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| Titel |
Development of a new data-processing method for SKYNET sky radiometer observations |
| VerfasserIn |
M. Hashimoto, T. Nakajima, O. Dubovik, M. Campanelli, H. Che, P. Khatri, T. Takamura, G. Pandithurai |
| 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. 11 ; Nr. 5, no. 11 (2012-11-15), S.2723-2737 |
| Datensatznummer |
250003171
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| Publikation (Nr.) |
 copernicus.org/amt-5-2723-2012.pdf |
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| Zusammenfassung |
| In order to reduce uncertainty in the estimation of Direct Aerosol Radiative Forcing (DARF), it is important to improve the estimation of the single
scattering albedo (SSA). In this study, we propose a new data processing
method to improve SSA retrievals for the SKYNET sky radiometer network,
which is one of the growing number of networks of sun-sky photometers, such
as NASA AERONET and others. There are several reports that SSA values from
SKYNET have a bias compared to those from AERONET, which is regarded to be
the most accurate due to its rigorous calibration routines and data quality
and cloud screening algorithms. We investigated possible causes of errors in
SSA that might explain the known biases through sensitivity experiments
using a numerical model, and also using real data at the SKYNET sites at
Pune (18.616° N/73.800° E) in India and Beijing
(39.586° N/116.229° E) in China. Sensitivity
experiments showed that an uncertainty of the order of ±0.03 in the
SSA value can be caused by a possible error in the ground surface albedo or
solid view angle assumed for each observation site. Another candidate for
possible error in the SSA was found in cirrus contamination generated by
imperfect cloud screening in the SKYNET data processing. Therefore, we
developed a new data quality control method to get rid of low quality or
cloud contamination data, and we applied this method to the real observation
data at the Pune site in SKYNET. After applying this method to the
observation data, we were able to screen out a large amount of
cirrus-contaminated data and to reduce the deviation in the SSA value from
that of AERONET. We then estimated DARF using data screened by our new
method. The result showed that the method significantly reduced the
difference of 5 W m−2 that existed between the SKYNET and AERONET values
of DARF before screening. The present study also suggests the necessity of
preparing suitable a priori information on the distribution of coarse
particles ranging in radius between 10 μm and 30 μm for the
analysis of heavily dust-laden atmospheric cases. |
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