Near-Real-Time Tephra Fallout Assessment at Mt. Etna, Italy

Simona Scollo,Stefano Corradini,Giuseppe Carparelli,Michele Prestifilippo,Emilio Biale,Raffaello Cioni,Eduardo Rossi,Malvina Silvestri,Costanza Bonadonna,Massimo Musacchio,Luca Merucci,Carmelo Cassisi,Wim Degruyter,Emilio Pecora

doi:10.3390/rs11242987

Abstract

During explosive eruptions, emergency responders and government agencies need to make fast decisions that should be based on an accurate forecast of tephra dispersal and assessment of the expected impact. Here, we propose a new operational tephra fallout monitoring and forecasting system based on quantitative volcanological observations and modelling. The new system runs at the Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Etneo (INGV-OE) and is able to provide a reliable hazard assessment to the National Department of Civil Protection (DPC) during explosive eruptions. The new operational system combines data from low-cost calibrated visible cameras and satellite images to estimate the variation of column height with time and model volcanic plume and fallout in near-real-time (NRT). The new system has three main objectives: (i) to determine column height in NRT using multiple sensors (calibrated cameras and satellite images); (ii) to compute isomass and isopleth maps of tephra deposits in NRT; (iii) to help the DPC to best select the eruption scenarios run daily by INGV-OE every three hours. A particular novel feature of the new system is the computation of an isopleth map, which helps to identify the region of sedimentation of large clasts (≥5 cm) that could cause injuries to tourists, hikers, guides, and scientists, as well as damage buildings in the proximity of the summit craters. The proposed system could be easily adapted to other volcano observatories worldwide.

Highlights

For each of the cameras, we proceeded as follows: (1) the camera was calibrated as described in [35] (the positions of the cameras are well-known using the Global Positioning System (GPS) location); (2) the estimation of the orientation was made using a 3D tool aimed to simulate the cameras and was by performed by aligning the skyline with the digital elevation model (DEM) of Etna volcano; (3) to estimate the plume height, we assumed that the plume had a negligible depth and that it was confined to a vertical plane that rotated according to the wind direction
Scenario Identification The scenario (WPS versus strong plume scenarios (SPS)) is identified using the scaling parameter [41], defined as Π: Π = NH 1.8 v α β where H is the maximum column height above the crater (m), v is wind speed averaged over the column height (m/s), α is the radial air entrainment coefficient, β is the wind entrainment coefficient, and N is the buoyancy frequency (s−1) averaged across the column height, which quantifies the stratification of the atmosphere
We show a new operational system implemented in the 24/7 Etna volcano surveillance that is able to model plume dispersal and fallout in NRT using volcanological observations collected in NRT

Summary

Introduction

Worldwide Operational Monitoring and Forecasting of Tephra Dispersal and Fallout. The assessment of tephra fallout and dispersal in distal areas has been largely considered [9,10,11,12], the reduction of volcanic impacts in proximal areas and within the first hour from the beginning of the eruption is still a challenge. As a matter of fact, regardless of the importance of this information for emergency responders and government agencies, the operational systems capable of monitoring tephra dispersal and fallout in near-real-time (NRT) and returning the expected impact assessment are still limited and not fully adapted to the growing requirements of precision and reliability

Methods

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Discussion

Conclusion