 |
| Titel |
Weak global sensitivity of cloud condensation nuclei and the aerosol indirect effect to Criegee + SO2 chemistry |
| VerfasserIn |
J. R. Pierce, M. J. Evans, C. E. Scott, S. D. D'Andrea, D. K. Farmer, E. Swietlicki, D. V. Spracklen |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 13, no. 6 ; Nr. 13, no. 6 (2013-03-15), S.3163-3176 |
| Datensatznummer |
250018525
|
| Publikation (Nr.) |
 copernicus.org/acp-13-3163-2013.pdf |
|
|
|
|
|
| Zusammenfassung |
| H2SO4 vapor is important for the nucleation of atmospheric
aerosols and the growth of ultrafine particles to cloud condensation nuclei
(CCN) sizes with important roles in the global aerosol budget and hence
planetary radiative forcing. Recent studies have found that reactions of
stabilized Criegee intermediates (CIs, formed from the ozonolysis of
alkenes) with SO2 may be an important source of H2SO4 that
has been missing from atmospheric aerosol models. For the first time in a
global model, we investigate the impact of this new source of
H2SO4 in the atmosphere. We use the chemical transport model,
GEOS-Chem, with the online aerosol microphysics module, TOMAS, to estimate
the possible impact of CIs on present-day H2SO4, CCN, and the
cloud-albedo aerosol indirect effect (AIE). We extend the standard GEOS-Chem
chemistry with CI-forming reactions (ozonolysis of isoprene, methyl vinyl
ketone, methacrolein, propene, and monoterpenes) from the Master Chemical
Mechanism. Using a fast rate constant for CI+SO2, we find that the
addition of this chemistry increases the global production of
H2SO4 by 4%. H2SO4 concentrations increase by over
100% in forested tropical boundary layers and by over 10–25% in
forested NH boundary layers (up to 100% in July) due to CI+SO2
chemistry, but the change is generally negligible elsewhere. The predicted
changes in CCN were strongly dampened to the CI+SO2 changes in
H2SO4 in some regions: less than 15% in tropical forests and
less than 2% in most mid-latitude locations. The global-mean CCN change
was less than 1% both in the boundary layer and the free troposphere. The
associated cloud-albedo AIE change was less than 0.03 W m−2. The model
global sensitivity of CCN and the AIE to CI+SO2 chemistry is
significantly (approximately one order-of-magnitude) smaller than the
sensitivity of CCN and AIE to other uncertain model inputs, such as
nucleation mechanisms, primary emissions, SOA (secondary organic aerosol) and deposition. Similarly,
comparisons to size-distribution measurements show that uncertainties in
other model parameters dominate model biases in the model-predicted size
distributions. We conclude that improvement in the modeled CI+SO2
chemistry would not likely lead to significant improvements in
present-day CCN and AIE predictions. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|