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| Titel |
Measurement of relative humidity dependent light scattering of aerosols |
| VerfasserIn |
R. Fierz-Schmidhauser, P. Zieger, G. Wehrle, A. Jefferson, J. A. Ogren, U. Baltensperger, E. Weingärtner |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1867-1381
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 3, no. 1 ; Nr. 3, no. 1 (2010-01-21), S.39-50 |
| Datensatznummer |
250000812
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| Publikation (Nr.) |
 copernicus.org/amt-3-39-2010.pdf |
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| Zusammenfassung |
Relative humidity (RH) influences the water content of aerosol particles and
therefore has an important impact on the particles' ability to scatter
visible light. The RH dependence of the particle light scattering coefficient
(σsp is therefore an important measure for climate forcing
calculations. We built a humidification system for a nephelometer which
allows the measurement of σsp at a defined RH in the range of
40–90%. This RH conditioner consists of a humidifier followed by a dryer,
which enables us to measure the hysteresis behavior of deliquescent aerosol
particles.
In this paper we present the set-up of a new humidified nephelometer, a
detailed characterization with well defined laboratory generated aerosols,
and a first application in the field by comparing our instrument to another
humidified nephelometer.
Monodisperse ammonium sulfate and sodium chloride particles were measured at
four different dry particle sizes. Agreement between measurement and
prediction based on Mie theory was found for both σsp and
f(RH)=σsp(RH)/σsp(dry) within the range of
uncertainty. The two humidified nephelometers measuring at a rural site in
the Black Forest (Germany) often detected different f(RH), probably
caused by the aerosol hysteresis behavior: when the aerosol was metastable,
therefore was scattering more light, only one instrument detected the higher
f(RH). |
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