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| Titel |
Effects of relative humidity on aerosol light scattering: results from different European sites |
| VerfasserIn |
P. Zieger, R. Fierz-Schmidhauser, E. Weingärtner, U. Baltensperger |
| 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 ; 13, no. 21 ; Nr. 13, no. 21 (2013-11-01), S.10609-10631 |
| Datensatznummer |
250085782
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| Publikation (Nr.) |
 copernicus.org/acp-13-10609-2013.pdf |
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| Zusammenfassung |
| The effect of aerosol water uptake on the aerosol particle light
scattering coefficient (σsp) is described in this
study by comparing measurements from five European sites: the
Jungfraujoch, located in the Swiss Alps at 3580 m a.s.l.;
Ny-Ålesund, located on Spitsbergen in the Arctic; Mace Head,
a coastal site in Ireland; Cabauw, a rural site in the Netherlands; and
Melpitz, a regional background site in Eastern Germany. These sites
were selected according to the aerosol type usually encountered at
that location. The scattering enhancement factor f(RH, λ) is
the key parameter to describe the effect of water uptake on the
particle light scattering. It is defined as the
σsp(RH) at a certain relative humidity (RH) and
wavelength λ divided by its dry value. f(RH) at the five sites
varied widely, starting at very low values of
f(RH = 85%, λ = 550 nm) around 1.28 for mineral
dust, and reaching up to 3.41 for Arctic aerosol. Hysteresis behavior was observed at
all sites except at the Jungfraujoch (due to the absence of sea
salt). Closure studies and Mie simulations showed that both size and
chemical composition determine the magnitude of f(RH). Both
parameters are also needed to successfully predict f(RH). Finally,
the measurement results were compared to the widely used aerosol model,
OPAC (Hess et al., 1998). Significant discrepancies were seen, especially at
intermediate RH ranges; these were mainly attributed to inappropriate
implementation of hygroscopic growth in the OPAC model. Replacement of the
hygroscopic growth with values from the recent literature resulted in a clear
improvement of the OPAC model. |
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