Reconstructing volcanic plume evolution integrating satellite and ground-based data: Application to the 23rd November 2013 Etna eruption

Abstract. Recent explosive eruptions recorded from different volcanoes worldwide (e.g. Hekla in 2000, Eyjafjallajökull in 2010, Cordón-Caulle in 2011) demonstrated the necessity of a better assessment of the eruption source parameters (e.g. column height, mass eruption rate and especially the Total Grain-Size Distribution – TGSD) to reduce the uncertainties associated with the far-travelling airborne ash mass. To do so, volcanological studies started to integrate observations in order to use more realistic numerical inputs, crucial for taking robust volcanic risk mitigation actions. On 23rd November 2013, Etna volcano (Italy) erupted producing a 10-km height plume, from which two volcanic clouds were observed at two different altitudes from satellite (MSG-SEVIRI, MODIS). One was described as mainly composed by very fine ash (i.e. PM20), whereas the second one as made of ice/SO2 droplets (i.e. not measurable in terms of ash mass). Atypical north-easterly winds transported the tephra from Etna towards the Puglia region (southern Italy), permitting tephra sampling in proximal (i.e. ~ 5–25–km from source) and medial areas (i.e. Calabria region, ~ 160 km). Based on the field data analysis, we estimated the TGSD but the paucity of data (especially related to the fine ash fraction) prevented it from being entirely representative of the initial magma fragmentation. To better estimate the TGSD covering the entire grain-size spectrum, we integrated the available field data with X-band weather radar and satellite retrievals. The resulting TGSD is used as input for the FALL3D tephra dispersal numerical model to reconstruct the tephra loading and the far-travelling airborne ash mass. The optimal TGSD is selected by solving an inverse problem through a best-fit with the field, ground-based and satellite-based measurements. The results suggest a total erupted mass of 1.2 × 109 kg, which is very similar to the field-derived value of 1.3 × 109 kg, and a TGSD with a PM20 fraction between 3.6 and 9.0 wt%.

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FPLUME-1.0: An integral volcanic plume model accounting for ash aggregation

Geoscientific Model Development ◽

10.5194/gmd-9-431-2016 ◽

2016 ◽

Vol 9 (1) ◽

pp. 431-450 ◽

Cited By ~ 35

Author(s):

A. Folch ◽

A. Costa ◽

G. Macedonio

Keyword(s):

Grain Size ◽

Size Distribution ◽

Grain Size Distribution ◽

Risk Mitigation ◽

Source Parameters ◽

Air Entrainment ◽

Phase Changes ◽

Column Height ◽

Volcanic Plume ◽

Eruption Column

Abstract. Eruption source parameters (ESP) characterizing volcanic eruption plumes are crucial inputs for atmospheric tephra dispersal models, used for hazard assessment and risk mitigation. We present FPLUME-1.0, a steady-state 1-D (one-dimensional) cross-section-averaged eruption column model based on the buoyant plume theory (BPT). The model accounts for plume bending by wind, entrainment of ambient moisture, effects of water phase changes, particle fallout and re-entrainment, a new parameterization for the air entrainment coefficients and a model for wet aggregation of ash particles in the presence of liquid water or ice. In the occurrence of wet aggregation, the model predicts an effective grain size distribution depleted in fines with respect to that erupted at the vent. Given a wind profile, the model can be used to determine the column height from the eruption mass flow rate or vice versa. The ultimate goal is to improve ash cloud dispersal forecasts by better constraining the ESP (column height, eruption rate and vertical distribution of mass) and the effective particle grain size distribution resulting from eventual wet aggregation within the plume. As test cases we apply the model to the eruptive phase-B of the 4 April 1982 El Chichón volcano eruption (México) and the 6 May 2010 Eyjafjallajökull eruption phase (Iceland). The modular structure of the code facilitates the implementation in the future code versions of more quantitative ash aggregation parameterization as further observations and experiment data will be available for better constraining ash aggregation processes.

