Quantitative imaging of volcanic SO 2 plumes with Fabry Pérot Interferometer Correlation Spectroscopy

Abstract. We present first measurements with a novel imaging technique for atmospheric trace gases in the UV spectral range. Imaging Fabry Perot Interferometer Correlation Spectroscopy (IFPICS), employs a Fabry Perot Interferometer (FPI) as wavelength selective element. Matching the FPIs distinct, periodic transmission features to the characteristic differential absorption structures of the investigated trace gas allows to measure differential atmospheric column density (CD) distributions of numerous trace gases, e.g. sulphur dioxide (SO2), bromine monoxide (BrO), or nitrogen dioxide (NO2), with high spatial and temporal resolution. The high specificity in the spectral detection of IFPICS minimises cross interferences to other trace gases and aerosol extinction allowing precise determination of gas fluxes. Furthermore, the instrument response can be modelled using absorption cross sections and a solar atlas spectrum from the literature, thereby avoiding additional calibration procedures, e.g. using gas cells. In a field campaign, we recorded the temporal CD evolution of SO2 in the volcanic plume of Mt. Etna with an integration time of 1 s and 400 × 400 pixels spatial resolution. The first IFPICS prototype can reach a detection limit of 2.1 × 1017 molec cm−2 s−1/2, which is comparable to traditional and much less selective volcanic SO2 imaging techniques.