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| Titel |
Attenuation of global ultraviolet and visible irradiance over Greece during the total solar eclipse of 29 March 2006 |
| VerfasserIn |
A. Kazantzidis, A. F. Bais, C. Emde, S. Kazadzis, C. S. Zerefos |
| 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 ; 7, no. 23 ; Nr. 7, no. 23 (2007-12-06), S.5959-5969 |
| Datensatznummer |
250005269
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| Publikation (Nr.) |
 copernicus.org/acp-7-5959-2007.pdf |
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| Zusammenfassung |
| The variability of ultraviolet and photosynthetically active radiation (PAR)
during the total solar eclipse of 29 March 2006 was examined in this study.
The measurements from NILU-UV multichannel radiometers at 7 stations of the
Greek UV Network were used, where the maximum eclipse percentage ranged from
73.1% to 94.8%. In addition, an extra instrument was established at a
remote Greek island, Kastelorizo, which was within the Moon's umbral shadow.
The reduction of irradiance at 305 and 312 nm relative to non-eclipse
conditions at all sites was almost 1.5 times more than the corresponding
decrease in the UVA and visible part of the spectrum and reached 98% for
eclipse percentage equal to 94%. The availability of several instruments
in close proximity to the path of the umbral shadow provided a challenging
test for the models. The measured changes in UV and visible irradiance were
compared with 1-D model calculations accounting for the limb darkening
effect. The agreement between measurements and modeled values at all sites
is within 3% for eclipse percentages of less than 30% and becomes
worse as the eclipse progresses. The 1-D model reproduced the spectral
effect of the eclipse in UVA and PAR wavelength regions within 3% for
eclipse percentages up to 50%, but only the half of the observed change
was captured as the eclipse progressed. At three sites, where the eclipse
maximum was more than 94%, the measured irradiance at 305 nm for eclipse
percentages of more than 85% decreased with slower rates than for longer
wavelengths. As a result, the total ozone values, derived from the 305/320 nm ratios, apparently decreased significantly for high eclipse percentages.
The effect is similar at all three sites, but the interpretation of this
observation remains a challenge. Comparison results with 3-D model
calculations shortly before, during and shortly after totality were
performed for the first time and revealed an agreement with measurements
within 20% in the UV-A region. However, the modeled estimates of
irradiance at 312 nm are three times lower than measured values. |
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