The Southern Oscillation. Part IX: The Influence of Volcanic Eruptions on the Southern Oscillation in the stratosphere

Abstract

The signal in the winter stratosphere on the Northern Hemisphere of a warm event in the Southern Oscillation is a warm polar vortex with a weak westerly circulation. This signal failed to appear in two warm events which took place at the time of the eruptions of Agung and El Chichón. We propose that the volcanic emissions affected the development of the warm events in the stratosphere and support this argument by reference to a sensitivity experiment made by M. Blackmon. This experiment used the observed global anomalies of sea surface temperature in December-January-February 1982/83 but did not consider volcanic aerosols and gasses ejected by El Chichón in 1982. The response of the model stratosphere in the experiment resembled the observed signal of the Southern Oscillation in other years.