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| Titel |
Physical properties of the sub-micrometer aerosol over the Amazon rain forest during the wet-to-dry season transition - comparison of modeled and measured CCN concentrations |
| VerfasserIn |
J. Rissler, E. Swietlicki, J. Zhou, G. Roberts, M. O. Andreae, L. V. Gatti, P. Artaxo |
| 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 ; 4, no. 8 ; Nr. 4, no. 8 (2004-11-02), S.2119-2143 |
| Datensatznummer |
250002065
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| Publikation (Nr.) |
 copernicus.org/acp-4-2119-2004.pdf |
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| Zusammenfassung |
| Sub-micrometer atmospheric aerosol particles were studied in the Amazon
region, 125 km northeast of Manaus, Brazil (-1°55.2'S, 59°28.1'W).
The measurements were performed during the wet-to-dry transition period,
4-28 July 2001 as part of the LBA (Large-Scale Biosphere Atmosphere
Experiment in Amazonia) CLAIRE-2001 (Cooperative LBA Airborne Regional
Experiment) experiment. The number size distribution was measured with two
parallel differential mobility analyzers, the hygroscopic growth at 90%
RH with a Hygroscopic Tandem Mobility Analyzer (H-TDMA) and the
concentrations of cloud condensation nuclei (CCN) with a cloud condensation
nuclei counter. A model was developed that uses the H-TDMA data to predict
the number of soluble molecules or ions in the individual particles and the
corresponding minimum particle diameter for activation into a cloud droplet
at a certain supersaturation. Integrating the number size distribution above
this diameter, CCN concentrations were predicted with a time resolution of
10 min and compared to the measured concentrations. During the study period,
three different air masses were identified and compared: clean background,
air influenced by aged biomass burning, and moderately polluted air from
recent local biomass burning. For the clean period 2001, similar number size
distributions and hygroscopic behavior were observed as during the wet
season at the same site in 1998, with mostly internally mixed particles of
low diameter growth factor (~1.3 taken from dry to 90% RH). During
the periods influenced by biomass burning the hygroscopic growth changed
slightly, but the largest difference was seen in the number size
distribution. The CCN model was found to be successful in predicting the
measured CCN concentrations, typically within 25%. A sensitivity study
showed relatively small dependence on the assumption of which model salt
that was used to predict CCN concentrations from H-TDMA data. One strength
of using H-TDMA data to predict CCN concentrations is that the model can
also take into account soluble organic compounds, insofar as they go into
solution at 90% RH. Another advantage is the higher time resolution
compared to using size-resolved chemical composition data. |
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