The ozone variations during the solar eclipse of 20 May 1966

Abstract

During the annular (87.6 %) solar eclipse of May 20, 1966, more than 60 measurements of total ozone were taken with the Dobson ozonespectrophotometer at the University of Sofia, Bulgaria. An analysis of data obtained shows an ozone increase of 26-30 m atm-cm (An > 2an) at the maximum phase of the eclipse. However, according to the photochemical theory, only -1 m atm-cm increase should occur during an eclipse such as this.The difference between the theoretical and observed increase of the total ozone may be partly due to the limb-darkening effect. The importance of this effect increases progressively to the maximum phase of the eclipse. When dark-limb correction is applied to observational data, the ozone increase is reduced to 14 m atm-cm (about 4 per cent of the total ozone amount). This increase is as yet unexplained.

Fluctuation in ozone column over Ahmedabad during the solar eclipse of 24 October 1995

“…According to Hunt [ 1965], uncorrected and limb darkening corrected observations of total ozone during an eclipse differ at the most by 0.1%. Bojkov [ 1968] showed that even after applying limb darkening corrections the variation of total ozone during the solar eclipse of 20 May 1966 could not be explained. We, therefore, have not applied this correction in our calculation of ozone column.…”

“…Variation of ozone during a solar eclipse is one such case. There have been several reported studies of this effect; the first critical review of these studies was by Bojkov [1968]. He also took observations with a Dobson spectrophotometer during the annular (88%) solar eclipse of 20 May 1966 in Bulgaria (42ø N, 23 ø E).…”

“…During the eclipse this ratio changes due to the limb darkening of the solar disk [Sevensson, 1958]. Bojkov [1968] calculated the change in this ratio during different phases of the eclipse. He found that this ratio initially increased by -0.20 % for -a 30 % of the obscuration of solar disk, and then decreased by -7 % when the obscuration of the solar disk was -92 %.…”

Theoretically determined multiple‐scattering effects of dust on Umkehr observations

“…If the haze-effect curve becomes positive near 90" it would have the effect of reducing the amount of ozone in the levels near 30km and above given in the Umkehr evaluation system. In turn, this would tend to bring Umkehr results in slightly better agreement with direct observations of ozone distribution near 30km (Bojkov 1966;Craig et al 1967). Should more refined correction techniques be desired, it will be necessary to have some knowledge of the refractive indices of dust, perhaps as they vary with season and location.…”

Ozone and NO2 variations measured during the 1 August 2008 solar eclipse above Eureka, Canada with a UV‐visible spectrometer

“…Ozone measurements during eclipses have yielded a variety of results. Brewer and Dobson spectrophotometers have measured both significant increases and decreases in ozone during solar eclipses [e.g., Bojkov , 1968; Chakrabarty et al , 2001]. Many of these studies account for the effect of the changing solar spectrum (limb darkening), which is only on the order of 0.01% [ Kazadzis et al , 2007], but they do not account for the effects of diffuse radiation during eclipses, which can cause artificial decreases in Brewer and Dobson vertical column densities (VCDs) of up to 30 Dobson units (DU) [ Zerefos et al , 2000].…”