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| Titel |
Analysis of co-located MODIS and CALIPSO observations near clouds |
| VerfasserIn |
T. Várnai, A. Marshak |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1867-1381
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 5, no. 2 ; Nr. 5, no. 2 (2012-02-17), S.389-396 |
| Datensatznummer |
250002465
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| Publikation (Nr.) |
 copernicus.org/amt-5-389-2012.pdf |
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| Zusammenfassung |
This paper aims at helping synergistic studies in combining data from
different satellites for gaining new insights into two critical yet poorly
understood aspects of anthropogenic climate change, aerosol-cloud
interactions and aerosol radiative effects. In particular, the paper
examines the way cloud information from the MODIS (MODerate resolution
Imaging Spectroradiometer) imager can refine our perceptions based on CALIOP
(Cloud-Aerosol Lidar with Orthogonal Polarization) lidar measurements about
the systematic aerosol changes that occur near clouds.
The statistical analysis of a yearlong dataset of co-located global maritime
observations from the Aqua and CALIPSO (Cloud-Aerosol Lidar and Infrared
Pathfinder Satellite Observation) satellites reveals that MODIS's
multispectral imaging ability can greatly help the interpretation of CALIOP
observations. The results show that imagers on Aqua and CALIPSO yield very
similar pictures, and that the discrepancies – due mainly to wind drift and
differences in view angle – do not significantly hinder aerosol measurements
near clouds. By detecting clouds outside the CALIOP track, MODIS reveals
that clouds are usually closer to clear areas than CALIOP data alone would
suggest. The paper finds statistical relationships between the distances to
clouds in MODIS and CALIOP data, and proposes a rescaling approach to
statistically account for the impact of clouds outside the CALIOP track even
when MODIS cannot reliably detect low clouds, for example at night or over
sea ice. Finally, the results show that the typical distance to clouds
depends on both cloud coverage and cloud type, and accordingly varies with
location and season. In maritime areas perceived cloud free, the global
median distance to clouds below 3 km altitude is in the 4–5 km range. |
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