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| Titel |
Vertical distribution of CCN properties in the Caribbean during SALTRACE |
| VerfasserIn |
Maximilian Dollner, Bernadett Weinzierl, Adrian Walser, Thomas Kristensen, Silke Groß, Fernando Chouza, Volker Freudenthaler, Andreas Schäfler, Daniel Sauer, Melanie Kujukovic |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250112822
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| Publikation (Nr.) |
 EGU/EGU2015-13001.pdf |
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| Zusammenfassung |
| Mineral dust is an important component of the atmosphere and the climate system since
mineral dust acts as cloud condensation nuclei (CCN) as well as ice nuclei (IN) and
contributes significantly to the global annual particle emissions by mass. Every year, huge
amounts of Saharan mineral dust is transported westward across the Atlantic Ocean into
the Caribbean. During transport, the chemical and microphysical properties of the
mineral dust may be modified thereby changing the CCN properties of the dust
aerosol.
During the Saharan Aerosol Long-range Transport and Aerosol-Cloud-Interaction
Experiment (SALTRACE: http://www.pa.op.dlr.de/saltrace) in June/July 2013, CCN
measurements were performed on the DLR Falcon research aircraft with a dual
column Cloud Condensation Nuclei Counter (CCNC) first at Cape Verde then at the
Caribbean. The CCNC provides information about concentration of CCN at two
different supersaturations at the same time. For SALTRACE, one column of the
CCNC was set to 0.2% supersaturation, whereas the second column was operated in
scanning mode at different supersaturations between 0.1 and 0.5%. Additional CCN
measurements by a ground-based single column CCNC were performed at Ragged Point,
Barbados.
During SALTRACE five mineral dust outbreaks were investigated. The CCN
measurements in the Caribbean showed three layers with different CCN characteristics
during these outbreaks. In the upper part (2.5 to 4.5 km) of the Saharan Air Layer (SAL) in
the Caribbean the aerosol properties are similar to the ones measured in the dust layer over
Cape Verde and the CCNC measurements show low CCN concentrations and little activated
fraction. In contrast, a higher variability was detected in the lower part (0.7 to 2.5 km) of the
SAL. Within this layer a much higher CCN activation leads to a larger CCN concentration
and cumulus clouds were frequently observed. Below 0.7 km also a high variability in
activated fraction was observed, but CCN concentration was lower than in the lower part of
the SAL.
We will present results of the airborne CCN measurements including the vertical
distribution of CCN properties. Beyond that we assess CCN properties observed in
the Caribbean and discuss potential causes for the observed three layer structure. |
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