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| Titel |
Ice nuclei measurements at a high altitude remote station in the Northern Apennines |
| VerfasserIn |
Jann Schrod, Heinz Bingemer, Werner Haunold, Joachim Curtius, Stefano Decesari, Angela Marinoni, Matteo Rinaldi, Paolo Bonasoni, Paolo Cristofanelli |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250073322
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| Zusammenfassung |
| During a field campaign of the PEGASOS (Pan-European Gas-AeroSOls-climate interactions
Study, http://pegasos.iceht.forth.gr/) project in June 2012 we have made daily ice nucleus
measurements on top of the Monte Cimone (44.18Ë N, 10.70Ë E, 2165 m asl) in the
Northern Apennines at the “O. Vittori” Climate Observatory. Samples were taken
at this GAW-WMO Global Station in a six hour rhythm (4 a.m., 10 a.m., 4 p.m.
and 10 p.m.) and at increased frequency during specific events (e.g. dust transport
episodes).
Ice nuclei were measured by an offline technique. Aerosol particles of 40 liters of air were
collected by electrostatic precipitation on a silicon substrate. Subsequently the ice nuclei were
analyzed in the vacuum diffusion chamber FRIDGE [Klein et al. 2010] (FRankfurt Ice Nuclei
Deposition FreezinG Experiment) by exposing the particles to supersaturation with respect to
ice (106 % to 119 %) at -8 Ë C, -13 Ë C and -18 Ë C. In our setup ice nuclei are activated in
deposition and condensation freezing modes. A camera detects and counts ice crystals grown
on ice nuclei. Every ice crystal counted is assumed to represent at least one ice
nucleus.
The mean IN concentration at Mt. Cimone was 60 IN per liter (at -18 Ë C and 119%
relative humility over ice), significantly higher than a longstanding mean at Mt.
Kleiner Feldberg (30 IN/l), Germany for June. A mean active site density (IN per
surface area of large aerosol particles) of 2.3 * 109 m-2 was calculated. The origin
of the air masses sampled was established based on backward trajectories. With
more than 100 IN/l on average (at -18Ë C and 119% relative humility over ice) the
samples originating from North Africa were highest, and activated fractions were
4 to 20 times higher than for other transport sectors. An intensive event of dust
transport was recorded by several instruments in the middle of June. At its peak in the
morning of the 21st of June large aerosol surface and mass concentrations were
observed by an optical particle sizer. A clear increase of submicron particles was
noted during the passage of the dust plume. The heavily dust loaded air had high IN
concentrations up to 270 IN/l . The maximum fraction of large aerosol particles
activated as ice nuclei during this dust event was one ice nucleus in 1250 aerosol
particles.
Acknowledgements: This work was funded by Deutsche Forschungsgemeinschaft (DFG)
under the Research Unit INUIT.
References
[Klein et al. 2010] Klein, H. ; Haunold, W. ; Bundke, U. ; Nillius, B. ; Wetter, T. ;
Schallenberg, S. ; Bingemer, H.: A new method for sampling of atmospheric ice nuclei with
subsequent analysis in a static diffusion chamber. In: Atmospheric Research 96 (2010), p. 218
– 224. |
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