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Article Dans Une Revue Atmospheric Chemistry and Physics Discussions Année : 2014

Direct quantification of total and biological ice nuclei in cloud water

Résumé

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 suggested their likely significance 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 conditions. Total and biological (i.e. heat sensitive) IN were quantified by droplet-freezing assay between−5◦C and−14◦C. Freezing was systematically induced by the presence of biological material, between−6◦C and−8◦C in 92 % of the samples. Its removal by heat treatment led to a decrease of the temperature of freezing by 3◦C to 4◦C.At−10◦C, there were 0 to∼220 biological IN mL−1 of cloud water (i.e. 0 to ∼22 m−3 of cloudy air based on cloud liquid water content estimates) and these represented 65 % to 100 % of the total IN. Based on back-trajectory plots 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 dataset generated here will help elucidating the role of biological and bacterial IN on cloud’s microphysics by numeric modelling, and their impact on precipitation at local scale.

Dates et versions

hal-01898958 , version 1 (19-10-2018)
hal-01898958 , version 2 (30-10-2020)

Identifiants

Citer

M. Joly, Pierre Amato, Laurent Deguillaume, M. Monier, C. Hoose, et al.. Direct quantification of total and biological ice nuclei in cloud water. Atmospheric Chemistry and Physics Discussions, 2014, 14 (3), pp.3707 - 3731. ⟨10.5194/acpd-14-3707-2014⟩. ⟨hal-01898958v1⟩
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