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Satellite‐based global volcanic SO2 emissions and sulfate direct radiative forcing during 2005–2012
Journal article   Open access   Peer reviewed

Satellite‐based global volcanic SO2 emissions and sulfate direct radiative forcing during 2005–2012

Cui Ge, Jun Wang, Simon Carn, Kai Yang, Paul Ginoux and Nickolay Krotkov
Journal of geophysical research. Atmospheres, Vol.121(7), pp.3446-3464
04/16/2016
DOI: 10.1002/2015JD023134
url
https://doi.org/10.1002/2015JD023134View
Published (Version of record) Open Access

Abstract

An 8 year volcanic SO2 emission inventory for 2005–2012 is obtained based on satellite measurements of SO2 from OMI (Ozone Monitoring Instrument) and ancillary information from the Global Volcanism Program. It includes contributions from global volcanic eruptions and from eight persistently degassing volcanoes in the tropics. It shows significant differences in the estimate of SO2 amount and injection height for medium to large volcanic eruptions as compared to the counterparts in the existing volcanic SO2 database. Emissions from Nyamuragira (DR Congo) in November 2006 and Grímsvötn (Iceland) in May 2011 that were not included in the Intergovernmental Panel on Climate Change 5 (IPCC) inventory are included here. Using the updated emissions, the volcanic sulfate (SO42−) distribution is simulated with the global transport model Goddard Earth Observing System (GEOS)‐Chem. The simulated time series of sulfate aerosol optical depth (AOD) above 10 km captures every eruptive volcanic sulfate perturbation with a similar magnitude to that measured by Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO). The 8 year average contribution of eruptive SO42− to total SO42− loading above 10 km is ~10% over most areas of the Northern Hemisphere, with a maxima of 30% in the tropics where the anthropogenic emissions are relatively smaller. The persistently degassing volcanic SO42− in the tropics barely reaches above 10 km, but in the lower atmosphere it is regionally dominant (60%+ in terms of mass) over Hawaii and other oceanic areas northeast of Australia. Although the 7 year average (2005–2011) of eruptive volcanic sulfate forcing of −0.10 W m−2 in this study is comparable to that in the 2013 IPCC report (−0.09 W m−2), significant discrepancies exist for each year. Our simulations also imply that the radiative forcing per unit AOD for volcanic eruptions can vary from −40 to −80 W m−2, much higher than the −25 W m−2 implied in the IPCC calculations. In terms of sulfate forcing efficiency with respect to SO2 emission, eruptive volcanic sulfate is 5 times larger than anthropogenic sulfate. The sulfate forcing efficiency from degassing volcanic sources is close to that of anthropogenic sources. This study highlights the importance of characterizing both volcanic emission amount and injection altitude as well as the key role of satellite observations in maintaining accurate volcanic emissions inventories. Key Points New global 2005‐2012 volcanic SO2 inventory from OMI and SO42− direct radiative forcing from GEOS‐Chem The new emission inventory is more complete than the existing one for large volcanic eruptions IPCC's volcanic sulfate radiative forcing efficiency (with respect to AOD) has a factor of 2‐4 low bias
 direct radiative forcing volcanic degassing injection height OMI SO2 volcanic sulfate aerosols volcanic emission inventory

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