Spectroscopic Observation of Volcanic Emissions – Status and Future Trends

Paper i proceeding, 2011

In recent years spectroscopic quantification of gas emissions from volcanoes made considerable progress. In particular spectroscopic approaches observing volcanic gases in the ultra-violet spectral range evolved from an art to mature techniques, which are routinely applicable in automated installations. Using spatio-temporal correlation techniques also absolute amouts of trace gas fluxes can be determined. This is e.g. demonstrated by the NOVAC network. In addition systems operating in the infra-red (IR) spectral range have also made enormous progress. Here two varieties are in use: Absorption spectroscopy using direct sunlight and Emission spectroscopy using thermal emission from the trace constituents to be studied. Although neither of the two IR varieties is yet applicable in automated routine observation these techniques have considerable potential as well. For instance thermal emission spcetroscopy would also allow observations at night. Moreover, novel techniques for remote sensing of volcanic emissions, the SO2-Camera and imaging-DOAS (I-DOAS), where the I-DOAS technique trace gas distributions using the DOAS principle, came into widespread use recently. In particular the SO2 camera allows real time observation of the 2-dimensional evolution of volcanic plumes. Here we present a brief technical description and a critical assessment of the techniques listed above and discuss the relative merits of the different approaches for quantifying volcanic emissions by giving examples of successful applications in the field. Also expected future developments and requirements for volcanic surveillance are discussed.