Mass discharge rate retrieval combining weather radar and thermal camera observations

Abstract

The mass discharge rate is a key parameter for initializing volcanic ash dispersal models. Commonly used empirical approaches derive the discharge rate by the plume height as estimated by remote sensors. A novel approach based on the combination of weather radar observations and thermal camera imagery is presented here. It is based on radar ash concentration estimation and the retrieval of the vertical exit velocities of the explosive cloud using thermal camera measurements. The applied radar retrieval methodology is taken from a revision of previously presented work. Based on the analysis of four eruption events of the Mount Etna volcano (Sicily, Italy) that occurred in December 2015, the proposed methodology is tested using observations collected by three radar systems (at C and X band) operated by the Italian Department of Civil Protection. The total erupted mass was estimated to be about 9·109 kg and 2.4·109 kg for the first and second events, respectively, while it was about 1.2·109 kg for both the last two episodes. The comparison with empirical approaches based on radar‐retrieved plume height shows a reasonably good agreement. Additionally, the comparative analysis of the polarimetric radar measurements provides interesting information on the vertical structure of the ash plume, including the size of the eruption column and the height of the gas thrust region.

Paroxysmal Explosions, Lava Fountains and Ash Plumes at Etna Volcano: Eruptive Processes and Hazard Implications

“…Explosive activity from this crater increased in intensity and became almost regular since 27 October, climaxing with a sequence of four paroxysmal events between 3 and 5 December (Vulpiani et al, 2016;Bonaccorso and Calvari, 2017;Neri et al, 2017). The four explosive events interrupted the usual trend of inflation observed at Mt.…”

“…They were characterized by decreasing LF maximum heights (from 4.1 to 1.1 km), by lack of associated lava flows, by durations varying between 65 and 114 min, and by a total erupted volume of at least 10 × 10 6 m 3 dense rock equivalent (Bonaccorso and Calvari, 2017). The eruption columns and ash plume rose vertically with velocities between 150 and 200 m s −1 , and the transition from the convective to the umbrella region was observed at ∼8 km height (Vulpiani et al, 2016). In about 10 min the ash plume expanded up to 10-15 km above sea level (a.s.l.…”

“…In about 10 min the ash plume expanded up to 10-15 km above sea level (a.s.l. ; Vulpiani et al, 2016;Corsaro et al, 2017). Tephra fallout accumulated mostly within the summit crater, resulting in a fountain-fed rheomorphic lava of ∼7.2 × 10 6 m 3 (Corsaro et al, 2017;Neri et al, 2017).…”

From magma ascent to ash generation: investigating volcanic conduit processes by integrating experiments, numerical modeling, and observations

“…Parameters as plume exit velocity and trajectory, mass discharge rates, gas fluxes, gas compositions, and grain size distributions can now be measured in real time using high-speed visual, thermal, infrared and sulfur dioxide cameras [Bani et al 2013, Harris 2013, Bombrum et al 2014, Gaudin et al 2014a, b, Valade et al 2014, Barni et al 2015, Bombrum et al 2015, Cerminara et al 2015, Bombrun et al 2016, Gaudin et al 2016], a combination of thermal camera, weather radar observations and/ or infrasound measurements , De Angelis et al 2016, Vulpiani et al 2016, and open-path Fourier transform infrared (OP-FTIR) spectrometry [La Spina et al 2015, Allard et al 2016. These measurements have highlighted the unsteady nature of these parameters.…”

The iron-catalysed surface reactivity and health-pertinent physical characteristics of explosive volcanic ash from Mt. Etna, Italy

“…Between 3 and 5 December 2015, four high-energy, lava-fountaining episodes took placed at the Voragine crater, producing eruption plumes up to 15 km a.s.l. (Vulpiani et al 2016) and dispersing fine tephra up to hundreds of km away from the vent (Corsaro et al 2017). …”