Atmospheric transport and deposition of Indonesian volcanic emissions

M. A. Pfeffer (1) , B. Langmann (1) , H.-F. Graf (2)

1 Department of the Atmosphere in the Earth System [Hamburg]
2 Department of Geography

A regional climate model study has been performed to investigate the transport and atmospheric loss rates of emissions from Indonesian volcanoes and the sensitivity of these emissions to meteorological conditions and the solubility of the released emissions. Two experiments were conducted: 1) volcanic sulfur released as primarily SO₂ and oxidation to SO₄^2? determined by considering the major tropospheric chemical reactions; and 2) PbCl₂ released as an infinitely soluble passive tracer. The first experiment was used to calculate SO₂ loss rates from each active volcano resulting in an annual mean loss rate for all volcanoes of 1.1×10^?5 s^?1, or an e-folding rate of approximately 1 day. SO₂ loss rate was found to vary seasonally, be poorly correlated with wind speed, and uncorrelated with temperature or relative humidity. The variability of SO₂ loss rates is found to be correlated with the variability of wind speeds, suggesting that it is much more difficult to establish a ''typical'' SO₂ loss rate for volcanoes that are exposed to inconsistent winds. Within an average distance of 69 km away from the active Indonesian volcanoes, 53% of SO₂ is lost due to conversion to SO₄^2?, 42% due to dry deposition, and 5% is lost due to lateral transport away from the dominant direction of plume travel. The solubility of volcanic emissions in water is shown to have a major influence on their atmospheric transport and deposition. High concentrations of PbCl₂ are predicted to be deposited near to the volcanoes while volcanic S travels further away until removal from the atmosphere primarily via the wet deposition of H₂SO₄. The ratio of the concentration of PbCl₂ to SO₂ is found to exponentially decay at increasing distance from the volcanoes. The more rapid removal of highly soluble species should be considered when making observations of SO₂ in an aged plume and relating this concentration to other volcanic species. An assumption that the ratio between the concentrations of highly soluble volcanic compounds and S within an aged plume is equal to that observed in fumarolic gases will result in an overestimation of the atmospheric concentration of highly soluble species.

Domaines: Océan, Atmosphère

M. A. Pfeffer, B. Langmann, H.-F. Graf. Atmospheric transport and deposition of Indonesian volcanic emissions. Atmospheric Chemistry and Physics Discussions, 2005, 5 (6), pp.11861-11897. ⟨hal-00301942⟩