Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 7 5 2007 10.5194/acpd-7-13475-2007 http://www.atmos-chem-phys-discuss.net/7/13475/2007/ http://www.atmos-chem-phys-discuss.net/7/13475/2007/acpd-7-13475-2007.html http://www.atmos-chem-phys-discuss.net/7/13475/2007/acpd-7-13475-2007.pdf 13475 13501 2007-09-14 Attenuation of global ultraviolet and visible irradiance over Greece during the total solar eclipse of 29 March 2006 A. Kazantzidis akaza@auth.gr A. F. Bais C. Emde S. Kazadzis C. S. Zerefos Laboratory of Atmospheric Physics, Aristotle University of Thessaloniki, Thessaloniki, Greece Institut für Physik der Atmosphäre, Deutsches Zentrum für Luft- und Raumfahrt (DLR), Oberpfaffenhofen, 82234 Wessling, Germany National Observatory of Athens, Athens, Greece The variability of ultraviolet and photosynthetically active radiation during the total solar eclipse of 29 March 2006 was examined in this study. The measurements from NILU-UV multichannel actinometers 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 measured changes in UV and visible irradiance were compared with 1-D model calculations (accounting for the limb darkening effect) and differences up 30% were observed for the lower UV wavelengths at high eclipse percentages. The spectral ratios between wavelengths was generally reproduced by the 1-D model, expect for 305 nm, where the irradiance at eclipse percentages of more than 85% decreased with slower rates than for longer wavelengths. As a result, the total ozone, derived from the 305/320 nm ratio, apparently decreased significantly for high eclipse percentages. 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