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| Titel |
Can AERONET data be used to accurately model the monochromatic beam and circumsolar irradiances under cloud-free conditions in desert environment? |
| VerfasserIn |
Y. Eissa, P. Blanc, L. Wald, H. Ghedira |
| 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 ; 8, no. 12 ; Nr. 8, no. 12 (2015-12-08), S.5099-5112 |
| Datensatznummer |
250116716
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| Publikation (Nr.) |
 copernicus.org/amt-8-5099-2015.pdf |
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| Zusammenfassung |
| Routine measurements of the beam irradiance at normal incidence include the
irradiance originating from within the extent of the solar disc only
(DNIS), whose angular extent is 0.266° ± 1.7 %, and
from a larger circumsolar region, called the circumsolar normal
irradiance (CSNI). This study investigates whether the spectral aerosol optical
properties of the AERONET stations are sufficient for an accurate modelling
of the monochromatic DNIS and CSNI under cloud-free conditions in a
desert environment. The data from an AERONET station in Abu Dhabi, United
Arab Emirates, and the collocated Sun and Aureole Measurement instrument which
offers reference measurements of the monochromatic profile of solar
radiance were exploited. Using the AERONET data both the radiative transfer
models libRadtran and SMARTS offer an accurate estimate of the monochromatic
DNIS, with a relative root mean square error (RMSE) of 6 % and a
coefficient of determination greater than 0.96. The observed relative bias
obtained with libRadtran is +2 %, while that obtained with SMARTS is
−1 %. After testing two configurations in SMARTS and three in libRadtran
for modelling the monochromatic CSNI, libRadtran exhibits the most accurate
results when the AERONET aerosol phase function is presented as a two-term
Henyey–Greenstein phase function. In this case libRadtran exhibited a
relative RMSE and a bias of respectively 27 and −24 % and a
coefficient of determination of 0.882. Therefore, AERONET data may very well
be used to model the monochromatic DNIS and the monochromatic CSNI. The
results are promising and pave the way towards reporting the contribution of
the broadband circumsolar irradiance to standard measurements of the beam
irradiance. |
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