOC mass coupled with reasonable skill
(typically within a factor of 2) in predicting hydroxyl radical and VOC gas-phase precursors suggest error(s) in the parameterization of semivolatile
gases to form SOC. Yield values (α) applied to semivolatile
partitioning species were increased by a factor of 4 in CMAQ for a
sensitivity simulation, taking into account recent findings of underestimated
yields in chamber experiments due to gas wall losses. This sensitivity
resulted in improved model performance for PM2.5 organic carbon at both
field study locations and at routine monitor network sites in California.
Modeled percent secondary contribution (22% at Pasadena) becomes closer
to ambient-based estimates but still contains a higher primary fraction than
observed. |
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