Near Real-Time Monitoring of the Christmas 2018 Etna Eruption Using SEVIRI and Products Validation

On the morning of 24 December 2018, an eruptive event occurred at Etna, which was
followed the next day by a strong sequence of shallow earthquakes. The eruptive episode lasted until
30 December, ranging from moderate strombolian to lava fountain activity coupled with vigorous
ash/gas emissions and a lava flow e usion toward the eastern volcano flank of Valle del Bove. In
this work, the data collected from the Spinning Enhanced Visible and InfraRed Imager (SEVIRI)
instruments on board the Meteosat Second Generation (MSG) geostationary satellite are used to
characterize the Etna activity by estimating the proximal and distal eruption parameters in near real
time. The inversion of data indicates the onset of eruption on 24 December at 11:15 UTC, a maximum
Time Average Discharge Rate (TADR) of 8.3 m3/s, a cumulative lava volume emitted of 0.5 Mm3, and
a Volcanic Plume Top Height (VPTH) that reached a maximum altitude of 8 km above sea level (asl).
The volcanic cloud ash and SO2 result totally collocated, with an ash amount generally lower than SO2
except on 24 December during the climax phase. A total amount of about 100 and 35 kt of SO2 and
ash respectively was emitted during the entire eruptive period, while the SO2 fluxes reached peaks of
more than 600 kg/s, with a mean value of about 185 kg/s. The SEVIRI VPTH, ash/SO2 masses, and
flux time series have been compared with the results obtained from the ground-based visible (VIS)
cameras and FLux Automatic MEasurements (FLAME) networks, and the satellite images collected
by the MODerate resolution Imaging Spectroradiometer (MODIS) instruments on board the Terra
and Aqua- polar satellites. The analysis indicates good agreement between SEVIRI, VIS camera, and
MODIS retrievals with VPTH, ash, and SO2 estimations all within measurement errors. The SEVIRI
and FLAME SO2 flux retrievals show significant discrepancies due to the presence of volcanic ash
and a gap of data on the FLAME network. The results obtained in this study show the ability of
geostationary satellite systems to characterize eruptive events from the source to the atmosphere in
near real time during the day and night, thus o ering a powerful tool to mitigate volcanic risk on
both local population and airspace and to give insight on volcanic processes.