Airspace Contamination by Volcanic Ash from Sequences of Etna Paroxysms: Coupling the WRF-Chem Dispersion Model with Near-Source L-Band Radar Observations

• Published in: Remote sensing (Basel, Switzerland) Switzerland), 2023-08, Vol.15 (15), p.3760
• Main Authors: Rizza, Umberto, Donnadieu, Franck, Morichetti, Mauro, Avolio, Elenio, Castorina, Giuseppe, Semprebello, Agostino, Magazu, Salvatore, Passerini, Giorgio, Mancinelli, Enrico, Biensan, Clothilde
• Format: Article
• Language: English
• Subjects: Aerosols; Air quality; Aircraft; Airports; Airspace; Analysis; Aviation; aviation hazards; Clouds; Communication; Contamination; Diameters; Dispersion; Doppler radar; Earth Sciences; Emissions; Eruptions; Flight; France; Ground stations; Health hazards; Low pressure; Meteorology; Mount Etna; Numerical weather forecasting; Observatories; Outdoor air quality; Particulate matter; Plumes; Radar; Radar measurement; Radar meteorology; Risk management; Sciences of the Universe; Troposphere; Volcanic activity; Volcanic ash; volcanic ash cloud; Volcanic eruptions; Volcanoes; Volcanology; VOLDORAD-2B Doppler radar; Weather; WRF-Chem model
• ISSN: 2072-4292; 2072-4292
• DOI: 10.3390/rs15153760

Volcanic emissions (ash, gas, aerosols) dispersed in the atmosphere during explosive eruptions generate hazards affecting aviation, human health, air quality, and the environment. We document for the first time the contamination of airspace by very fine volcanic ash due to sequences of transient ash plumes from Mount Etna. The atmospheric dispersal of sub-10 μm (PM10) ash is modelled using the WRF-Chem model, coupled online with meteorology and aerosols and offline with mass eruption rates (MERs) derived from near-vent Doppler radar measurements and inferred plume altitudes. We analyze two sequences of paroxysms with widely varied volcanological conditions and contrasted meteorological synoptic patterns in October–December 2013 and on 3–5 December 2015. We analyze the PM10 ash dispersal simulation maps in terms of time-averaged columnar ash density, concentration at specified flight levels averaged over the entire sequence interval, and daily average concentration during selected paroxysm days at these flight levels. The very fine ash from such eruption sequences is shown to easily contaminate the airspace around the volcano within a radius of about 1000 km in a matter of a few days. Synoptic patterns with relatively weak tropospheric currents lead to the accumulation of PM10 ash at a regional scale all around Etna. In this context, closely interspersed paroxysms tend to accumulate very fine ash more diffusively at a lower troposphere and in stretched ash clouds higher up in the troposphere. Low-pressure, high-winds weather systems tend to stretch ash clouds into ~100 km wide clouds, forming large-scale vortices 800–1600 km in diameter. Daily average PM10 ash concentrations commonly exceed the aviation hazard threshold, up to 1000 km downwind from the volcano and up to the upper troposphere for intense paroxysms. Vertical distributions show ash cloud thicknesses in the range 0.7–3 km, and PM10 sometimes stagnates at ground level, which represent a potential health hazard.