Atmopsheric Chemistry of Volcanic Plumes in WRF-Chem

Abstract:

Volcanic eruptions are known to be a strong and concentrated source of reactive halogen species. The chemistry that these species are known to take part in include ozone-destruction cycles. Despite the potentially large perturbation to the chemistry of the troposphere that eruptions may cause the magnitude of such impacts on global and regional scales is largely unknown.
We used WRF-Chem to investigate the influence of Mount Etna on the tropospheric chemistry of the Mediterranean region. The chemistry of bromine, chlorine and mercury has been added to the chemical mechanism CBMZ and we have coupled WRF-Chem with the emissions program PrepChem. We developed a simple parameterisation of the key multiphase reaction cycles involving halogens. Comparison with published field data shows that the model is able to reproduce the bromine explosion phenomenon seen in spectroscopic investigations of volcanic plumes.
From the model results we are able to determine a detailed picture of the chemistry of a volcanic plume; results are presented which show how the character of the volcanic plume evolves as it is advected downwind. We determine the magnitude of Mt. Etna's regional influence under typical conditions. We also present results which show how the variation in volcanic output, as well as meteorological variation within the region, can influence the extent of Mt. Etna's regional impact. As WRF-Chem is very flexible, we also performed model runs fir other volcanoes.. The model results are compared to satellite measurements of BrO and SO2 to improve our understanding of chemical processes in tropospheric volcanic plumes.