Status: this preprint has been withdrawn by the authors.
iFit: An intensity based retrieval for volcanic SO2 from scattered sunlight UV spectra
Ben Esse,Mike Burton,Matthew Varnam,Ryunosuke Kazahaya,and Giuseppe Salerno
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.
This preprint has been withdrawn.
How to cite. Esse, B., Burton, M., Varnam, M., Kazahaya, R., and Salerno, G.: iFit: An intensity based retrieval for volcanic SO2 from scattered sunlight UV spectra, Atmos. Meas. Tech. Discuss. [preprint], https://doi.org/10.5194/amt-2018-404, 2018.
Received: 16 Nov 2018 – Discussion started: 14 Dec 2018
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...