Stratospheric Aerosol Simulated by EMAC Using MIPAS SO2 for Estimate of Volcanic Injections and SAGE and OSIRIS Satellite Data for Evaluation in the Period 2002-2011

Abstract:

Multiyear studies with the chemistry climate model EMAC with the comprehensive aerosol module GMXE for troposphere and stratosphere demonstrate that the sulfur gases COS and SO₂, the latter mostly from low-latitude and midlatitude volcanic eruptions, control the formation of stratospheric aerosol. TOMS and OMI satellite data are used to estimate the upper limit of injected SO₂-mass and the location of the volcano while the spatial distribution of the SO₂ plume some days after the eruption is taken taken from MIPAS on ENVISAT. A comparison of simulated stratospheric optical depth with the timeseries of values observed by SAGE and OSIRIS at different latitudes shows that it is important to include every low latitude volcano that reaches more than about 15km altitude, but also big midlatitude ones where injection heights above about 13km matter for the global stratosphere. Our simulations also show that organic and black carbon from biomass burning contribute significantly to extinction and radiative heating in the lower stratosphere. Despite its optimization for the stratosphere concerning the size distributions, the aerosol module approximately reproduces the observed total optical depth and the distribution of the different aerosol types in the troposphere.
This study is part of the SPARC SSIRC activities.