Relevance of a Detailed Volcanic Injection Source in Global Model Simulations: a Sensitivity Study

Simulations of volcanic plume dispersal are needed to assess potential atmospheric and climate impacts. The evolution of the resulting volcanic plume depends on the details of the eruption itself, such as the chemical composition of the emitted mixture, the vertical profile of the injection, and the temporal distribution of the volcanic pulses. Global atmospheric and climate models generally represent volcanic eruptions with a simplified spatio-temporal profile; a typical example of a volcanic injection parameterization is a uniform or gaussian vertical profile between specified altitudes in the column of grid boxes above the location of the volcano. To explore the sensitivity of the long range volcanic plume evolution to the injection details, we coupled the output of the three-dimensional numerical model ASHEE (Ash Equilibrium Eulerian Model), which describes the injection of a mixture of solid particles (i.e., pyroclasts) and volcanic gases (i.e., water) from a vent into a stratified atmosphere, with the NASA Goddard Earth Observing System Chemistry Climate Model (GEOS CCM), which simulates the long range transport of the volcanic plume and the microphysical evolution of the aerosol particles. Here, we present results from a range of sensitivity tests that explore the impact of specific volcanic source functions on the dispersal of the volcanic plume and its microphysical evolution, to highlight the relevance of the injection specifications at different horizontal resolution and time scales.