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FPLUME-1.0: An integrated volcanic plume model accounting for ash aggregation

Geoscientific Model Development Discussions ◽

10.5194/gmdd-8-8009-2015 ◽

2015 ◽

Vol 8 (9) ◽

pp. 8009-8062 ◽

Cited By ~ 2

Author(s):

A. Folch ◽

A. Costa ◽

G. Macedonio

Keyword(s):

Grain Size ◽

Size Distribution ◽

Grain Size Distribution ◽

Risk Mitigation ◽

Source Parameters ◽

Air Entrainment ◽

Phase Changes ◽

Column Height ◽

Volcanic Plume ◽

Eruption Column

Abstract. Eruption Source Parameters (ESP) characterizing volcanic eruption plumes are crucial inputs for atmospheric tephra dispersal models, used for hazard assessment and risk mitigation. We present FPLUME-1.0, a steady-state 1-D cross-section averaged eruption column model based on the Buoyant Plume Theory (BPT). The model accounts for plume bent over by wind, entrainment of ambient moisture, effects of water phase changes, particle fallout and re-entrainment, a new parameterization for the air entrainment coefficients and a model for wet aggregation of ash particles in presence of liquid water or ice. In the occurrence of wet aggregation, the model predicts an "effective" grain size distribution depleted in fines with respect to that erupted at the vent. Given a wind profile, the model can be used to determine the column height from the eruption mass flow rate or vice-versa. The ultimate goal is to improve ash cloud dispersal forecasts by better constraining the ESP (column height, eruption rate and vertical distribution of mass) and the "effective" particle grain size distribution resulting from eventual wet aggregation within the plume. As test cases we apply the model to the eruptive phase-B of the 4 April 1982 El Chichón volcano eruption (México) and the 6 May 2010 Eyjafjallajökull eruption phase (Iceland).

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Reconstructing volcanic plume evolution integrating satellite and ground-based data: application to the 23 November 2013 Etna eruption

Atmospheric Chemistry and Physics ◽

10.5194/acp-18-4695-2018 ◽

2018 ◽

Vol 18 (7) ◽

pp. 4695-4714 ◽

Cited By ~ 14

Author(s):

Matthieu Poret ◽

Stefano Corradini ◽

Luca Merucci ◽

Antonio Costa ◽

Daniele Andronico ◽

...

Keyword(s):

Risk Mitigation ◽

Source Parameters ◽

Volcanic Eruptions ◽

Radar Data ◽

Column Height ◽

Volcanic Plume ◽

Easterly Wind ◽

Measurement Analysis ◽

Best Fitting ◽

Tephra Loading

Abstract. Recent explosive volcanic eruptions recorded worldwide (e.g. Hekla in 2000, Eyjafjallajökull in 2010, Cordón-Caulle in 2011) demonstrated the necessity for a better assessment of the eruption source parameters (ESPs; e.g. column height, mass eruption rate, eruption duration, and total grain-size distribution – TGSD) to reduce the uncertainties associated with the far-travelling airborne ash mass. Volcanological studies started to integrate observations to use more realistic numerical inputs, crucial for taking robust volcanic risk mitigation actions. On 23 November 2013, Etna (Italy) erupted, producing a 10 km height plume, from which two volcanic clouds were observed at different altitudes from satellites (SEVIRI, MODIS). One was retrieved as mainly composed of very fine ash (i.e. PM20), and the second one as made of ice/SO2 droplets (i.e. not measurable in terms of ash mass). An atypical north-easterly wind direction transported the tephra from Etna towards the Calabria and Apulia regions (southern Italy), permitting tephra sampling in proximal (i.e. ∼ 5–25 km from the source) and medial areas (i.e. the Calabria region, ∼ 160 km). A primary TGSD was derived from the field measurement analysis, but the paucity of data (especially related to the fine ash fraction) prevented it from being entirely representative of the initial magma fragmentation. To better constrain the TGSD assessment, we also estimated the distribution from the X-band weather radar data. We integrated the field and radar-derived TGSDs by inverting the relative weighting averages to best fit the tephra loading measurements. The resulting TGSD is used as input for the FALL3D tephra dispersal model to reconstruct the whole tephra loading. Furthermore, we empirically modified the integrated TGSD by enriching the PM20 classes until the numerical results were able to reproduce the airborne ash mass retrieved from satellite data. The resulting TGSD is inverted by best-fitting the field, ground-based, and satellite-based measurements. The results indicate a total erupted mass of 1.2  ×  109 kg, being similar to the field-derived value of 1.3  ×  109 kg, and an initial PM20 fraction between 3.6 and 9.0 wt %, constituting the tail of the TGSD.

