Advances in Quantification of Volcanic SO2 Flux

  • Matthew Varnam

Student thesis: Phd


In this thesis, I outline improvements to UV spectrometer and SO2 camera imagery analyses when observing degassing volcanoes, with the goal of improving the precision and accuracy of volcanic gas emission rate measurements. First, I introduce a new model for radiative transfer under clear conditions, utilising the difference in the SO2 slant column density obtained by fitting the same spectrum with different wavelength windows. At Masaya (Nicaragua), I demonstrate uncorrected measurements underestimate the true column density present by up to five times, sometimes without showing any residual in the standard fit. In addition, diluted measurements are capped, such that increasing the column density present will reduce the uncorrected reading. This means historical measurements at volcanoes made at a distance of several kilometres from the plume may be inaccurate, and in some circumstances may not record correct trends in SO2 emissions. Next, I use the corrected spectrometer column densities to calibrate an SO2 camera, demonstrating good agreement with an improved version of an SO2 camera image-based correction, and validating both with simultaneous traverse measurements. Finally, I adapt the model to examine the effects of SO2 inhomogeneity within the field of view of an instrument, showing that these effects occur in modern satellite observations.
Date of Award1 Aug 2021
Original languageEnglish
Awarding Institution
  • The University of Manchester
SupervisorGrant Allen (Supervisor) & Mike Burton (Supervisor)


  • DOAS
  • spectroscopy
  • radiative transfer
  • UV camera
  • light dilution
  • SO2 emission rate
  • SO2 flux
  • Masaya Volcano
  • volcanic gas

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