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| Titel |
Aerosol and cloud condensation nuclei formation at Mt. Kleiner Feldberg, Germany |
| VerfasserIn |
R. Kohl, B. Bonn, S. Bourtsoukidis, H. Wex, F. Stratmann, H. Bingemer, W. Haunold, S. Jacobi |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250068171
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| Zusammenfassung |
| New particle formation in number and mass is a quite ubiquous phenomenon in the
atmospheric boundary layer. However, different locations provide different mechanisms for
the initial particle production steps. Investigating the formation aims usually in explaining
two aspects, the initial formation process and the contribution to cloud condensation nuclei
production. In this study we focus on the latter. Once these particles are formed they grow
further on until they reach cloud effective sizes. This is the size, where those particles
can affect local climate via the indirect aerosol effect. This study deals with the
processes mentioned at Mt. Kleiner Feldberg (810 m a.s.l.) about 50 km northwest of
Frankfurt activation diameters. We have been determined using a CCN-counter (DMT,
Boulder, U.S.) [Roberts and Nenes, 2005] and a SMPS (TSI 3936) with a long
DMA (TSI 3081) and a UCPC (TSI 3025A). Particles were assumed to be equal in
chemical composition since the vast majority of particles were smaller than 300 nm in
diameter, i.e. secondary of nature. Therefore, measured CCN concentrations were
intercompared with section wise integrated particle number concentrations starting at
the largest size towards the smaller ones. The best match of integrated and CCN
concentration was assumed to be the activation diameter (Dp,active). With this set-up the
activation diameters were determined for five supersaturations (0.1, 0.2 0.3, 0.4
and 0.6%) during a two weeks period. This resulted in the expected detcrease in
activation size with increasing supersaturation from about 130±10 nm at 0.1%
to 70±5 nm at 0.6% supersaturation. The empirically fitted kappa-value [Petters
and Kreidenweis, 2007] was obtained as 0.16±0.03 indicating aerosols of lower
water-solubility.
Second, measurements of ice nuclei [Klein et al., 2010] were conducted once per day
during the same time period, which indicate that IN concentrations, were about one per mill
of the CCN. Interestingly the cross-correlation between both cloud nuclei indicated at
maximum at the same time, i.e. no time shift, and it was tentatively seen that CCN
concentration pattern could explain 60% of the IN pattern. However the dataset
available is to short to draw final conclusions and more detailed work is needed in the
future.
[1] Klein, H., Nickovic, S., Haunold, W., Bundke, U., Nillius, B., Ebert, M., Weinbruch,
S., Schuetz, L., Levin, Z., Barrie, L. A., and Bingemer, H. (2010): Saharan Dust And Ice
Nuclei Over Central Europe. Atmos. Chem. Phys., 10, 10211–10221.
[2] Petters, M.D., and Kreidenweis, S. M. (2007): A single parameter representation of
hygroscopic growth and cloud condensation nucleus activity. Atmos. Chem. Phys., 7,
1961–1971.
[3] Roberts, G. C., and Nenes, A. (2005): A continuous-flow streamwise thermal-gradient
CCN chamber for atmospheric measurements. In: Aerosol Science and Technology,39,
206-221. |
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