Volcanic Ash Resuspension in Patagonia: Numerical Simulations and Observations

Leonardo Mingari,Lucia Dominguez,Arnau Folch,Costanza Bonadonna

doi:10.3390/atmos11090977

Abstract

Resuspension of pyroclastic deposits occurs under specific atmospheric and environmental conditions and typically prolongs and exacerbates the impact associated with the primary emplacement of tephra fallout and pyroclastic density current deposits. An accurate forecasting of the phenomenon, to support Volcanic Ash Advisory Centers (VAACs) and civil aviation management, depends on adapting volcanic ash transport and dispersion models to include specific ash emission schemes. Few studies have attempted to model the mechanisms of emission and transport of windblown volcanic ash, and a systematic study of observed cases has not been carried out yet. This manuscript combines numerical simulations along with a variety of observational data to examine the general features of ash resuspension events in northern Patagonia following the 2011 Cordón Caulle eruption (Chile). The associated outcomes provide new insights into the spatial distribution of sources, frequency of events, transport patterns, seasonal and diurnal variability, and spatio-temporal distribution of airborne ash. A novel modelling approach based on the coupling between Advanced Research core of the Weather Research and Forecasting (WRF-ARW) and FALL3D models is presented, with various model improvements that allow overcoming some limitations in previous ash resuspension studies. Outcomes show the importance of integrating source information based on field measurements (e.g., deposit grain size distribution and particle density). We provide evidence of a strong diurnal and seasonal variability associated with the ash resuspension activity in Patagonia. According to the modelled emission fluxes, ash resuspension activity was found to be significantly more intense during daytime hours. Satellite observations and numerical simulations strongly suggest that major emission sources of resuspended ash were distributed across distal areas (>100 km from the vent) of the Patagonian steppe, covered by a thin layer of fine ash. The importance of realistic soil moisture data to properly model the spatial distribution of emission sources is also highlighted.

Highlights

Major explosive volcanic eruptions can inject large amounts of particles and volcanic gases into the atmosphere, resulting in wide areas of the landscape covered by tephra-fallout deposits
Diurnal and seasonal variability of ash resuspension activity are discussed in Section 4.1 using the frequency of ash-in-suspension events observed at Bariloche
Results of WRF-ARW simulations for October 2011 are presented in Section 4.2 and timeseries of relevant variables are compared to hourly reports issued by the Bariloche weather station

Summary

Introduction

Major explosive volcanic eruptions can inject large amounts of particles and volcanic gases into the atmosphere, resulting in wide areas of the landscape covered by tephra-fallout deposits. Loose particles from fresh deposits can be remobilised by wind. The recurrence of these events represents a collateral hazard derived from the primary volcanic activity, with long-term impacts on health, environment and agriculture. The 2011 Cordón Caulle and 2015 Calbuco explosive eruptions, along with the remobilisation of the resulting fallout deposits, caused severe impacts on environment and disruptions on human activities, which prolonged for several months over dry regions of northern Patagonia [5,12,29]. The approximate locations of the major sources of resuspended ash in this region are indicated in Figure 1 (red arrows) with the key volcanoes (red triangles) involved

Methods

Results

Discussion

Conclusion