Monitoring of volcanic sulphur dioxide emissions using differential absorption lidar (DIAL), differential optical absorption spectroscopy (DOAS), and correlation spectroscopy (COSPEC)

• The total fluxes of sulphur dioxide from the Italian volcanoes Etna, Stromboli, and Vulcano were studied using optical remote sensing techniques in three shipborne field experiments (1992, 1994, and 1997). The main purpose of the experiments was to compare active (laser) techniques with passive monitoring. Differential absorption lidar (DIAL) measurements were implemented by placing the Swedish mobile lidar system on board the Italian research vessel Urania, sailing under the volcanic plumes. Simultaneously, the passive differential optical absorption spectroscopy (DOAS) technique was used for assessing the total overhead gas burden. Finally, correlation spectroscopy (COSPEC) was also implemented in one of the campaigns. Differences in integrated gas column assessment are expected and observed, mostly connected to complex scattering conditions influencing the passive measurements. Since such measurements are much employed in routine volcanic monitoring it is of great interest to model and provide corrections to the raw data obtained. Lidar measurements proved to be quite useful for this purpose. By combining the integrated gas concentration over the plume cross section with wind velocity data, SO2 fluxes of the order of 1000, 100, and 10 tonnes/day were measured for Mt. Etna, Stromboli, and Vulcano, respectively.

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NATURVETENSKAP  -- Fysik -- Atom- och molekylfysik och optik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Atom and Molecular Physics and Optics (hsv//eng)

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