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© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 09 May 2019

Research article | 09 May 2019

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This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Chemistry and Physics (ACP).

Revisiting the Agung 1963 volcanic forcing – impact of one or two eruptions

Ulrike Niemeier1, Claudia Timmreck1, and Kirstin Krüger2 Ulrike Niemeier et al.
  • 1Max Planck Institute for Meteorology, Bundesstr. 53, 20146 Hamburg, Germany
  • 2Department of Geosciences, University of Oslo, Blindern, 0315 Oslo, Norway

Abstract. In 1963 a series of eruptions of Mt. Agung, Indonesia, resulted in the 3rd largest eruption of the 20th century and claimed about 1900 lives. Two eruptions of this series injected SO2 into the stratosphere, a requirement to get a long lasting stratospheric sulfate layer. The first eruption on March 17th injected 4.7 Tg SO2 into the stratosphere, the second eruption 2.3 Tg SO2 on May, 16th. In recent volcanic emission data sets these eruption phases are merged together to one large eruption phase for Mt. Agung in March 1963 with an injection rate of 7 Tg SO2. The injected sulfur forms a sulfate layer in the stratosphere. The evolution of sulfur is non-linear and depends on the injection rate and aerosol background conditions. We performed ensembles of two model experiments, one with a single and a second one with two eruptions. The two smaller eruptions result in a lower burden, smaller particles and 0.1 to 0.3 Wm−2 (10–20 %) lower radiative forcing in monthly mean global average compared to the individual eruption experiment. The differences are the consequence of slightly stronger meridional transport due to different seasons of the eruptions, lower injection height of the second eruption and the resulting different aerosol evolution.

The differences between the two experiments are significant but smaller than the variance of the individual ensemble means. Overall, the evolution of the volcanic clouds is different in case of two eruptions than with a single eruption only. We conclude that there is no justification to use one eruption only and both climatic eruptions should be taken into account in future emission datasets.

Ulrike Niemeier et al.
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Ulrike Niemeier et al.
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Short summary
In 1963 Mt. Agung, Indonesia, was unrest for several month. During this period, two medium-size eruptions injected SO2 into the stratosphere. Recent volcanic emission data sets include only one large eruption phase. The evolution of sulfur is non-linear. Therefore, we compared model experiments, with a) one larger eruption and b) two eruptions as observed. The evolution of the volcanic cloud differs significantly between the two experiments and both climatic eruptions are necessary.
In 1963 Mt. Agung, Indonesia, was unrest for several month. During this period, two medium-size...