Volcanic SO 2 fluxes derived from satellite data: a survey using OMI, GOME-2, IASI and MODIS
Sulphur dioxide (SO
2) fluxes of active degassing volcanoes are routinely measured with ground-based equipment to characterize and monitor volcanic activity. SO
2 of unmonitored volcanoes or from explosive volcanic eruptions, can be measured with satellites. However, remote-sensing methods based on absorption spectroscopy generally provide integrated amounts of already dispersed plumes of SO
2 and satellite derived flux estimates are rarely reported.
Here we review a number of different techniques to derive volcanic SO 2 fluxes using satellite measurements of plumes of SO 2 and investigate the temporal evolution of the total emissions of SO 2 for three very different volcanic events in 2011: Puyehue-Cordón Caulle (Chile), Nyamulagira (DR Congo) and Nabro (Eritrea). High spectral resolution satellite instruments operating both in the ultraviolet-visible (OMI/Aura and GOME-2/MetOp-A) and thermal infrared (IASI/MetOp-A) spectral ranges, and multispectral satellite instruments operating in the thermal infrared (MODIS/Terra-Aqua) are used. We show that satellite data can provide fluxes with a sampling of a day or less (few hours in the best case). Generally the flux results from the different methods are consistent, and we discuss the advantages and weaknesses of each technique. Although the primary objective of this study is the calculation of SO 2 fluxes, it also enables us to assess the consistency of the SO 2 products from the different sensors used.