Abstract
Abstract The Mt. Pinatubo eruptions in June 1991 were some of the largest of this century. In addition to causing devastating local effects, they injected large quantities of particles and gases, especially sulfur dioxide, SO 2 , straight into the middle atmosphere. In this paper we present and discuss simultaneous observations of stratospheric O 3 and SO 2 carried out at Cuiaba (16.0 °S, 56.0 °W), Brazil, where an automated Brewer spectrophotometer is operated on a routine basis. The data presented cover both the pre- and post-eruption conditions (October 1990–August 1994). Also, some complementary total ozone observations carried out at Cachoeira Paulista (22.7 °S, 45.0 °W) and Natal (5.8 °S, 35.2 °W) in Brazil have been used in this report. After about two weeks of the major eruption (early July), a strong enhancement (factor of six) in the column SO 2 observations was detected at Cuiaba. The enhanced SO 2 levels continued for about two and half months. The total ozone observations at Cuiaba showed a significant (11%) decrease in the stratospheric ozone levels during the winter months in 1992, possibly associated in part with delayed volcanic injection effects in the stratosphere.
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