Abstract. Using the Max Planck Institute Grand Ensemble (MPI-GE) with 200
members for the historical simulation (1850–2005), we investigate the impact
of the spatial distribution of volcanic aerosols on the El
Niño–Southern Oscillation (ENSO) response. In
particular, we select three eruptions (El Chichón, Agung and Pinatubo) in
which the aerosol is respectively confined to the Northern Hemisphere, the
Southern Hemisphere or equally distributed across the Equator. Our results
show that relative ENSO anomalies start at the end of the year of the
eruption and peak in the following one. We especially found that when the
aerosol is located in the Northern Hemisphere or is symmetrically
distributed, relative El Niño-like anomalies develop, while aerosol
distribution confined to the Southern Hemisphere leads to a relative La
Niña-like anomaly. Our results point to the volcanically induced
displacement of the Intertropical Convergence Zone (ITCZ) as a key mechanism that drives the ENSO response,
while suggesting that the other mechanisms (the ocean dynamical thermostat and
the cooling of tropical northern Africa or the Maritime Continent)
commonly invoked to explain the post-eruption ENSO response may be less
important in our model.