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| Titel |
Evaluating CALIPSO's 532 nm lidar ratio selection algorithm using AERONET sun photometers in Brazil |
| VerfasserIn |
F. J. S. Lopes, E. Landulfo, M. A. Vaughan |
| 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 ; 6, no. 11 ; Nr. 6, no. 11 (2013-11-28), S.3281-3299 |
| Datensatznummer |
250085120
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| Publikation (Nr.) |
 copernicus.org/amt-6-3281-2013.pdf |
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| Zusammenfassung |
| Since the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations
(CALIPSO) satellite first began probing the Earth's atmosphere on
13 June 2006, several research groups dedicated to investigating the
atmosphere's optical properties have conducted measurement campaigns to
validate the CALIPSO data products. Recently, in order to address the lack of
CALIPSO validation studies in the Southern Hemisphere, and especially the
South American continent, the Lasers Environmental Applications Research
Group at Brazil's Nuclear and Energy Research Institute (IPEN) initiated
efforts to assess CALIPSO's aerosol lidar ratio estimates using the AERONET
sun photometers installed at five different locations in Brazil. In this
study we develop a validation methodology to evaluate the accuracy of the
modeled values of the lidar ratios used by the CALIPSO extinction algorithms.
We recognize that the quality of any comparisons between satellite and
ground-based measurements depends on the degree to which the instruments are
collocated, and that even selecting the best spatial and temporal matches
does not provide an unequivocal guarantee that both instruments are measuring
the same air mass. The validation methodology presented in this study
therefore applies backward and forward air mass trajectories in order to
obtain the best possible match between the air masses sampled by the
satellite and the ground-based instruments, and thus reduces the
uncertainties associated with aerosol air mass variations. Quantitative
comparisons of lidar ratios determined from the combination of AERONET
optical depth measurements and CALIOP integrated attenuated backscatter
measurements show good agreement with the model values assigned by the CALIOP
algorithm. These comparisons yield a mean percentage difference of
−1.5% ± 24%. This result confirms the accuracy in the lidar
ratio estimates provided by the CALIOP algorithms over Brazil to within an
uncertainty range of no more than 30%. |
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