Solar irradiance and total ozone over El Arenosillo (Spain) during the solar eclipse of 3 October 2005 M. Anto ´n a,b,n , A. Serrano a,b , M.L. Cancillo a , J.M. Vaquero a , J.M. Vilaplana c a Departamento de Fı ´sica, Universidad de Extremadura, Badajoz, Spain b Geophysics Centre of E ´ vora (CGE), University of E ´ vora, E ´ vora, Portugal c Estacio ´n de Sondeos Atmosfe ´rico ‘‘El Arenosillo’’, INTA, Huelva, Spain article info Article history: Received 24 November 2009 Received in revised form 24 March 2010 Accepted 25 March 2010 Available online 30 March 2010 Keywords: Eclipse Total irradiance Ultraviolet irradiance Total ozone abstract The ground track of the annular eclipse of 3 October 2005 crossed the Iberian Peninsula. The main objective of this work was to analyze the variability of the solar irradiance and the total ozone column during the course of this event at El Arenosillo (Southwestern Spain). For achieving this goal, two Kipp & Zonen broadband radiometers (one for measuring total solar irradiance and other for measuring ultraviolet erythemal solar irradiance), one NILU-UV multi-band instrument and one Brewer spectro- radiometer were used in this work. Total irradiance (310–2800 nm), and ultraviolet erythemal radiation (UVER) were recorded at a high frequency of 5 s, showing a strong reduction (higher than 80%) of the irradiance at the maximum solar obscuration which was of 79.6%. The irradiance decrease during the course of the eclipse was positively correlated with the percentage of eclipse obscuration, showing a very high agreement (R 2 0.99). The irradiance recorded at selected wavelengths from the NILU-UV instrument shows a more pronounced decrease in the UV irradiance at the lower wavelengths during the solar eclipse. Finally, the evolution of the total ozone column (TOC) derived from Brewer and NILU instruments during the eclipse presented an opposite behavior: while the Brewer derived TOC values increase about 15 DU, the NILU derived TOC values decrease about 11 DU. This opposite behavior is mainly related to an artifact in the spectral irradiances recorded by the two instruments. & 2010 Elsevier Ltd. All rights reserved. 1. Introduction On 3 October 2005 a solar eclipse was visible along a narrow corridor from the North Atlantic, extending across the Iberian Peninsula and Africa and ending in the Indian Ocean. It generated an immense interest in scientific community as well as in general public in Spain since it was the first annular eclipse in the region for over 90 years, providing a great opportunity to investigate the effects of this rare event. The solar limb darkening during the course of the eclipse produces an abrupt and short-time variability in the magnitude and spectral composition of the solar radiation reaching the Earth. The behavior of solar radiation at the Earth’s surface during a solar eclipse (under cloudless sky conditions) is an attractive issue which has been extensively investigated by means of ground-based measurements (e.g. Sharp et al., 1971; Silverman and Mullen, 1975; Fernandez et al., 1993; Beletsky et al., 1998; Mikhalev et al., 1999; Zerefos et al., 2000, 2001; Kazadzis et al., 2007; Kazantzidis et al., 2007; Krezhova et al., 2008). Zerefos et al. (2001) showed that the diffuse component of solar irradiance during a solar eclipse is reduced less than the direct solar irradiance at the shorter wavelengths. Kazadzis et al. (2007) analyzed the spectral effect of the limb darkening on the solar radiation reaching the ground, showing a much more pronounced decrease in the radiation at the shorter wavelengths than at the longer wavelengths. Kazantzidis et al. (2007) showed an inverse behavior occurring for large eclipse magnitude ( 485%), indicat- ing that the spectral radiation at the shortest wavelength (305 nm) decreases less than at the longer wavelengths. In addition to the above, it is very interesting to study the atmosphere’s response to changes in solar forcing during solar eclipses. In this sense, the variability in the total ozone column (TOC) during these events has been also widely described (e.g., Stranz, 1961; Bojkov, 1968, Mims and Mims, 1993; Chakrabarty et al., 1997; Zerefos et al., 2000; Kazadzis et al. 2007). Total ozone measurements derived from Dobson spectroradiometers show a clear increase near the maximum eclipse occultation [e.g., Bojkov, 1968]. In contrast, notable total ozone reductions as measured by Brewer spectroradiometers during the course of solar eclipses have been reported (Zerefos et al., 2000; Kazadzis et al., 2007). These authors suggested that ARTICLE IN PRESS Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/jastp Journal of Atmospheric and Solar-Terrestrial Physics 1364-6826/$ - see front matter & 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.jastp.2010.03.025 n Corresponding author at: Departamento de Fı ´sica, Universidad de Extrema- dura, 06071 Badajoz, Spain. Tel.: + 34 924 289536; fax: + 34 924 289651. E-mail address: mananton@unex.es (M. Anto ´ n). Journal of Atmospheric and Solar-Terrestrial Physics 72 (2010) 789–793