Time-Dependent Behavior of Mount Pinatubo Aerosol

The 15-16 June 1991 eruption of Mount Pinatubo delivered approximately 20 million metric tons of SO2 to the stratosphere. This is about three times the estimate for El Chichon (Bluth et al., 1992). While El Chichon's volcanic plume was confined mostly to the northern hemisphere, the SO2plume from Mount Pinatubo straddled the equator resulting in a more symmetrical global distribution of the H2SO4-H2O aerosol that results from the photochemical conversion of the SO2. Dutton and Christy (1992) find that the average Mount Pinatubo aerosol cloud as measured at two southern and two northern hemisphere sites exceeds the El Chichon aerosol optical depth for the first 10 months by about 70%. This is consistent with the extra SO2 loading and more uniform dispersal of the plume between hemispheres. They found the global and northern hemispheric temperatures of the lower troposphere to be 0.4 and 0.7° C below normal, respectively, by June 1992. This is consistent, thus far, with the predictions of Hansen et al. (1992).