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| Titel |
Effects of relative humidity on aerosol light scattering and its importance for the comparison of remote sensing with in-situ measurements |
| VerfasserIn |
Paul Zieger, Katrijn Clemer, Selami Yilmaz, Udo Frieß, Hitoshi Irie, Bas Henzing, Rahel Fierz-Schmidhauser, Gerrit de Leeuw, Urs Baltensperger, Ernest Weingartner |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250035721
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| Zusammenfassung |
| In the field, in-situ measurements of aerosol light scattering are often performed under dry
conditions (relative humidity RH < 30-40%) which differ from the ambient ones. Since
ambient aerosol particles experience a hygroscopic growth at enhanced RH, their micro
physical and optical properties - especially the aerosol light scattering - are strongly
dependent on RH. The knowledge of this RH effect is of eminent importance for
climate forcing calculations or for the comparison of remote sensing with in-situ
measurements.
Here, we will present results from the Cabauw Intercomparison Campaign of Nitrogen
Dioxide measuring Instruments (CINDI, June-July 2009, Cabauw, The Netherlands). During
this campaign different remote sensing and in-situ instruments were used to derive
atmospheric parameters mainly NO2 but also aerosol properties. The aerosol in-situ
measurements were performed in the basement of the Cabauw tower (inlet height 60 m). The
aerosol scattering coefficient was measured dry and at various, predefined RH conditions
between 20 and 95% with a recently developed humidified nephelometer (WetNeph) and with
a second nephelometer measuring at dry conditions. In addition, the aerosol absorption
coefficient was measured by a multi-angle absorption photometer (MAAP). This combination
of measurements allows the determination of the aerosol extinction coefficient at ambient
RH.
Three MAX-DOAS (multi-axis differential optical absorption spectroscopy)
instruments retrieved vertical profiles of the aerosol extinction coefficient during CINDI.
The retrieved aerosol extinction corresponding to the lowest profile layer can now
be directly compared to the in-situ value, which is now re-calculated to ambient
RH. |
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