Initial fate of fine ash and sulfur from large volcanic eruptions

Abstract

Abstract. Large volcanic eruptions emit huge amounts of sulfur and fine ash into the stratosphere. These products cause an impact on radiative processes, temperature and wind patterns. In simulations with a General Circulation Model including detailed aerosol microphysics, the relation between the impact of sulfur and fine ash is determined for different eruption strengths and locations, one in the tropics and one in high Northern latitudes. Fine ash with effective radii between 1 μm and 15 μm has a lifetime of several days only. Nevertheless, the strong absorption of shortwave and longwave radiation causes additional heating and cooling of ±20 K/day and impacts the evolution of the volcanic cloud. Depending on the location of the volcanic eruption, transport direction changes due to the presence of fine ash, vortices develop and temperature anomalies at ground increase. The results show substantial impact on the local scale but only minor impact on the evolution of sulfate in the stratosphere in the month after the simulated eruptions.

The Interactive Stratospheric Aerosol Model Intercomparison Project (ISA-MIP): motivation and experimental design

“…Some models show a very narrow tropical maximum in comparison to satellite data (e.g., Dhomse et al, 2014) while others show too fast a transport to higher latitudes and fail to reproduce the long persistence of the tropical aerosol reservoir (e.g. Niemeier et al, 2009;English et al, 2013). Sulfate geoengineering studies confirm the importance of the model-dependent meridional transport through the subtropical barrier (e.g.…”

“…More complex methods are size-segregated approaches, such as the modal approach (e.g. Niemeier et al, 2009;Toohey et al, 2011;Brühl et al, 2012;Dhomse et al, 2014;Mills et al, 2016), where the aerosol size distribution is simulated using one or more modes, usually of log-normal shape. The mean radius of each mode of these size distributions varies in time and space.…”

What is the limit of climate engineering by stratospheric injection of SO<sub>2</sub>?

“…Within this stratospheric HAM version we treat only the sulfate aerosol and, apart from the injected SO 2 , only natural sulfur emissions are taken into account in the simulations. Further details are described by Niemeier et al (2009).…”

The role of airborne volcanic ash for the surface ocean biogeochemical iron-cycle: a review

“…The median diameter of ash particles in deep oceanic sediments usually varies between 125 to 63 µm and smaller (Pedersen and Surlyk, 1977). Volcanic fine ash with a particle size smaller than 15 µm can have a lifetime of days to weeks in the stratosphere (Niemeier et al, 2009).…”