 |
| Titel |
Understanding global secondary organic aerosol amount and size-resolved condensational behavior |
| VerfasserIn |
S. D. D'Andrea, S. A. K. Häkkinen, D. M. Westervelt, C. Kuang, E. J. T. Levin, V. P. Kanawade, W. R. Leaitch, D. V. Spracklen, I. Riipinen, J. R. Pierce |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 13, no. 22 ; Nr. 13, no. 22 (2013-11-27), S.11519-11534 |
| Datensatznummer |
250085840
|
| Publikation (Nr.) |
 copernicus.org/acp-13-11519-2013.pdf |
|
|
|
|
|
| Zusammenfassung |
| Recent research has shown that secondary organic aerosols (SOA) are major
contributors to ultrafine particle growth to climatically relevant sizes,
increasing global cloud condensation nuclei (CCN) concentrations within the
continental boundary layer (BL). However, there are three recent
developments regarding the condensation of SOA that lead to uncertainties in
the contribution of SOA to particle growth and CCN concentrations: (1) while
many global models contain only biogenic sources of SOA (with annual
production rates generally 10–30 Tg yr−1), recent studies have shown
that an additional source of SOA around 100 Tg yr−1 correlated with
anthropogenic carbon monoxide (CO) emissions may be required to match
measurements. (2) Many models treat SOA solely as semi-volatile, which leads
to condensation of SOA proportional to the aerosol mass distribution;
however, recent closure studies with field measurements show nucleation mode
growth can be captured only if it is assumed that a significant fraction of
SOA condenses proportional to the Fuchs-corrected aerosol surface area. This
suggests a very low volatility of the condensing vapors. (3) Other recent
studies of particle growth show that SOA condensation deviates from
Fuchs-corrected surface-area condensation at sizes smaller than 10 nm and
that size-dependent growth rate parameterizations (GRP) are needed to match
measurements. We explore the significance of these three findings using
GEOS-Chem-TOMAS global aerosol microphysics model and observations of
aerosol size distributions around the globe. The change in the concentration
of particles of size Dp > 40 nm (N40) within the BL
assuming surface-area condensation compared to mass-distribution net
condensation yielded a global increase of 11% but exceeded 100% in
biogenically active regions. The percent change in N40 within the BL with
the inclusion of the additional 100 Tg SOA yr−1 compared to the base
simulation solely with biogenic SOA emissions (19 Tg yr−1) both using
surface area condensation yielded a global increase of 13.7%, but
exceeded 50% in regions with large CO emissions. The inclusion of two
different GRPs in the additional-SOA case both yielded a global increase in
N40 of < 1%, however exceeded 5% in some locations in the most
extreme case. All of the model simulations were compared to measured data
obtained from diverse locations around the globe and the results confirmed a
decrease in the model-measurement bias and improved slope for comparing
modeled to measured CCN number concentration when non-volatile SOA was
assumed and the extra SOA was included. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|