After the volcanic eruption of El Chich¿n in 1982, the distribution of volcanic aerosols in the upper atmosphere was zonally very inhomogeneous for about a month or more and was located in a fairly uniform zonal band around the Earth in the northern subtropical region for the ensuing several months. The impact of those aerosols absorbing radiation on the atmospheric motion is discussed in the model of Gill (1980). It is shown that the mean westerly wind induced near the central Pacific equatorial region would be able to trigger or amplify the El Ni¿o Southern Oscillation. Several observed results related to the simulation are discussed in some detail. The location of the initial center of most aerosols relative to the central Pacific is important in the model, and the impact of the forcing at the Agung event of 1963 is estimated to be smaller than that of the present event, which seems to agree with observed results. ¿ American Geophysical Union 1988