A one and half year interactive MA/ECHAM4 simulation of Mount Pinatubo Aerosol

The Mount Pinatubo volcanic eruption in June 1991 had significant impact on stratospheric and tropospheric climate and circulation. Enhanced radiative heating caused by the aerosol absorption of solar and terrestrial radiatio n changed stratospheric temperature and circulation. Using the stratospheri c mesospheric version of the Hamburg climate model MA/ECHAM4, we performed an interactive Pinatubo simulation with prognostic stratospheric aerosol. I nteractive and noninteractive model results for the years 1991 and 1992 are compared with satellite data and in situ measurements. The on-line calcula ted heating rates are in good agreement with radiation transfer models indi cating maximum heating rates of about 0.3 K/d in October 1991. The dynamic feedback in the MA/ECHAM4 simulation is similar to observations. The model is able to reproduce the strengthening of the polar vortex in winter 1991/1 992 and a minor warming in January. The importance of an interactive treatm ent of the volcanic cloud for the aerosol transport is evidenced by the ana lysis of effects such as aerosol lifting and meridional transport. In gener al, the model results agree well with observations from the northern midlat itudes, especially in the first months after the eruption. The MA/ECHAM4 mo del is successful in reproducing the formation of two distinct maxima in th e optical depth but is unable to simulate the persistence of the tropical a erosol reservoir from the end of 1991. Better agreement may be achieved if the influence of the quasi-biennial oscillation and ozone changes is also t aken into account.