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| Titel |
Impact of activation process on fog life cycle |
| VerfasserIn |
Marie Mazoyer, Frederic Burnet, Christine Lac, Greg Roberts, Jean-Charles Dupont, Martial Haeffelin, Thierry Elias |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250110090
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| Publikation (Nr.) |
 EGU/EGU2015-10055.pdf |
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| Zusammenfassung |
| Fogs are complex meteorological system dealing with fine scale processes. Subtle
interaction between radiative, dynamic, turbulent and microphysic processes can
lead to different fog life cycle, which make prediction difficult. The droplets that
composed fogs are formed trough the activation of aerosol particles called CCN (cloud
condensation nuclei) described by the Köhler theory (Köhler, 1936). The number and
distribution of the droplets activated during fog formation is determined by the
aerosols particles properties and number and the ambient vapor supersaturation of the
atmosphere.
In the frame of the PreViBOSS project, an in-situ measurement platform of fog
properties at ground level was deployed at SIRTA (Instrumented Site for Atmospheric
Remote Sensing Research) during winter 2010 to 2013. Microphysics data supply a
detailed characterization of number size spectrum from dry to wet aerosols particles
and inform on the abilities of the aerosols particles to act as a CCN. 48 fog events
have been studied. Supersaturation critical values and concentrations of CCN have
been determined and linked to aerosols properties. The main impact of aerosols
size distribution on activation have been pointed out. The study of droplets spectra
evolution reveals the major physical processes into fogs and suggests that even if
thermodynamic dominates the fog life cycle, activation process seems to have a significant
effect.
Large eddy simulation of fog run with Meso-NH model allow to explore precisely the
interaction between fog physical processes and to quantify activation impact. Supersaturation
modelling is a key point, a new pseudo-prognostic scheme (Thouron et al., 2012) is
used.
Confrontation between a detailed experimental study and three-dimensional fine scale
simulation in LES provides an accurate investigation of the impact of activation process on
fog life cycle. |
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