PINATUBO ERUPTION WINTER CLIMATE EFFECTS - MODEL VERSUS OBSERVATIONS

Large volcanic eruptions, in addition to the well-known effect of producing global cooling for a year or two, have been observed to produce shorter-term responses in the climate system involving non-linear dynamical processes. In this study, we use the ECHAM2 general circulation model forced with stratospheric aerosols to test some of these ideas. Run in a perpetual-January mode, with tropical stratospheric heating from the volcanic aerosols typical of the 1982 El Chichon eruption or the 1991 Pinatubo eruption, we find a dynamical response with an increased polar night jet in the Northern Hemisphere (NH) and stronger zonal winds which extend down into the troposphere. The Azores High shifts northward with increased tropospheric westerlies at 60-degrees-N and increased easterlies at 30-degrees-N. Surface temperatures are higher both in northern Eurasia and North America, in agreement with observations for the NH winters of 1982-83 and 1991-92 as well as the winters following the other 10 largest volcanic eruptions since 1883.