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dc.contributor.author
Wiacek, Aldona
dc.contributor.author
Peter, Thomas
dc.contributor.author
Lohmann, Ulrike
dc.date.accessioned
2018-09-20T14:03:49Z
dc.date.available
2017-06-09T08:49:47Z
dc.date.available
2018-09-20T14:03:49Z
dc.date.issued
2010
dc.identifier.issn
1680-7375
dc.identifier.issn
1680-7367
dc.identifier.other
10.5194/acp-10-8649-2010
en_US
dc.identifier.uri
http://hdl.handle.net/20.500.11850/28545
dc.identifier.doi
10.3929/ethz-b-000028545
dc.description.abstract
This modelling study explores the availability of mineral dust particles as ice nuclei for interactions with ice, mixed-phase and liquid water clouds, also tracking the particles' history of cloud-processing. We performed 61 320 one-week forward trajectory calculations originating near the surface of major dust emitting regions in Africa and Asia using high-resolution meteorological analysis fields for the year 2007. Dust-bearing trajectories were assumed to be those coinciding with known dust emission seasons, without explicitly modelling dust emission and deposition processes. We found that dust emissions from Asian deserts lead to a higher potential for interactions with high ice clouds, despite being the climatologically much smaller dust emission source. This is due to Asian regions experiencing significantly more ascent than African regions, with strongest ascent in the Asian Taklimakan desert at ~25%, ~40% and 10% of trajectories ascending to 300 hPa in spring, summer and fall, respectively. The specific humidity at each trajectory's starting point was transported in a Lagrangian manner and relative humidities with respect to water and ice were calculated in 6-h steps downstream, allowing us to estimate the formation of liquid, mixed-phase and ice clouds. Downstream of the investigated dust sources, practically none of the simulated air parcels reached conditions of homogeneous ice nucleation (T≲−40 °C) along trajectories that have not experienced water saturation first. By far the largest fraction of cloud forming trajectories entered conditions of mixed-phase clouds, where mineral dust will potentially exert the biggest influence. The majority of trajectories also passed through atmospheric regions supersaturated with respect to ice but subsaturated with respect to water, where so-called "warm ice clouds" (T≳−40 °C) theoretically may form prior to supercooled water or mixed-phase clouds. The importance of "warm ice clouds" and the general influence of dust in the mixed-phase cloud region are highly uncertain due to both a considerable scatter in recent laboratory data from ice nucleation experiments, which we briefly review in this work, and due to uncertainties in sub-grid scale vertical transport processes unresolved by the present trajectory analysis. For "classical" cirrus-forming temperatures (T≲−40 °C), our results show that only mineral dust ice nuclei that underwent mixed-phase cloud-processing, most likely acquiring coatings of organic or inorganic material, are likely to be relevant. While the potential paucity of deposition ice nuclei shown in this work dimishes the possibility of deposition nucleation, the absence of liquid water droplets at T≲−40 °C makes the less explored contact freezing mechanism (involving droplet collisions with bare ice nuclei) highly inefficient. These factors together indicate the necessity of further systematic studies of immersion mode ice nucleation on mineral dust suspended in atmospherically relevant coatings.
en_US
dc.format
application/pdf
en_US
dc.language.iso
en
en_US
dc.publisher
European Geophysical Society
en_US
dc.rights.uri
http://creativecommons.org/licenses/by/3.0/
dc.title
The potential influence of Asian and African mineral dust on ice, mixed-phase and liquid water clouds
en_US
dc.type
Journal Article
dc.rights.license
Creative Commons Attribution 3.0 Unported
dc.date.published
2010-09-16
ethz.journal.title
Atmospheric Chemistry and Physics
ethz.journal.volume
10
en_US
ethz.journal.issue
18
en_US
ethz.journal.abbreviated
Atmos. chem. phys.
ethz.pages.start
8649
en_US
ethz.pages.end
8667
en_US
ethz.version.deposit
publishedVersion
en_US
ethz.identifier.nebis
004294181
ethz.publication.place
Munich
en_US
ethz.publication.status
published
en_US
ethz.leitzahl
ETH Zürich::00002 - ETH Zürich::00012 - Lehre und Forschung::00007 - Departemente::02350 - Dep. Umweltsystemwissenschaften / Dep. of Environmental Systems Science::02717 - Institut für Atmosphäre und Klima / Inst. Atmospheric and Climate Science::03690 - Lohmann, Ulrike / Lohmann, Ulrike
en_US
ethz.leitzahl.certified
ETH Zürich::00002 - ETH Zürich::00012 - Lehre und Forschung::00007 - Departemente::02350 - Dep. Umweltsystemwissenschaften / Dep. of Environmental Systems Science::02717 - Institut für Atmosphäre und Klima / Inst. Atmospheric and Climate Science::03690 - Lohmann, Ulrike / Lohmann, Ulrike
ethz.date.deposited
2017-06-09T08:50:12Z
ethz.source
ECIT
ethz.identifier.importid
imp59364d8b68ba975327
ethz.ecitpid
pub:47670
ethz.eth
yes
en_US
ethz.availability
Open access
en_US
ethz.rosetta.installDate
2017-07-18T10:07:05Z
ethz.rosetta.lastUpdated
2020-02-15T15:07:30Z
ethz.rosetta.exportRequired
true
ethz.rosetta.versionExported
true
ethz.COinS
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