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Abstract

We use this model to simulate the global distribution of volcanic aerosols after the eruption of El Chichon in Mexico in April 1982. The simulated background aerosol distributions are highly dispersed, while a slight latitudinal gradient is also noticed. The calculated background aerosol surface area and mass are about 0.7 to 1.0 μm2/cm3 and 0.3 to 0.5 parts per billion by mass, respectively, at midlatitude in the northern hemisphere, in fair agreement with available observations. After the eruption of El Chichon in April 1982, the stratospheric aerosol load rapidly increases in the tropics at an altitude of 20 to 25 km. The aerosol area in the tropics reaches a maximum 50 μm2/cm3 in the lower stratosphere, which is about 70-100 times the background aerosol area. We find that for a model simulation in which the gas phase SO2 is the only material ejected by the eruption, the model substantially underestimates the volcanic aerosol load. Thus we expect that the direct ejection of sulfate aerosol particles may be a very important process. -Authors