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| Titel |
Airborne measurements of new particle formation in the free troposphere above the Mediterranean Sea during the HYMEX campaign |
| VerfasserIn |
C. Rose, K. Sellegri, E. Freney, R. Dupuy, A. Colomb, J.-M. Pichon, M. Ribeiro, T. Bourianne, F. Burnet, A. Schwarzenboeck |
| 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. 17 ; Nr. 15, no. 17 (2015-09-14), S.10203-10218 |
| Datensatznummer |
250120031
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| Publikation (Nr.) |
 copernicus.org/acp-15-10203-2015.pdf |
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| Zusammenfassung |
| While atmospheric new particle formation (NPF) has been observed in various
environments and was found to contribute significantly to the total aerosol
particle concentration, the production of new particles over open seas is
poorly documented in the literature. Nucleation events were detected and
analysed over the Mediterranean Sea using two condensation particle counters
and a scanning mobility particle sizer on board the ATR-42 research aircraft
during flights conducted between 11 September and 4 November 2012 in the
framework of the HYMEX (HYdrological cycle in Mediterranean EXperiment)
project. The main purpose of the present work was to characterize the spatial
extent of the NPF process, both horizontally and vertically. Our findings
show that nucleation is occurring over large areas above the Mediterranean
Sea in all air mass types. Maximum concentrations of particles in the size
range 5–10 nm (N5–10) do not systematically coincide with
lower fetches (time spent by the air mass over the sea before sampling), and
significant N5–10 values are found for fetches between 0 and
60 h depending on the air mass type. These observations suggest that
nucleation events could be more influenced by local precursors originating
from emission processes occurring above the sea, rather than linked to
synoptic history. Vertical soundings were performed, giving the opportunity
to examine profiles of the N5–10 concentration and to analyse
the vertical extent of NPF. Our observations demonstrate that the process
could be favoured above 1000 m, i.e. frequently in the free troposphere, and
more especially between 2000 and 3000 m, where the NPF frequency is close to
50 %. This vertical distribution of NPF might be favoured by the
gradients of several atmospheric parameters, together with the mixing of two
air parcels, which could also explain the occurrence of the process at
preferential altitudes. In addition, increased condensation sinks collocated
with high concentrations of small particles suggest the occurrence of NPF
events promoted by inputs from the boundary layer, most probably associated
with convective clouds and their outflow. After their formation, particles
slowly grow at higher altitudes to diameters of at least 30 nm while not
being greatly depleted or affected by coagulation. Our analysis of the
particle size distributions suggests that particle growth could decrease with
increasing altitude. |
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