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| Titel |
Columnar aerosol properties from sun-and-star photometry: statistical comparisons and day-to-night dynamic |
| VerfasserIn |
D. Pérez-Ramírez, H. Lyamani, F. J. Olmo, D. N. Whiteman, L. Alados-Arboledas |
| 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 ; 12, no. 20 ; Nr. 12, no. 20 (2012-10-25), S.9719-9738 |
| Datensatznummer |
250011531
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| Publikation (Nr.) |
 copernicus.org/acp-12-9719-2012.pdf |
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| Zusammenfassung |
| This work presents the first analysis of long-term correlative day-to-night
columnar aerosol optical properties. The aim is to better understand
columnar aerosol dynamic from ground-based observations, which are poorly
studied until now. To this end we have used a combination of sun-and-star
photometry measurements acquired in the city of Granada
(37.16° N, 3.60° W, 680 m a.s.l.; South-East
of Spain) from 2007 to 2010. For the whole study period, mean aerosol
optical depth (AOD) around 440 nm (± standard deviation) is
0.18 ± 0.10 and 0.19 ± 0.11 for daytime and nighttime,
respectively, while the mean Angström exponent (α) is
1.0 ± 0.4 and 0.9 ± 0.4 for daytime and nighttime. The ANOVA statistical
tests reveal that there are no significant differences between AOD and
α obtained at daytime and those at nighttime. Additionally, the mean
daytime values of AOD and α obtained during this study period are
coherent with the values obtained in the surrounding AERONET stations. On
the other hand, AOD around 440 nm present evident seasonal patterns
characterised by large values in summer (mean value of 0.20 ± 0.10 both
at daytime and nighttime) and low values in winter (mean value of
0.15 ± 0.09 at daytime and 0.17 ± 0.10 at nighttime). The
Angström exponents also present seasonal patterns, but with low values in
summer (mean values of 0.8 ± 0.4 and 0.9 ± 0.4 at day- and
night-time) and relatively large values in winter (mean values of 1.2 ± 0.4
and 1.0 ± 0.3 at daytime and nighttime). These seasonal patterns
are explained by the differences in the meteorological conditions and by the
differences in the strength of the aerosol sources. To take more insight
about the changes in aerosol particles between day and night, the spectral
differences of the Angström exponent as function of the Angström
exponent are also studied. These analyses reveal increases of the fine mode
radius and of the fine mode contribution to AOD during nighttime, being more
remarkable in the summer seasons. These variations are explained by the
changes of the local aerosol sources and by the meteorological
conditions between daytime and nighttime, as well as aerosol aging
processes. Case studies during summer and winter for different aerosol loads
and types are also presented to clearly illustrate these findings. |
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