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| Titel |
Relationships between particles, cloud condensation nuclei and cloud droplet activation during the third Pallas Cloud Experiment |
| VerfasserIn |
T. Anttila, D. Brus, A. Jaatinen, A.-P. Hyvärinen, N. Kivekäs, S. Romakkaniemi, M. Komppula, H. Lihavainen |
| 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 ; 12, no. 23 ; Nr. 12, no. 23 (2012-12-03), S.11435-11450 |
| Datensatznummer |
250011639
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| Publikation (Nr.) |
 copernicus.org/acp-12-11435-2012.pdf |
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| Zusammenfassung |
| Concurrent measurement of aerosols, cloud condensation nuclei (CCN) and cloud
droplet activation were carried out as a part of the third Pallas Cloud
Experiment (PaCE-3) which took place at a ground based site located on
northern Finland during the autumn of 2009. In this study, we investigate
relationships between the aerosol properties, CCN and size resolved cloud
droplet activation. During the investigated cloudy periods, the inferred
number of cloud droplets (CDNC) varied typically between 50 and
150 cm−3 and displayed a linear correlation both with the number of
particles having sizes over 100 nm and with the CCN concentrations at
0.4% supersaturation. Furthermore, the diameter corresponding to the
50% activation fraction, D50, was generally in the range of 80 to 120
nm. The measured CCN concentrations were compared with predictions of a
numerical model which used the measured size distribution and size resolved
hygroscopicity as input. Assuming that the droplet surface tension is equal
to that of water, the measured and predicted CCN concentrations were
generally within 30%. We also simulated size dependent cloud droplet
activation with a previously developed air parcel model. By forcing the model
to reproduce the experimental values of CDNC, adiabatic estimates for the
updraft velocity and the maximum supersaturation reached in the clouds were
derived. Performed sensitivity studies showed further that the observed
variability in CDNC was driven mainly by changes in the particle size
distribution while the variations in the updraft velocity and hygroscopicity
contributed to a lesser extent. The results of the study corroborate
conclusions of previous studies according to which the number of cloud
droplets formed in clean air masses close to the Arctic is determined mainly
by the number of available CCN. |
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