Abstract
We simulate climate change for the two-year period following the eruption of Mount Pinatubo in the Philippines on June 15, 1991, with the ECHAM4 GCM. The model was forced by realistic aerosol spatial-time distributions and spectral radiative characteristics calculated using Stratospheric Aerosol and Gas Experiment II extinctions and Upper Atmosphere Research Satellite-retrieved effective radii. We calculate statistical ensembles of GCM simulations with and without volcanic aerosols for 2 yr after the eruption for three different SSTs: climatological SST, El Nino-type SST of 1991-1993, and La Nina-type SST of 1984-1986. We performed detailed comparisons of calculated fields with observations. We analyzed the atmospheric response to Pinatubo radiative forcing and the ability of the GCM to reproduce it with different SSTs. The temperature of the tropical lower stratosphere increased by 4 K because of aerosol absorption of terrestrial longwave and solar NIR radiation. The heating is larger than observed, but that is because in this simulation we did not account for quasi-biennial oscillation (QBO) cooling and the cooling effects of volcanically induced ozone depletion. We estimated that both QBO and ozone depletion decrease the stratospheric temperature by about 2 K. The remaining 2 K stratospheric warming is in good agreement with observations. (Author)