Southern Hemisphere Atmospheric Circulation Effects of the 1991 Mount Pinatubo Eruption

1 Global average cooling and Northern Hemisphere winter warming are well-known 2 climatic responses to the June 15, 1991 eruption of the Mount Pinatubo volcano in the 3 Philippines. Here we investigate the Southern Hemisphere response. Using National Centers for 4 Environmental Prediction/National Center for Atmospheric Research Reanalysis, European 5 Centre for Medium-Range Weather Forecasting Reanalysis, and simulations with the National 6 Aeronautics and Space Administration Goddard Institute for Space Studies ModelE climate 7 model, we find that, in contrast to the Northern Hemisphere, there were no strong significant 8 anomalies in atmospheric circulation in the Southern Hemisphere. We examined 50 mb and 500 9 mb circulation patterns, as well as the Southern Hemisphere Annular Mode index, and found no 10 consistent significant anomalies associated with the volcanic eruption, or the previous large 11 volcanic eruptions of the past 50 years, the 1963 Agung and 1982 El Chichón eruptions. The 12 few anomalies that occurred after Pinatubo are consistent with patterns found during an El Niño 13 event, which took place that same year. 14