Robock et al. (1995)
Robock, Alan, Karl E. Taylor, Georgiy L. Stenchikov, and
Yuhe Liu, 1995: GCM evaluation of a mechanism for El
the El Chichón ash cloud. Geophys.
Res. Lett., 22, 2369-2372.
The El Chichón volcanic eruption in 1982 was immediately
followed by the strongest El Niño of the century in 1982-83.
We investigate a possible mechanism proposed
by Hirono whereby volcanic eruptions might
trigger or enhance El Niños.
Three distributions for volcanic ash aerosol in the
used to force simulations with a modified version of the
NCAR CCM1 atmospheric general circulation model for the
month of April 1982, using observed sea surface
Only in the case of mid-tropospheric heating is there a
strong dynamical reaction in the atmosphere resulting in a
weakening of the trade winds consistent with surface wind observations
north of the Equator in the eastern Pacific Ocean, and with the first
part of Hirono's theory. However, the 1982 ENSO event had started before this
wind anomaly, and only trade wind collapses in the western equatorial
Pacific can initiate El Niños.
The results suggest that the timing and location of the El Chichón
eruption and the large ENSO event that followed was a coincidence, and that
Hirono's mechanism was not responsible for the strength or timing of the
Prepared by Alan Robock (email@example.com ) -
Last updated on April 21, 1999