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| Titel |
Midlatitude cirrus classification at Rome Tor Vergata through a multichannel Raman–Mie–Rayleigh lidar |
| VerfasserIn |
D. Dionisi, P. Keckhut, G. L. Liberti, F. Cardillo, F. Congeduti |
| 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. 23 ; Nr. 13, no. 23 (2013-12-09), S.11853-11868 |
| Datensatznummer |
250085860
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| Publikation (Nr.) |
 copernicus.org/acp-13-11853-2013.pdf |
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| Zusammenfassung |
A methodology to identify and characterize cirrus clouds has been developed
and applied to the multichannel-multiwavelength Rayleigh–Mie–Raman (RMR)
lidar in Rome Tor Vergata (RTV). A set of 167 cirrus cases, defined on the
basis of quasi-stationary temporal period conditions, has been selected in a
data set consisting of about 500 h of nighttime lidar sessions acquired
between February 2007 and April 2010. The derived lidar parameters
(effective height, geometrical and optical thickness and mean
back-scattering ratio) and the cirrus mid-height temperature (estimated from
the radiosonde data of Pratica di Mare, WMO, World Meteorological Organization, site no. 16245) of this sample
have been analyzed by the means of a clustering multivariate analysis. This
approach identified four cirrus classes above the RTV site: two thin cirrus
clusters in mid- and upper troposphere and two thick cirrus clusters in
mid-upper troposphere. These results, which are very similar to those
derived through the same approach at the lidar site of the Observatoire de
Haute-Provence (OHP), allows characterization of cirrus clouds over the RTV site and
attests to the robustness of such classification.
To acquire some indications about the cirrus generation methods for the
different classes, analyses of the extinction-to-backscatter ratio
(lidar ratio, LReff, in terms of frequency distribution functions
and dependencies on the mid-height cirrus temperature, have been performed. A
preliminary study relating some meteorological parameters (e.g., relative
humidity, wind components) to cirrus clusters has also been conducted.
The RTV cirrus results, recomputed through the cirrus classification by
Sassen and Cho (1992), show good agreement with other midlatitude lidar
cirrus observations for the relative occurrence of subvisible (SVC), thin and
opaque cirrus classes (10%, 49% and 41%, respectively). The overall
mean value of cirrus optical depth is 0.37 ± 0.18, while most
retrieved LReff values range between 10–60 sr, and the estimated
mean value is 31 ± 15 sr, similar to LR values of lower latitude
cirrus measurements.
The obtained results are consistent with previous studies conducted with
different systems and confirm that cirrus classification based on a
statistical approach seems to be a good tool both to validate the
height-resolved cirrus fields calculated by models and to investigate the
key processes governing cirrus formation and evolution. However, the lidar
ratio and optical depth analyses are affected by some uncertainties (e.g.,
lidar error noise, multiple scattering effects, supercooled water clouds)
that reduce the confidence of the results. Future studies are needed to
improve the characterization of the cirrus optical properties and, thus, the
determination of their radiative impact. |
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