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| Titel |
Transport of aerosol to the Arctic: analysis of CALIOP and French aircraft data during the spring 2008 POLARCAT campaign |
| VerfasserIn |
G. Ancellet, J. Pelon, Y. Blanchard, B. Quennehen, A. Bazureau, K. S. Law, A. Schwarzenboeck |
| 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. 16 ; Nr. 14, no. 16 (2014-08-18), S.8235-8254 |
| Datensatznummer |
250118953
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| Publikation (Nr.) |
 copernicus.org/acp-14-8235-2014.pdf |
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| Zusammenfassung |
| Lidar and in situ observations performed during the Polar Study using
Aircraft, Remote Sensing, Surface Measurements and Models, Climate,
Chemistry, Aerosols and Transport (POLARCAT) campaign are reported here in
terms of statistics to characterize aerosol properties over northern Europe
using daily airborne measurements conducted between Svalbard and Scandinavia
from 30 March to 11 April 2008. It is shown that during this period a rather
large number of aerosol layers was observed in the troposphere, with a
backscatter ratio at 532 nm of 1.2 (1.5 below 2 km, 1.2 between 5 and 7 km
and a minimum in between). Their sources were identified using multispectral
backscatter and depolarization airborne lidar measurements after careful
calibration analysis. Transport analysis and comparisons between in situ and
airborne lidar observations are also provided to assess the quality of this
identification. Comparison with level 1 backscatter observations of the
spaceborne Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) were
carried out to adjust CALIOP multispectral observations to airborne
observations on a statistical basis. Recalibration for CALIOP daytime
1064 nm signals leads to a decrease of their values by about 30%,
possibly related to the use of the version 3.0 calibration procedure. No
recalibration is made at 532 nm even though 532 nm scattering ratios appear
to be biased low (−8%) because there are also significant differences in
air mass sampling between airborne and CALIOP observations. Recalibration of
the 1064 nm signal or correction of −5% negative bias in the 532 nm
signal both could improve the CALIOP aerosol colour ratio expected for this
campaign. The first hypothesis was retained in this work. Regional analyses
in the European Arctic performed as a test emphasize the potential of the
CALIOP spaceborne lidar for further monitoring in-depth properties of the
aerosol layers over Arctic using infrared and depolarization observations.
The CALIOP April 2008 global distribution of the aerosol backscatter reveal
two regions with large backscatter below 2 km: the northern Atlantic between
Greenland and Norway, and northern Siberia. The aerosol colour ratio increases
between the source regions and the observations at latitudes above 70° N
are consistent with a growth of the aerosol size once transported to the Arctic.
The distribution of the aerosol optical properties in the mid-troposphere
supports the known main transport pathways between the mid-latitudes and the
Arctic. |
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