Measuring global volcanic degassing with the Ozone Monitoring Instrument (OMI)

Abstract

Abstract The ultraviolet (UV) Ozone Monitoring Instrument (OMI), launched on NASA's Aura satellite in July 2004, was the first space-based sensor to provide operational sulphur dioxide (SO 2 ) measurements (OMSO2) for use by the scientific community. Herein, we discuss the application of OMSO2 data for the monitoring of global volcanic SO 2 emissions, with an emphasis on lower tropospheric volcanic plumes. We review the algorithms used to produce OMSO2 data and highlight some key measurement sensitivity issues. The data processing scheme used to generate web-based OMSO2 data subsets for volcanic regions and estimate SO 2 burdens in volcanic plumes is outlined. We describe three techniques to derive SO 2 emission rates from the OMSO2 measurements, and employ one method (using single OMI pixels to estimate SO 2 fluxes) to elucidate SO 2 flux detection thresholds on a global scale. Applications of OMSO2 data to volcanic degassing studies are demonstrated using four case studies. These examples show how OMSO2 measurements correlate with changes in eruptive activity at Kilauea volcano (Hawaii), constrain small, potentially significant SO 2 releases from reawakening, historically inactive volcanoes, track long-term changes in SO 2 degassing from Nyiragongo volcano (D.R. Congo), and detect SO 2 emissions from the remote Lastarria Volcano (Chile), in the actively deforming Lazufre region.