scholarly journals Examples of Multi-Sensor Determination of Eruptive Source Parameters of Explosive Events at Mount Etna

2021 ◽  
Vol 13 (11) ◽  
pp. 2097
Author(s):  
Valentin Freret-Lorgeril ◽  
Costanza Bonadonna ◽  
Stefano Corradini ◽  
Franck Donnadieu ◽  
Lorenzo Guerrieri ◽  
...  
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Real Time ◽  
Grain Size Distribution ◽  
Source Parameters ◽  
Radar Data ◽  
Mount Etna ◽  
Infrared Sensors ◽  
Paroxysmal Activity

Multi-sensor strategies are key to the real-time determination of eruptive source parameters (ESPs) of explosive eruptions necessary to forecast accurately both tephra dispersal and deposition. To explore the capacity of these strategies in various eruptive conditions, we analyze data acquired by two Doppler radars, ground- and satellite-based infrared sensors, one infrasound array, visible video-monitoring cameras as well as data from tephra-fallout deposits associated with a weak and a strong paroxysmal event at Mount Etna (Italy). We find that the different sensors provide complementary observations that should be critically analyzed and combined to provide comprehensive estimates of ESPs. First, all measurements of plume height agree during the strong paroxysmal activity considered, whereas some discrepancies are found for the weak paroxysm due to rapid plume and cloud dilution. Second, the event duration, key to convert the total erupted mass (TEM) in the mass eruption rate (MER) and vice versa, varies depending on the sensor used, providing information on different phases of the paroxysm (i.e., unsteady lava fountaining, lava fountain-fed tephra plume, waning phase associated with plume and cloud expansion in the atmosphere). As a result, TEM and MER derived from different sensors also correspond to the different phases of the paroxysms. Finally, satellite retrievals for grain-size can be combined with radar data to provide a first approximation of total grain-size distribution (TGSD) in near real-time. Such a TGSD shows a promising agreement with the TGSD derived from the combination of satellite data and whole deposit grain-size distribution (WDGSD).

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

2016 ◽  
Vol 9 (1) ◽  
pp. 431-450 ◽  
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.

scholarly journals Determination Of Spatial Grain Size Distribution Of A Sintered Metal

2009 ◽  
Vol 15 (2) ◽  
Author(s):  
H Amankwah ◽  
S Lauer ◽  
S Karichery ◽  
MD Ashraf-Ul-Alam
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Sintered Metal ◽  
Spatial Grain

scholarly journals Reconsideration at Field Scale of the Relationship between Hydraulic Conductivity and Porosity: The Case of a Sandy Aquifer in South Italy

2014 ◽  
Vol 2014 ◽  
pp. 1-15 ◽  
Author(s):  
Carmine Fallico
Keyword(s):  
Grain Size ◽  
Hydraulic Conductivity ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Effective Porosity ◽  
Grain Size Analysis ◽  
Size Analysis ◽  
Strict Sense ◽  
Field Scale

To describe flow or transport phenomena in porous media, relations between aquifer hydraulic conductivity and effective porosity can prove useful, avoiding the need to perform expensive and time consuming measurements. The practical applications generally require the determination of this parameter at field scale, while most of the empirical and semiempirical formulas, based on grain size analysis and allowing determination of the hydraulic conductivity from the porosity, are related to the laboratory scale and thus are not representative of the aquifer volumes to which one refers. Therefore, following the grain size distribution methodology, a new experimental relation between hydraulic conductivity and effective porosity, representative of aquifer volumes at field scale, is given for a confined aquifer. The experimental values used to determine this law were obtained for both parameters using only field measurements methods. The experimental results found, also if in the strict sense valid only for the investigated aquifer, can give useful suggestions for other alluvial aquifers with analogous characteristics of grain-size distribution. Limited to the investigated range, a useful comparison with the best known empirical formulas based on grain size analysis was carried out. The experimental data allowed also investigation of the existence of a scaling behaviour for both parameters considered.

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