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| Titel |
Quantification of ice nuclei active at near 0 °C temperatures in low-altitude clouds at the Puy de Dôme atmospheric station |
| VerfasserIn |
M. Joly, P. Amato, L. Deguillaume, M. Monier, C. Hoose, A.-M. Delort |
| 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 ; 14, no. 15 ; Nr. 14, no. 15 (2014-08-14), S.8185-8195 |
| Datensatznummer |
250118949
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| Publikation (Nr.) |
 copernicus.org/acp-14-8185-2014.pdf |
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| Zusammenfassung |
| The distribution, abundance and nature of ice nucleation active particles in
the atmosphere are major sources of uncertainty in the prediction of cloud
coverage, precipitation patterns and climate. Some biological ice nuclei (IN)
induce freezing at temperatures at which most other atmospheric particles
exhibit no detectable activity (> −10 °C). Their actual
contribution to the pool of IN in clouds remains poorly known, but numerical
studies have suggested a probable significance of biological IN in atmospheric
processes. In this study, cloud water was collected aseptically from the
summit of Puy de Dôme (1465 m a.s.l., France) within contrasted
meteorological and physico-chemical situations. Total and biological (i.e.
heat-sensitive) IN were quantified by droplet-freezing assay between
−5 °C and −14 °C. We observed that freezing was
systematically induced by biological material, between −6 °C and
−8 °C in 92% of the samples. Its removal by heat treatment
consistently led to a decrease of the onset freezing temperature, by
3 °C or more in most samples. At −10 °C, 0 to
~ 220 biological IN mL−1 of cloud water were measured (i.e. 0
to ~ 22 m−3 of cloud air based on cloud liquid water content
estimates), and these represented 65% to 100% of the total IN. Based on
back-trajectories and on physico-chemical analyses, the high variability
observed resulted probably from a source effect, with IN originating mostly
from continental sources. Assuming that biological IN were all bacteria, at
maximum 0.6% of the bacterial cells present in cloud water samples could
have acted as IN at −8 °C, 1.5% at −10 °C, and
3.1% at −12 °C. The data set generated here will help elucidate
the role of biological and bacterial IN on cloud microphysics by numeric
modelling, and their impact on precipitation at local scale. |
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