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| Titel |
Aerosol optical properties at Lampedusa (Central Mediterranean). 2. Determination of single scattering albedo at two wavelengths for different aerosol types |
| VerfasserIn |
D. Meloni, A. Sarra, G. Pace, F. Monteleone |
| 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 ; 6, no. 3 ; Nr. 6, no. 3 (2006-03-02), S.715-727 |
| Datensatznummer |
250003518
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| Publikation (Nr.) |
 copernicus.org/acp-6-715-2006.pdf |
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| Zusammenfassung |
| Aerosol optical properties were retrieved from direct and diffuse spectral
irradiance measurements made by a multi-filter rotating shadowband
radiometer (MFRSR) at the island of Lampedusa (35.5° N, 12.6° E), in
the Central Mediterranean, in the period July 2001–September 2003. In a
companion paper (Pace et al., 2006) the aerosol optical depth (AOD) and
Ångström exponent were used together with airmass backward
trajectories to identify and classify different aerosol types. The MFRSR
diffuse-to-direct ratio (DDR) at 415.6 nm and 868.7 nm for aerosol
classified as "biomass burning-urban/industrial", originating primarily
from the European continent, and desert dust, originating from the Sahara,
is used in this study to estimate the aerosol single scattering albedo
(SSA). A detailed radiative transfer model is initialised with the measured
aerosol optical depth; calculations are performed at the two wavelengths
varying the SSA values until the modelled DDR matches the MFRSR
observations. Sensitivity studies are performed to estimate how
uncertainties on AOD, DDR, asymmetry factor (g), and surface albedo influence
the retrieved SSA values. The results show that a 3% variation of AOD or
DDR produce a change of about 0.02 in the retrieved SSA value at 415.6 and
868.7 nm; a ±0.06 variation of the asymmetry factor g produces a change
of the estimated SSA of <0.04 at 415.6 nm, and <0.06 at 868.7 nm;
finally, an increase of the assumed surface albedo of 0.05 causes very small
changes (0.01–0.02) in the retrieved SSA. The calculations show that the SSA
of desert dust (DD) increases with wavelength, from 0.81±0.05 at 415.6 nm
to 0.94±0.05 at 868.7 nm; on the contrary, the SSA of
urban/industrial (UN) aerosols decreases from 0.96±0.02 at 415.6 nm to
0.87±0.07 at 868.7 nm; the SSA of biomass burning (BB) particles is
0.82±0.04 at 415.6 nm and 0.80±0.05 at 868.7 nm. Episodes of UN
aerosols occur usually in June and July; long lasting BB aerosol episodes
with large AOD are observed mainly in July and August, the driest months of
the year, when the development of fires is frequent. |
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