The EtnaPlumeLab (EPL) research cluster: advance the understanding of Mt. Etna plume, from source characterisation to downwind impacts ANNALS OF GEOPHYSICS, Fast Track 6, 2017; doi:10.4401/ag-7106 The EtnaPlumeLab (EPL) research cluster: advance the understanding of Mt. Etna plume, from source characterisation to downwind impacts. Pasquale Sellitto1, Giuseppe Salerno 2, Pierre Briole3∗ 1 Laboratoire de Météorologie Dynamique (LMD), CNRS-UMR8539, Institut Pierre Simon Laplace, École Normale Supérieure, École Polytechnique, Université Pierre et Marie Curie, Paris, France psellitto@lmd.ens.fr 2 Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Etneo, Catania, Italy 3 Laboratoire de Géologie, CNRS-UMR8538, École Normale Supérieure, Paris, France Abstract In 2013, a multidisciplinary research cluster named EtnaPlumeLab (EPL) was established, gathering experts from volcanology and atmospheric science communities. Target of EPL is to advance the under- standing of Mt. Etna’s gas and aerosol emissions and the related processes, from source to its regional climatic impact in the Mediterranean area. Here, we present the cluster and its three interacting modules: EPL-RADIO (Radioactive Aerosols and other source parameters for better atmospheric Dispersion and Impact estimatiOns), SMED (Sulfur MEditerranean Dispersion) and Med-SuV (MEDiterranean SUper- site Volcanoes) Work Package 5. First results have provided pioneering highlights on the relevance of Mt. Etna’s plume impact at the Mediterranean regional scale. These results underline that further efforts need to be made to get insight into a synoptic volcanogenic-atmospheric chemistry/climatic understanding of volcanic plumes impact. I. Introduction M ount Etna is a persistent source of gas and aerosols in the lower and up- per Mediterranean troposphere. Its sulphur emission has been estimated to be about 10 times larger than anthropogenic emis- sions in the same area [Graf et al., 1997]. Re- cently, it has been shown that Mt. Etna has the potential to modulate the downwind aerosol properties, e.g. by the production of highly- reflective secondary sulphate aerosols from the conversion of sulphur dioxide emission [Villani et al., 2006, Sellitto et al., 2016]. In its turn, this has revealed the potential to exert a significant direct regional climatic forcing, de- pending on the environmental conditions and the optical properties of the produced aerosols [Sellitto and Briole, 2015, Sellitto et al., 2016]. Though Mt. Etna is one of the most studied volcanoes in the world, e.g. [Bonaccorso et al., 2004], its atmospheric im- pact, from small-range air quality perturba- tion to far-range climatic forcing is not yet well understood, or even, its influence might be potentially underestimated. This is due ∗This work has been partially supported by the European Union’s Horizon 2020 research and innovation programme under grant agreement No 654182 (ENVRI+), the European Union’s 7th Framework Program under the grant No 308665 (Med-SuV) and the INGV under the grant SMED. 1 mailto:psellitto@lmd.ens.fr ANNALS OF GEOPHYSICS, Fast Track 6, 2017; doi:10.4401/ag-7106 to the multidisciplinary ancestry of this argu- ment, which require a synoptic investigation framework from inner-volcanology to atmo- spheric sciences and climatology. This inte- grated framework would allow to better char- acterise the volcanic degassing and to refine and tune the atmospheric chemistry/physics and climate sciences modelling, to better un- derstand both tropospheric and stratospheric downwind impacts. Based on this undeni- able objects, in 2013 a multidisciplinary re- search cluster named EtnaPlumeLab (EPL) was kicked-off. This cluster results from the com- bination of three different interacting projects. Here, we will detail the scopes, rationale and perspectives of EPL. The paper is structured as follows: Sect. II reports the general structure of EPL, in Sect. III the three different modules that constitute the EPL cluster are detailed and finally in Sect. IV conclusions and perspectives are given. II. A multidisciplinary and multiscale modular approach for the characterisation of volcanic plumes The EPL research cluster aims at a better un- derstanding of Mount Etna’s gas and partic- ulate emissions, their generation, evolution and impacts. The target area is the Mediter- ranean basin. The cluster arises from the in- teracting combination of three different mod- ules/projects: • EPL-RADIO (Radioactive Aerosols and other source parameters for better atmo- spheric Dispersion and Impact estima- tiOns); • SMED (Sulfur MEditerranean Disper- sion); • Med-SuV (MEDiterranean SUpersite Vol- canoes) WP (work package) 5. Figure 1 shows the spatial extent and the volcanic and atmospheric processes tackled by the three EPL modules, as well as their inter- actions. The EPL-RADIO project is specifically devoted to source characterisation, in terms of geochemistry and degassing processes, and the near-source plume characterisation. The SMED project investigates the dispersion of the SO2 emissions in the Central Mediterranean region, whereas the Med-SUV WP5 project, though its multipack volcanology scope, also promotes the study of the impact of Mt. Etna’s emissions at a broader regional scale. The SMED and the Med-SuV WP5 projects superpose to a certain geographical extent. 