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Available data of attenuation due to dust from the eruption of Agung Volcano on Bali in March 1963 are compared with turbidity from earlier great eruptions. While abnormal twilights have been observed first in September 1963 in U.S.A., and in November in Europe, measurements of twilight at Weissenau indicate a small increase of stratospheric turbidity already in May 1963. Relevant investigations are summarized.
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Frederic E. Volz (1965) studied this question.
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