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| Titel |
The effect of model spatial resolution on Secondary Organic Aerosol predictions: a case study at Whistler, BC, Canada |
| VerfasserIn |
C. D. Wainwright, J. R. Pierce, J. Liggio, K. B. Strawbridge, A. M. Macdonald, R. W. Leaitch |
| 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. 22 ; Nr. 12, no. 22 (2012-11-20), S.10911-10923 |
| Datensatznummer |
250011606
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| Publikation (Nr.) |
 copernicus.org/acp-12-10911-2012.pdf |
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| Zusammenfassung |
| A large fraction of submicron aerosol mass throughout the continental
boundary layer consists of secondary organic aerosol (SOA) mass. As such,
the ability of chemical transport models to accurately predict continental
boundary layer aerosol greatly depends on their ability to predict SOA.
Although there has been much recent effort to better describe SOA formation
mechanisms in models, little attention has been paid to the effects of model
spatial resolution on SOA predictions. The Whistler Aerosol and Cloud Study
(WACS 2010), held between 22 June and 28 July 2010 and
conducted at Whistler, BC, Canada provides a unique data set for testing
simulated SOA predictions. The study consisted of intensive measurements of
atmospheric trace gases and particles at several locations strongly
influenced by biogenic sources in the region. We test the ability of the
global chemical transport model GEOS-Chem to predict the aerosol
concentrations during this event and throughout the campaign. Simulations
were performed using three different resolutions of the model:
4° × 5° , 2° × 2.5° and 0.5° × 0.667°.
Predictions of organic aerosol concentrations at Whistler were greatly
dependent on the resolution; the 4° × 5°
version of the model significantly under predicts organic aerosol, while the
2° × 2.5° and 0.5° × 0.667° versions are much more closely correlated with
measurements. In addition, we performed a comparison between the 3 versions
of the model across North America. Comparison simulations were run for both
a summer case (July) and Winter case (January). For the summer case,
0.5° × 0.667° simulations predicted on
average 19% more SOA than 2° × 2.5° and
32% more than 4° × 5° . For the winter
case, the 0.5° × 0.667° simulations predicted
8% more SOA than the 2° × 2.5° and 23%
more than the 4° × 5°. This increase in SOA
with resolution is largely due to sub-grid variability of organic aerosol
(OA) that leads to an increase in the partitioning of secondary organic
matter to the aerosol phase at higher resolutions. SOA concentrations were
further increased because the shift of secondary organic gases to SOA at
higher resolutions increased the lifetime of secondary organic matter
(secondary organic gases have a shorter deposition lifetime than SOA in the
model). SOA precursor emissions also have smaller, but non-negligible,
changes with resolution due to non-linear inputs to the MEGAN biogenic
emissions scheme. These results suggest that a portion of the traditional
under-prediction of SOA by global models may be due to the effects of coarse
grid resolution. |
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