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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
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Discussion papers
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 14 Dec 2018

Research article | 14 Dec 2018

Review status
This discussion paper is a preprint. A revision of the manuscript is under review for the journal Atmospheric Measurement Techniques (AMT).

iFit: An intensity based retrieval for volcanic SO2 from scattered sunlight UV spectra

Ben Esse1, Mike Burton1, Matthew Varnam1, Ryunosuke Kazahaya2, and Giuseppe Salerno3 Ben Esse et al.
  • 1School of Earth and Environmental Sciences, The University of Manchester, Manchester, M13 9PL, UK
  • 2Japan Meteorological Agency, Tokyo, Japan
  • 3Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Etneo, sezione di Catania, Piazza Roma 2, 95123, Catania, Italy

Abstract. Accurate quantification of the sulphur dioxide (SO2) flux from volcanoes provides both an insight into magmatic processes and a powerful monitoring tool for hazard mitigation, with miniature ultraviolet spectrometers becoming the go-to method for SO2 flux measurements globally. The most common analysis method for these spectrometers is Differential Optical Absorption Spectroscopy (DOAS), in which a reference spectrum taken outside the plume is used to quantify the SO2 column density inside the plume. This can lead to problems if the reference spectrum is contaminated with SO2 as this leads to systematic underestimates in the retrieved SO2 column density. We present a novel method, named “iFit”, which retrieves the SO2 column density from UV spectra by directly fitting the measured intensity spectrum using a high resolution solar reference spectrum. This has a number of advantages over the traditional DOAS method, primarily by eliminating the requirement for a measured reference spectrum. We show that iFit can accurately retrieve SO2 column densities in a series of test cases, finding excellent agreement with existing methods without the use of a reference spectrum. We propose that iFit is well suited to application to both traverse measurements and permanent scanning stations, and shows strong potential for integration into volcano monitoring networks at observatories.

Ben Esse et al.
Interactive discussion
Status: final response (author comments only)
Status: final response (author comments only)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Ben Esse et al.
Model code and software

iFit B. Esse

Ben Esse et al.
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Publications Copernicus
Short summary
This report outlines a new method for measuring sulphur dioxide (SO2) column densities using spectroscopy of scattered sunlight, primarily for measuring the rate of emission of SO2 from volcanoes. iFit gives comparable results to the current main technique without the need for a measured reference spectrum, improving the ease and accuracy with which these measurements are undertaken. iFit would be well suited to deployment in volcano observatories to help improve volcanic SO2 flux measurements.
This report outlines a new method for measuring sulphur dioxide (SO2) column densities using...