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| Titel |
Microphysical and optical properties of Arctic mixed-phase clouds. The 9 April 2007 case study. |
| VerfasserIn |
J.-F. Gayet, G. Mioche, A. Dörnbrack, A. Ehrlich, A. Lampert, M. Wendisch |
| 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 ; 9, no. 17 ; Nr. 9, no. 17 (2009-09-10), S.6581-6595 |
| Datensatznummer |
250007620
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| Publikation (Nr.) |
 copernicus.org/acp-9-6581-2009.pdf |
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| Zusammenfassung |
| Airborne measurements in Arctic boundary-layer stratocumulus were carried out
near Spitsbergen on 9 April 2007 during the Arctic Study of Tropospheric
Aerosol, Clouds and Radiation (ASTAR) campaign. A unique set of co-located
observations is used to describe the cloud properties, including detailed in
situ cloud microphysical and radiation measurements along with airborne and
co-located spaceborne remote sensing data (CALIPSO lidar and CloudSat radar).
CALIPSO profiles indicate cloud top levels at temperature between
−24°C and −21°C. In situ measurements confirm that the
cloud-top lidar attenuated backscatter signal along the aircraft trajectory
is linked with the presence of liquid water, a common feature observed in
Arctic mixed-phase stratocumulus clouds. A low concentration of large ice
crystals is also observed up to the cloud top resulting in significant
CloudSat radar echoes. Since the ratio of the extinction of liquid water
droplets to ice crystals is high, broadband radiative effects near the cloud
top are mostly dominated by water droplets. CloudSat observations and in situ
measurements reveal high reflectivity factors (up to 15 dBZ) and
precipitation rates (1 mm h−1). This feature results from efficient
ice growth processes. About 25% of the theoretically available liquid water
is converted into ice water with large precipitating ice crystals. Using an
estimate of mean cloud cover, a considerable value of
106 m3 h−1 of fresh water could be settled over the Greenland
sea pool. European Centre for Medium-Range Weather Forecast (ECMWF)
operational analyses reproduces the boundary layer height variation along the
flight track. However, small-scale features in the observed cloud field
cannot be resolved by ECMWF analysis. Furthermore, ECMWF's diagnostic
partitioning of the condensed water into ice and liquid reveals serious
shortcomings for Arctic mixed-phased clouds. Too much ice is modelled. |
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