Climate model simulation of winter warming and summer cooling following the 1991 Mount Pinatubo volcanic eruption

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 general circulation model (GCM). The model was forced by realistic aerosol spatial-time distributions and spectral radiative characteristics calculated using SAGE II extinctions and UARS-retrieved effective radii. We calculate statistical ensembles of GCM simulations with and without volcanic aerosols for 2 years after the eruption for three different sea surface temperatures (SSTs): climatological SST, El Ni no-type SST of 1991-1993, and La Ni na-type SST of 1984-1986. We performed detailed comparisons of calculated fields with observations. We analyzed the mechanisms of atmospheric response and the ability of the GCM to reproduce them with different SSTs. The temperature of the tropical lower stratosphere increased by 4 K because of aerosol absorption of terrestrial longwave and solar near-infrared radiation. The heating is larger than observed, but that is because in this simulation we did not account for quasibiennial oscillation cooling or the cooling effects of volcanically-induced ozone depletion. By comparing the runs with the Pinatubo aerosol forcing with those with no aerosols, we find that the model calculates a general cooling of the global climate, but with a clear winter warming pattern of surface air temperature over Northern Hemisphere continents. This pattern matches the observed temperature patterns48 refs.Available from TIB Hannover: RR 1347(261) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman