Estimated impact of Agung, El Chichon and Pinatubo volcanic eruptions on global and regional total ozone after adjustment for the QBO

Abstract

Dobson total‐ozone data are used to compare the impact on global and regional total ozone of Agung, El Chichon and Pinatubo volcanic eruptions taking into account the quasi‐biennial oscillation (QBO). This is done by comparing the total‐ozone variation following the 3 eruptions with the average quasi‐biennial variation in total ozone obtained by applying the superposed epoch method to the 13 QBO cycles between 1958 and 1995 which do not include these 3 eruptions. Confidence estimates are based on the 2‐standard‐deviation value of the 13 comparisons. The largest volcanic impact on total ozone is in the European region, with significant (at the 5% level) total‐ozone decreases of about 5% following Agung and El Chichon, and 8% following Pinatubo. The decreases in the north polar zone, Russia, North America and Asia are 5–6% following Pinatubo and 2–3 % following El Chichon. In the tropics the ozone decrease is less than 2% following all 3 eruptions, and there is little consistent impact on south temperate or south polar total ozone. Comparisons are made between these findings and those obtained by others using satellite data.