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| Titel |
An accuracy assessment of the CALIOP/CALIPSO version 2/version 3 daytime aerosol extinction product based on a detailed multi-sensor, multi-platform case study |
| VerfasserIn |
M. Kacenelenbogen, M. A. Vaughan, J. Redemann, R. M. Hoff, R. R. Rogers, R. A. Ferrare, P. B. Russell, C. A. Hostetler, J. W. Hair, B. N. Holben |
| 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 ; 11, no. 8 ; Nr. 11, no. 8 (2011-04-29), S.3981-4000 |
| Datensatznummer |
250009661
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| Publikation (Nr.) |
 copernicus.org/acp-11-3981-2011.pdf |
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| Zusammenfassung |
| The Cloud Aerosol LIdar with Orthogonal Polarization (CALIOP), on board the
CALIPSO platform, has measured profiles of total attenuated backscatter
coefficient (level 1 products) since June 2006. CALIOP's level 2 products,
such as the aerosol backscatter and extinction coefficient profiles, are
retrieved using a complex succession of automated algorithms. The goal of
this study is to help identify potential shortcomings in the CALIOP version
2 level 2 aerosol extinction product and to illustrate some of the
motivation for the changes that have been introduced in the next version of
CALIOP data (version 3, released in June 2010). To help illustrate the
potential factors contributing to the uncertainty of the CALIOP aerosol
extinction retrieval, we focus on a one-day, multi-instrument, multiplatform
comparison study during the CALIPSO and Twilight Zone (CATZ) validation
campaign on 4 August 2007. On that day, we observe a consistency in the
Aerosol Optical Depth (AOD) values recorded by four different instruments
(i.e. space-borne MODerate Imaging Spectroradiometer, MODIS: 0.67 and
POLarization and Directionality of Earth's Reflectances, POLDER: 0.58,
airborne High Spectral Resolution Lidar, HSRL: 0.52 and ground-based AErosol
RObotic NETwork, AERONET: 0.48 to 0.73) while CALIOP AOD is a factor of two
lower (0.32 at 532 nm). This case study illustrates the following potential
sources of uncertainty in the CALIOP AOD: (i) CALIOP's low signal-to-noise
ratio (SNR) leading to the misclassification and/or lack of aerosol layer
identification, especially close to the Earth's surface; (ii) the cloud
contamination of CALIOP version 2 aerosol backscatter and extinction
profiles; (iii) potentially erroneous assumptions of the aerosol
extinction-to-backscatter ratio (Sa) used in CALIOP's extinction
retrievals; and (iv) calibration coefficient biases in the CALIOP daytime
attenuated backscatter coefficient profiles. The use of version 3 CALIOP
extinction retrieval for our case study seems to partially fix factor (i)
although the aerosol retrieved by CALIOP is still somewhat lower than the
profile measured by HSRL; the cloud contamination (ii) appears to be
corrected; no particular change is apparent in the observation-based CALIOP
Sa value (iii). Our case study also showed very little difference
in version 2 and version 3 CALIOP attenuated backscatter coefficient profiles,
illustrating a minor change in the calibration scheme (iv). |
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