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| Titel |
Reconciling aerosol light extinction measurements from spaceborne lidar observations and in situ measurements in the Arctic |
| VerfasserIn |
M. Tesche, P. Zieger, N. Rastak, R. J. Charlson, P. Glantz, P. Tunved, H.-C. Hansson |
| 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 ; 14, no. 15 ; Nr. 14, no. 15 (2014-08-08), S.7869-7882 |
| Datensatznummer |
250118929
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| Publikation (Nr.) |
 copernicus.org/acp-14-7869-2014.pdf |
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| Zusammenfassung |
| In this study we investigate to what degree it is possible to reconcile
continuously recorded particle light extinction coefficients derived from dry
in situ measurements at Zeppelin station (78.92° N,
11.85° E; 475 m above sea level), Ny-Ålesund, Svalbard, that
are recalculated to ambient relative humidity, as well as simultaneous
ambient observations with the Cloud-Aerosol Lidar with Orthogonal
Polarization (CALIOP) aboard the Cloud-Aerosol Lidar and Infrared Pathfinder
Satellite Observations (CALIPSO) satellite. To our knowledge, this represents
the first study that compares spaceborne lidar measurements to optical
aerosol properties from short-term in situ observations (averaged over 5 h)
on a case-by-case basis. Finding suitable comparison cases requires an
elaborate screening and matching of the CALIOP data with respect to the
location of Zeppelin station as well as the selection of temporal and spatial
averaging intervals for both the ground-based and spaceborne observations.
Reliable reconciliation of these data cannot be achieved with the
closest-approach method, which is often used in matching CALIOP observations
to those taken at ground sites. This is due to the transport pathways of the
air parcels that were sampled. The use of trajectories allowed us to
establish a connection between spaceborne and ground-based observations for
57 individual overpasses out of a total of 2018 that occurred in our region
of interest around Svalbard (0 to 25° E, 75 to 82° N) in
the considered year of 2008. Matches could only be established during winter
and spring, since the low aerosol load during summer in connection with the
strong solar background and the high occurrence rate of clouds strongly
influences the performance and reliability of CALIOP observations. Extinction
coefficients in the range of 2 to 130 Mm−1 at 532 nm were found for
successful matches with a difference of a factor of 1.47 (median value for a
range from 0.26 to 11.2) between the findings of in situ and spaceborne
observations (the latter being generally larger than the former). The
remaining difference is likely to be due to the natural variability in
aerosol concentration and ambient relative humidity, an insufficient
representation of aerosol particle growth, or a misclassification of aerosol
type (i.e., choice of lidar ratio) in the CALIPSO retrieval. |
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