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| Titel |
Optical-microphysical properties of Saharan dust aerosols and composition relationship using a multi-wavelength Raman lidar, in situ sensors and modelling: a case study analysis |
| VerfasserIn |
A. Papayannis, R. E. Mamouri, V. Amiridis, E. Remoundaki, G. Tsaknakis, P. Kokkalis, I. Veselovskii, A. Kolgotin, A. Nenes, C. Fountoukis |
| 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. 9 ; Nr. 12, no. 9 (2012-05-07), S.4011-4032 |
| Datensatznummer |
250011117
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| Publikation (Nr.) |
 copernicus.org/acp-12-4011-2012.pdf |
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| Zusammenfassung |
| A strong Saharan dust event that occurred over the city of Athens, Greece
(37.9° N, 23.6° E) between 27 March and 3 April 2009 was
followed by a synergy of three instruments: a 6-wavelength Raman lidar, a
CIMEL sun-sky radiometer and the MODIS sensor. The BSC-DREAM model was used
to forecast the dust event and to simulate the vertical profiles of the
aerosol concentration. Due to mixture of dust particles with low clouds
during most of the reported period, the dust event could be followed by the
lidar only during the cloud-free day of 2 April 2009. The lidar data obtained
were used to retrieve the vertical profile of the optical (extinction and
backscatter coefficients) properties of aerosols in the troposphere. The
aerosol optical depth (AOD) values derived from the CIMEL ranged from
0.33–0.91 (355 nm) to 0.18–0.60 (532 nm), while the lidar ratio (LR)
values retrieved from the Raman lidar ranged within 75–100 sr (355 nm) and
45–75 sr (532 nm). Inside a selected dust layer region, between 1.8 and
3.5 km height, mean LR values were 83 ± 7 and 54 ± 7 sr, at 355
and 532 nm, respectively, while the Ångström-backscatter-related
(ABR355/532) and Ångström-extinction-related (AER355/532)
were found larger than 1 (1.17 ± 0.08 and 1.11 ± 0.02,
respectively), indicating mixing of dust with other particles. Additionally,
a retrieval technique representing dust as a mixture of spheres and spheroids
was used to derive the mean aerosol microphysical properties (mean and
effective radius, number, surface and volume density, and mean refractive
index) inside the selected atmospheric layers. Thus, the mean value of the
retrieved refractive index was found to be
1.49( ± 0.10) + 0.007( ± 0.007)i, and that of the effective
radiuses was 0.30 ± 0.18 μm. The final data set of the
aerosol optical and microphysical properties along with the water vapor
profiles obtained by Raman lidar were incorporated into the ISORROPIA II
model to provide a possible aerosol composition consistent with the retrieved
refractive index values. Thus, the inferred chemical properties showed
12–40% of dust content, sulfate composition of 16–60%, and
organic carbon content of 15–64%, indicating a possible mixing of dust
with haze and smoke. PM10 concentrations levels, PM10 composition
results and SEM-EDX (Scanning Electron Microscope-Energy Dispersive X-ray)
analysis results on sizes and mineralogy of particles from samples during the
Saharan dust transport event were used to evaluate the retrieval. |
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