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An Accuracy Assessment of the CALIOP/CALIPSO Version 2/Version 3 Daytime Aerosol Extinction Product Based on a Detailed Multi-Sensor, Multi-Platform Case StudyThe 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. spaceborne 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).
Document ID
20110014214
Acquisition Source
Langley Research Center
Document Type
Reprint (Version printed in journal)
External Source(s)
doi:10.5194/acp-11-3981-2011
Authors
Kacenelenbogen, M. (NASA Ames Research Center Moffett Field, CA, United States)
Vaughan, M. A. (NASA Langley Research Center Hampton, VA, United States)
Redemann, J. (Bay Area Environmental Research Inst. Sonoma , CA, United States)
Hoff, R. M. (Maryland Univ. Baltimore County Baltimore, MD, United States)
Rogers, R. R. (NASA Langley Research Center Hampton, VA, United States)
Ferrare, R. A. (NASA Langley Research Center Hampton, VA, United States)
Russell, P. B. (NASA Ames Research Center Moffett Field, CA, United States)
Hostetler, C. A. (NASA Langley Research Center Hampton, VA, United States)
Hair, J. W. (NASA Langley Research Center Hampton, VA, United States)
Holben, B. N. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Date Acquired
August 25, 2013
Publication Date
April 29, 2011
Publication Information
Publication: Atmospheric Chemistry and Physics
Publisher: Copernicus Publications
Volume: 11
Subject Category
Geophysics
Report/Patent Number
NF1676L-12740
Funding Number(s)
WBS: WBS 653967.04.12.01
Distribution Limits
Public
Copyright
Public Use Permitted.

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