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| Titel |
Lidar and in situ observations of continental and Saharan aerosol: closure analysis of particles optical and physical properties |
| VerfasserIn |
G. P. Gobbi, F. Barnaba, R. Dingenen, J. P. Putaud, M. Mircea, M. C. Facchini |
| 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 ; 3, no. 6 ; Nr. 3, no. 6 (2003-12-05), S.2161-2172 |
| Datensatznummer |
250001348
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| Publikation (Nr.) |
 copernicus.org/acp-3-2161-2003.pdf |
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| Zusammenfassung |
| Single wavelength polarization lidar observations collected at Mt.\ Cimone
(44.2º N, 10.7º E, 1870 m a.s.l.) during the June 2000 MINATROC campaign are analyzed to derive tropospheric profiles of
aerosol extinction, depolarization, surface area and volume. Lidar retrievals for the
2170-2245 m level are compared to the same variables as computed from in situ measurements of particles size
distributions, performed at the mountain top Station (2165 m a.s.l.) by a differential mobility analyzer
(DMA) and an optical particle counter (OPC). A sensitivity analysis of this closure experiment
shows that mean relative differences between the backscatter coefficients obtained by the two
techniques undergo a sharp decrease when hygroscopic growth to ambient humidity is considered
for the DMA dataset, otherwise representative of dry aerosols. Minimization of differences between
lidar and size distribution-derived backscatter coefficients allowed to find values of the
"best" refractive index, specific to each measurement. These results show the refractive index to increase
for air masses proceeding from Africa and Western Europe. Lidar depolarization was observed to
minimize mainly in airmasses proceeding from Western Europe, thus indicating a spherical,
i.e. liquid nature for such aerosols. Conversely, African, Mediterranean and East Europe aerosol
showed a larger depolarizing fraction, mainly due to coexisting refractory and soluble fractions. The
analysis shows average relative differences between lidar and in-situ observations of
5% for backscatter, 36% for extinction 41% for surface area and 37% for volume. These values are well
within the expected combined uncertainties of the lidar and in situ retrievals. Average differences
further decrease during the Saharan dust transport event, when a lidar signal inversion model
considering non-spherical scatterers is employed. The quality of the closure obtained between
particle counter and lidar-derived aerosol surface area and volume observations constitutes a
validation of the technique adopted to retrieve such aerosol properties on the basis of single-wavelength
lidar observations. |
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