Global monitoring of volcanic SO2 degassing with unprecedented resolution from TROPOMI onboard Sentinel-5 Precursor

N Theys,P Hedelt,M Pedergnana,J Vlietinck,S Arellano,D Loyola,C Lerot,C Barrington,B Galle,B Taisne,I De Smedt,D Fernandez,H Yu,H Delgado-Granados,C J M Carlito,M Van Roozendael

doi:10.1038/s41598-019-39279-y

Abstract

Over the last four decades, space-based nadir observations of sulfur dioxide (SO2) proved to be a key data source for assessing the environmental impacts of volcanic emissions, for monitoring volcanic activity and early signs of eruptions, and ultimately mitigating related hazards on local populations and aviation. Despite its importance, a detailed picture of global SO2 daily degassing is difficult to produce, notably for lower-tropospheric plumes, due largely to the limited spatial resolution and coverage or lack of sensitivity and selectivity to SO2 of current (and previous) nadir sensors. We report here the first volcanic SO2 measurements from the hyperspectral TROPOspheric Monitoring Instrument (TROPOMI) launched in October 2017 onboard the ESA’s Sentinel-5 Precursor platform. Using the operational processing algorithm, we explore the benefit of improved spatial resolution to the monitoring of global volcanic degassing. We find that TROPOMI surpasses any space nadir sensor in its ability to detect weak degassing signals and captures day-to-day changes in SO2 emissions. The detection limit of TROPOMI to SO2 emissions is a factor of 4 better than the heritage Aura/Ozone Monitoring Instrument (OMI). Here we show that TROPOMI SO2 daily observations carry a wealth of information on volcanic activity. Provided with adequate wind speed data, temporally resolved SO2 fluxes can be obtained at hourly time steps or shorter. We anticipate that TROPOMI SO2 data will help to monitor global volcanic daily degassing and better understand volcanic processes and impacts.

Highlights

Volcanic emissions of sulfur dioxide can affect significantly atmospheric chemistry and global climate
Note that signal saturation is probably responsible for some differences in the SO2 vertical column densities (VCDs) because the alternative fitting window 325–335 nm is more frequently used for TROPOspheric Monitoring Instrument (TROPOMI) than Ozone Monitoring Instrument (OMI), notably for the pixels close to the source with elevated SO2 columns
Based on global SO2 maps of averaged data over the measurement period, we have investigated all volcanoes reported in the recent volcanic SO2 emissions inventory[28] and found that 58 degassing volcanoes were unambiguously detected in the TROPOMI measurements for the period from November 2017 to July 2018

Summary

Introduction

Volcanic emissions of sulfur dioxide can affect significantly atmospheric chemistry and global climate. Improved methodology to estimate mean SO2 emissions from space measurements has been developed[30] and applied to 10 years of OMI SO2 data over many degassing volcanoes, resulting in the most complete inventory of global volcanic SO2 annual emissions[28] produced so far.

Results

Conclusion