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| Titel |
Physical and optical properties of aerosols over an urban location in Spain: seasonal and diurnal variability |
| VerfasserIn |
H. Lyamani, F. J. Olmo, 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 ; 10, no. 1 ; Nr. 10, no. 1 (2010-01-13), S.239-254 |
| Datensatznummer |
250007903
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| Publikation (Nr.) |
 copernicus.org/acp-10-239-2010.pdf |
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| Zusammenfassung |
| Measurements of aerosol optical properties and aerosol number size
distribution obtained during the period from December 2005 to November 2007
at Granada, an urban site in south-eastern Spain, are analyzed. Large
variations of the measured variables have been found, and related to
variations in emissions sources and meteorological conditions. High values
of aerosol absorption and scattering coefficients are obtained during winter
and low values are measured during summer. This seasonal pattern in the
surface aerosol optical properties is opposite to the seasonal cycle showed
by columnar aerosol optical depth. The differences in the seasonal features
of the surface and column-integrated data are related to seasonal variations
in the aerosol vertical distribution, aerosol sources and boundary layer
height. In winter the number density of "fine" particles (0.5<particle
diameter<1 μm) is significantly larger than in summer while the
number density of "coarse" particles (1<particle diameter<20 μm)
is slightly larger during summer and spring than during winter and autumn.
The scattering Angström exponent, αs, presents an evident
seasonal cycle with values of 1.8±0.2, 1.6±0.3, 1.3±0.3 and
1.4±0.3 in winter, spring, summer and autumn, respectively. This
suggests the presence of a large fraction of submicron particles at the
site, especially during winter. The aerosols measured in this study contain
a large fraction of absorbing material as indicated by the average
single-scattering albedo that has values of 0.65±0.07, 0.66±0.06,
0.70±0.06 and 0.73±0.06 in autumn, winter, spring and summer,
respectively. The aerosol scattering albedo obtained in the surface boundary
layer of Granada is below the critical value of 0.86 that determines the
shift from cooling to warming. These results put in evidence the need of
efforts to reduce absorbing particles (black carbon) emissions to avoid the
possible warming that would result from the reductions of the cooling
aerosols only. The aerosol absorption and scattering coefficients present a
clear diurnal pattern, in all seasons, with two local maxima, one early in
the morning and the second one in the evening. This diurnal cycle is mainly
attributed to the diurnal evolution of atmospheric boundary layer and local
anthropogenic activities. |
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