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| Titel |
Absorption properties of Mediterranean aerosols obtained from multi-year ground-based remote sensing observations |
| VerfasserIn |
M. Mallet, O. Dubovik, P. Nabat, F. Dulac, R. Kahn, J. Sciare, D. Paronis, J. F. Léon |
| 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. 18 ; Nr. 13, no. 18 (2013-09-16), S.9195-9210 |
| Datensatznummer |
250085694
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| Publikation (Nr.) |
 copernicus.org/acp-13-9195-2013.pdf |
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| Zusammenfassung |
| Aerosol absorption properties are of high importance to assess aerosol impact
on regional climate. This study presents an analysis of aerosol absorption
products obtained over the Mediterranean basin or land stations in the region
from multi-year ground-based AERONET observations with a focus on the
Absorbing Aerosol Optical Depth (AAOD), Single Scattering Albedo (SSA) and
their spectral dependence. The AAOD and Absorption Angström Exponent (AAE)
dataset is composed of daily averaged AERONET level 2 data from a total of
22 Mediterranean stations having long time series, mainly under the influence
of urban-industrial aerosols and/or soil dust. This dataset covers the 17-yr
period 1996–2012 with most data being from 2003–2011 (~89% of
level-2 AAOD data). Since AERONET level-2 absorption products require a high
aerosol load (AOD at 440 nm > 0.4), which is most often
related to the presence of desert dust, we also consider level-1.5 SSA data,
despite their higher uncertainty, and filter out data with an Angström
exponent < 1.0 in order to study absorption by carbonaceous
aerosols. The SSA dataset includes AERONET level-2 products. Sun-photometer
observations show that values of AAOD at 440 nm vary between
0.024 ± 0.01 (resp. 0.040 ± 0.01) and 0.050 ± 0.01
(0.055 ± 0.01) for urban (dusty) sites. Analysis shows that the
Mediterranean urban-industrial aerosols appear "moderately" absorbing with
values of SSA close to ~0.94–0.95 ± 0.04 (at 440 nm) in most
cases except over the large cities of Rome and Athens, where aerosol appears
more absorbing (SSA ~0.89–0.90 ± 0.04). The aerosol Absorption
Angström Exponent (AAE, estimated using 440 and 870 nm) is found to be
larger than 1 for most sites over the Mediterranean, a manifestation of
mineral dust (iron) and/or brown carbon producing the observed absorption.
AERONET level-2 sun-photometer data indicate a possible East-West gradient,
with higher values over the eastern basin
(AAEEast = 1.39/AAEWest = 1.33). The North-South
AAE gradient is more pronounced, especially over the western basin. Our
additional analysis of AERONET level-1.5 data also shows that organic
absorbing aerosols significantly affect some Mediterranean sites. These
results indicate that current climate models treating organics as
nonabsorbing over the Mediterranean certainly underestimate the warming
effect due to carbonaceous aerosols. |
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