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| Titel |
Global distribution of sea salt aerosols: new constraints from in situ and remote sensing observations |
| VerfasserIn |
L. Jaeglé, P. K. Quinn, T. S. Bates, B. Alexander, J.-T. Lin |
| 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 ; 11, no. 7 ; Nr. 11, no. 7 (2011-04-04), S.3137-3157 |
| Datensatznummer |
250009584
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| Publikation (Nr.) |
 copernicus.org/acp-11-3137-2011.pdf |
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| Zusammenfassung |
| We combine in situ measurements of sea salt aerosols (SS) from open ocean
cruises and ground-based stations together with aerosol optical depth (AOD)
observations from MODIS and AERONET, and the GEOS-Chem global chemical
transport model to provide new constraints on SS emissions over the world's
oceans. We find that the GEOS-Chem model using the Gong (2003) source
function overestimates cruise observations of coarse mode SS mass
concentrations by factors of 2–3 at high wind speeds over the cold waters of
the Southern, North Pacific and North Atlantic Oceans. Furthermore, the
model systematically underestimates SS over the warm tropical waters of the
Central Pacific, Atlantic, and Indian Oceans. This pattern is confirmed by
SS measurements from a global network of 15 island and coastal stations. The
model discrepancy at high wind speeds (>6 m s
−1) has a clear
dependence on sea surface temperature (SST). We use the cruise observations
to derive an empirical SS source function depending on both wind speed and
SST. Implementing this new source function in GEOS-Chem results in improved
agreement with in situ observations, with a decrease in the model bias from
+64% to +33% for the cruises and from +32% to −5% for the
ground-based sites. We also show that the wind speed-SST source function
significantly improves agreement with MODIS and AERONET AOD, and provides an
explanation for the high AOD observed over the tropical oceans. With the
wind speed-SST formulation, global SS emissions show a small decrease from
5200 Mg yr−1 to 4600 Mg yr−1, while the SS burden decreases from 9.1 to 8.5 mg m−2. The spatial distribution of SS, however, is greatly affected,
with the SS burden increasing by 50% in the tropics and decreasing by
40% at mid- and high-latitudes. Our results imply a stronger than
expected halogen source from SS in the tropical marine boundary layer. They
also imply stronger radiative forcing of SS in the tropics and a larger
response of SS emissions to climate change than previously thought. |
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