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Forecasting the dispersion and fallout of volcanic ash during a crisis: Assessment of the September 20, 2020 eruption at Sangay volcano in Ecuador

10.5194/egusphere-egu21-13871 ◽

2021 ◽

Author(s):

Benjamin Bernard ◽

Pablo Samaniego ◽

Marjorie Encalada Simbaña

Keyword(s):

Grain Size ◽

High Altitude ◽

Field Data ◽

Satellite Images ◽

Source Parameters ◽

Column Height ◽

Eruption Column ◽

Eruptive Dynamics ◽

Eruptive Episode ◽

Ash Fallout

Sangay volcano (2.00&#176;S, 78.34&#176;W, 5326 m asl), located at the southern end of the Northern Volcanic Zone of the Andes (Morona Santiago province, Ecuador), has frequently been referred as one of the most active volcanoes in the world. Its most recent eruptive period began on May 7, 2019 and is still ongoing. It is characterized by a semi-continuous viscous lava flow emission accompanied by frequent low magnitude explosions (Vasconez et al., this meeting). This eruptive episode is the first in more than two decades to produce significant impacts both locally and regionally, and reached its paroxysm on September 20, 2020 without clear precursory signals. The eruption started at 9:20 (UTC) and lasted about one and a half hours. The eruptive column rapidly split into a high-altitude (15 km asl) gas-rich cloud, drifting eastward at 5-8 m/s and a lower (12 km asl) ash-rich cloud, drifting westward at 10-14 m/s. The ash began to fall at 11:00 (UTC) in the communities near the volcano and reached the city of Guayaquil, the second largest city in Ecuador, at 13:00 (UTC), forcing the closure of the international airport.In this work, we evaluate the ash dispersion simulations performed by the IG-EPN using the Ash3D model before, during and after the eruption using different eruptive source parameters (ESP), by comparison with the available satellite images (GOES-16). The simulated ash fallout for each set of ESP is compared to reports from the community and volcanic observers, as well as with a fallout map obtained from a four-days field trip initiated immediately after the eruption to ensure good quality of samples and measurements (September 20-23). Ash fallout was estimated using thickness measurements where possible and area density at 40 sites located between 30 and 180 km from the volcano. The grain size distribution of 35 samples was obtained by laser diffraction.Our results show that the general westward direction and speed of the ash cloud in the simulations is coherent with the satellite images, except for the high-altitude, gas-rich cloud. However, large discrepancies were found when comparing the simulated and measured ash fallout. Field data shows that the first simulation using ESP based on the previous activity at Sangay, underestimated the eruption size, while the second simulation using the eruption column height estimated in near-real time overestimated it. As expected, the simulation carried out immediately after the eruption, based on the first field results shows the best correlation with field data, although there are still some second-order discrepancies. In particular, the plume axis was shifted about 12&#176; northward in the simulation, which is attributed to the atmospheric model. We also noted that the deposition pattern was slightly different between the field data and the simulation. Grain size analysis reveals uni- to multimodal distributions, associated with complex eruptive dynamics and aggregation that probably influenced the sedimentation process. Further research is needed to better understand the eruptive dynamics at Sangay in order to improve forecasts.

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