Applications of Ground-Based Infrared Cameras for Remote Sensing of Volcanic Plumes

Ground-based infrared cameras can be used effectively and safely to provide quantitative information about small to moderate-sized volcanic eruptions. This study describes an infrared camera that has been used to measure emissions from Mt Etna and Stromboli (Sicily, Italy) volcanoes. The camera provides calibrated brightness temperature images in a broadband (8--14 µm) channel that is used to determine height, plume ascent rate and volcanic cloud/plume temperature and emissivity at temporal sampling rates of up to 1 Hz. The camera can be operated in the field using a portable battery and includes a microprocessor, data-storage and WiFi. The processing and analyses of the data are described with examples from the field experiments. The updraft speeds of the small eruptions at Stromboli are found to decay with a timescale of $\sim$10 min and the volcanic plumes reach thermal equilibrium within $\sim$2 min. A strong eruption of Mt Etna on 1 April 2021 was found to reach $\sim$9 km, with ascent speeds of 10--20 ms$^{-1}$. The plume, mostly composed of water vapour and SO$_2$ gas became bent over by the prevailing winds at high levels.