Publication Date:
2018-06-09
Description:
Volcanic plumes from Etna volcano (Italy) are governed by easterly winds driving ash over the Ionian Sea. The limited land tephra deposit makes total grain-size distribution (TGSD) assessment and its fine ash fraction highly uncertain. On 23 February 2013, a lava fountain produced a ~9-km-high column above sea level (a.s.l.). The atypical north-easterly wind direction dispersed the tephra from Etna to the Puglia region (southern Italy) allowing sampling up to very distal areas. This study uses field measurements to estimate the field-based TGSD. Very fine ash distribution (particle matter below 10 μm—PM10) is explored parameterizing the field-TGSD through a bi-lognormal and bi-Weibull distribution. However, none of the two latter TGSDs allow simulating any far-traveling airborne ash up to distal areas. Accounting for the airborne ash retrieved from satellite (Spinning Enhanced Visible and Infrared Imager), we proposed an empirical modification of the field-based TGSD including very fine ash through a power law decay of the distribution. The input source parameters are inverted by comparing simulations against measurements. Results suggest a column height of ~8.7 km a.s.l., a total erupted mass of ~4.9 × 109 kg, a PM10 content between 0.4 and 1.3 wt%, and an aggregate fraction of ~2 wt% of the fine ash. Aerosol optical depth measurements from the AErosol RObotic NETwork are also used to corroborate the results at ~1,700 km from the source. Integrating numerical models with field, ground-based, and satellite-based data aims at providing a better TGSD estimation including very fine ash, crucial for air traffic safety. ©2018. American Geophysical Union. All Rights Reserved.
Print ISSN:
2169-9313
Electronic ISSN:
2169-9356
Topics:
Geosciences
,
Physics
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