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| Titel |
An empirically derived inorganic sea spray source function incorporating sea surface temperature |
| VerfasserIn |
M. E. Salter, P. Zieger, J. C. Acosta Navarro, H. Grythe, A. Kirkevåg, B. Rosati, I. Riipinen, E. D. Nilsson |
| 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. 19 ; Nr. 15, no. 19 (2015-10-06), S.11047-11066 |
| Datensatznummer |
250120076
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| Publikation (Nr.) |
 copernicus.org/acp-15-11047-2015.pdf |
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| Zusammenfassung |
We have developed an inorganic sea spray source function that is based upon
state-of-the-art measurements of sea spray aerosol production using
a temperature-controlled plunging jet sea spray aerosol chamber. The
size-resolved particle production was measured between 0.01 and
10 μm dry diameter. Particle production decreased non-linearly with
increasing seawater temperature (between −1 and 30 °C) similar to
previous findings. In addition, we observed that the particle effective
radius, as well as the particle surface, particle volume and particle mass, increased with
increasing seawater temperature due to increased production of particles with
dry diameters greater than 1 μm. By combining these measurements
with the volume of air entrained by the plunging jet we have determined the
size-resolved particle flux as a function of air entrainment. Through the use
of existing parameterisations of air entrainment as a function of wind speed,
we were subsequently able to scale our laboratory measurements of particle
production to wind speed. By scaling in this way we avoid some of the
difficulties associated with defining the "white area" of the laboratory
whitecap – a contentious issue when relating laboratory measurements of
particle production to oceanic whitecaps using the more frequently applied
whitecap method.
The here-derived inorganic sea spray source function was implemented in
a Lagrangian particle dispersion model (FLEXPART – FLEXible PARTicle dispersion model). An estimated annual global
flux of inorganic sea spray aerosol of 5.9 ± 0.2 Pg yr−1 was
derived that is close to the median of estimates from the same model using
a wide range of existing sea spray source functions. When using the source
function derived here, the model also showed good skill in predicting
measurements of Na+ concentration at a number of field sites further
underlining the validity of our source function.
In a final step, the sensitivity of a large-scale model
(NorESM – the Norwegian Earth System Model) to our new
source function was tested. Compared to the previously implemented
parameterisation, a clear decrease of sea spray aerosol number flux and
increase in aerosol residence time was observed, especially over the Southern
Ocean. At the same time an increase in aerosol optical depth due to an
increase in the number of particles with optically relevant sizes was found.
That there were noticeable regional differences may have important
implications for aerosol optical properties and number concentrations,
subsequently also affecting the indirect radiative forcing by non-sea spray
anthropogenic aerosols. |
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