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| Titel |
Systematic satellite observations of the impact of aerosols from passive volcanic degassing on local cloud properties |
| VerfasserIn |
S. K. Ebmeier, A. M. Sayer, R. G. Grainger, T. A. Mather, E. Carboni |
| 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. 19 ; Nr. 14, no. 19 (2014-10-09), S.10601-10618 |
| Datensatznummer |
250119086
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| Publikation (Nr.) |
 copernicus.org/acp-14-10601-2014.pdf |
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| Zusammenfassung |
| The impact of volcanic emissions, especially from passive degassing and minor
explosions, is a source of uncertainty in estimations of aerosol indirect
effects. Observations of the impact of volcanic aerosol on clouds contribute
to our understanding of both present-day atmospheric properties and of the
pre-industrial baseline necessary to assess aerosol radiative forcing. We
present systematic measurements over several years at multiple active and
inactive volcanic islands in regions of low present-day aerosol burden. The
time-averaged indirect aerosol effects within 200 km downwind of island
volcanoes are observed using Moderate Resolution Imaging Spectroradiometer
(MODIS, 2002–2013) and Advanced Along-Track Scanning Radiometer (AATSR,
2002–2008) data. Retrievals of aerosol and cloud properties at Kīlauea
(Hawai'i), Yasur (Vanuatu) and Piton de la Fournaise (la Réunion) are
rotated about the volcanic vent to be parallel to wind direction, so that
upwind and downwind retrievals can be compared. The emissions from all three
volcanoes – including those from passive degassing, Strombolian activity and
minor explosions – lead to measurably increased aerosol optical depth downwind
of the active vent. Average cloud droplet effective radius is lower downwind of the
volcano in all cases, with the peak difference ranging from 2–8 μm
at the different volcanoes in different seasons. Estimations of the
difference in Top of Atmosphere upward Short Wave flux upwind and downwind of
the active volcanoes from NASA's Clouds and the Earth's Radiant Energy System
(CERES) suggest a downwind elevation of between 10 and 45 Wm−2 at
distances of 150–400 km from the volcano, with much greater local
(< 80 km) effects. Comparison of these observations with cloud
properties at isolated islands without degassing or erupting volcanoes
suggests that these patterns are not purely orographic in origin. Our
observations of unpolluted, isolated marine settings may capture processes
similar to those in the pre-industrial marine atmosphere. |
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