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A comparison of satellite- and ground-based measurements of SO2 emissions from tungurahua volcano, Ecuador

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McCormick, BT 
Yang, J 
Mather, TA 


jats:titleAbstract</jats:title>jats:pSatellite‐measured SOjats:sub2</jats:sub> mass loadings and ground‐based measurements of SOjats:sub2</jats:sub> emission rate are not directly comparable, with ∼40% differences between mean emissions reported by each technique from Tungurahua volcano, Ecuador, during late 2007. Numerical simulations of postemission processing and dispersal of Tungurahua's SOjats:sub2</jats:sub> emissions enable more effective comparison of ground‐ and satellite‐based SOjats:sub2</jats:sub> data sets, reducing the difference between them and constraining the impact of plume processing on satellite SOjats:sub2</jats:sub> observations. Ground‐based measurements of SOjats:sub2</jats:sub> emission rate are used as the model input, and simulated SOjats:sub2</jats:sub> mass loadings are compared to those measured by the Ozone Monitoring Instrument (OMI). The changing extent of SOjats:sub2</jats:sub> processing has a significant impact on daily variation in SOjats:sub2</jats:sub> mass loading for a fixed volcanic emission rate. However, variations in emission rate at Tungurahua are large, suggesting that overall volcanic source strength and not subsequent processing is more likely to be the dominant control on atmospheric mass loading. SOjats:sub2</jats:sub> emission rate estimates are derived directly from the OMI observations using modeled SOjats:sub2</jats:sub> lifetime. Good agreement is achieved between both observed and simulated mass loadings (∼21%) and satellite‐derived and ground‐measured SOjats:sub2</jats:sub> emission rates (∼18%), with a factor of 2 improvement over the differences found by simple direct comparison. While the balance of emission source strength and postemission processing will differ between volcanoes and regions, under good observation conditions and where SOjats:sub2</jats:sub> lifetime is ∼24 hours, satellite‐based sensors like OMI may provide daily observations of SOjats:sub2</jats:sub> mass loading which are a good proxy for volcanic source strength.</jats:p>



volcanic degassing, remote sensing, atmospheric chemistry, modeling, Tungurahua, sulphur dioxide

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Journal of Geophysical Research

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American Geophysical Union (AGU)
B.T.M. acknowledges funding from the National Centre for Earth Observation, part of the UK’s Natural Environment Research Council, and latterly the Deep Carbon Observatory and the Smithsonian Institution. B.T.M., M.E., and T.A.M. are supported by and contribute to the NERC NCEO Dynamic Earth and Geohazards group. S.A.C. acknowledges funding from NASA through grants NNX09AJ40G (Aura Validation), NNX10AG60G (Atmospheric Chemistry Modeling and Analysis Program), and NNX11AF42G (Aura Science Team). J.Y. was funded by the Isaac Newton Trust at the University of Cambridge for the duration of this project. The authors thank Anja Schmidt and two anonymous reviewers for their thorough and constructive comments. We acknowledge the Goddard Earth Sciences Data and Information Services Center for making OMI SO2 data publicly available.