2 ANNALS OF GEOPHYSICS, Fast Track 6, 2017; doi:10.4401/ag-7106 TroposphereTroposphere StratosphereStratosphere SO 2 ash Sicily Sicily Mediterranean Mediterranean z EPL-RADIO Geochemistry Degassing Near-source plume SO 2 → Sulfate aerosols Med-SuV WP5 Regional radiative forcing SMED Dispersion Cloud- aerosol interactions Figure 1: Spatial extents and interactions of the three modules establishing the EPL reserch cluster. Figure 2 shows the structure of the EPL research cluster into the three modules. The modules are interacting and knowledge gath- ered from one module (at smaller spatial scale) is fed to the following module (at larger spa- tial scale). For instance, EPL-RADIO has the potential to provide input source parameters for the dispersion modelling tackled by SMED; on the other hand SMED has the potential to give plume’s parameters such as to define op- tical downwind aerosols properties essential for the climatic impact estimation explored by Med-SuV WP5. The different scientific tar- gets and the methods employed in each of the three modules (e.g., modelling and observa- tions) are also indicated and color-coded. The timeframes of the modules are also shown. The broad split into (a) source - EPL-RADIO , (b) evolution - SMED, and (c) impact - Med-SuV WP5, of Mt. Etna emissions follows from Fig. 1. The EPL research cluster relies on high qual- ity direct and remote ground- and satellite- based observations of volcanic plume, together with chemistry, transport and radiative trans- fer modelling. While for the SMED and Med- SuV the employ of both observations and mod- elling is needed, EPL-RADIO is only based on ground- and satellite-based measurements for characterising the aerosol source (including gaseous precursors of secondary aerosols). The Med-SuV project ended in December 2015, but results are still available for further investiga- tion. The SMED project runs from November 2015 to end 2016. The EPL-RADIO activities are foreseen until summer 2017. 3 ANNALS OF GEOPHYSICS, Fast Track 6, 2017; doi:10.4401/ag-7106 Emission rates of primary aerosols and and of secondary aerosols precursors Aerosol near-source properties Source Impact Regional distribution of primary aerosols, secondary aerosol and their precursors Plume dispersion Chemical and micro-physical evolution Evolution Downwind aerosol properties perturbations Direct Radiative forcing = Chemistry/transport modelling = Radiative transfer modelling = Satellite measurements = Ground-based measurements 2013 2014 2015 20162015 2017 2018 Med-SuV WP5Med-SuV WP5 SMEDSMED EPL-RADIOEPL-RADIO EP L- RA DI O EP L- RA DI O SM ED SM ED Me d- SU V Me d- SU V W P5W P5 Cloud-aerosols interactions Air quality Figure 2: Breakdown of the EPL research cluster, with indication of scientific targets, methods and timeframes of the three individual modules of the cluster. III. The different modules III.1 EPL-RADIO The EPL-RADIO project aims at improving the characterisation of Mt. Etna as atmospheric aerosols source, gathering multi-domain (solid Earth and atmospheric sciences) information [Sellitto, 2016]. Object of EPL-Radio is to ad- vance our knowledge on Mt. Etna’s emis- sions, targeting emission processes, from inner degassing mechanisms to aerosol near-source characterisation. This project brings together different and original information, such as observations of (a) radioactive disequilibria of radon daugh- ters, (b) coupled direct/remote size-resolved aerosols distribution, (c) primary/secondary near-source sulfate aerosols partitioning. This volcanic aerosols decription allows a detailed size-resolved physicochemical characterisation of the emitted aerosols. The point (a) is more thoroughly discussed by Terray et al. (2016). The volcanic aerosol source is characterised by determining the size-resolved aerosol emissions, with a cascade impactor and a Microtops-II optical spectrometers (see, e.g. [Mather et al., 2004]), and the primary frac- tion of the emitted sulfate aerosols (with re- spect to the secondary sulfate aerosols pro- duced by in-plume conversion of SO2 emis- sions) by FTIR (Fourier Transform Infrared) spectroscopy [La Spina et al., 2010]. Comple- mentary three-dimensional aerosols informa- tion is obtained with a scanning AMPLE Li- 4 ANNALS OF GEOPHYSICS, Fast Track 6, 2017; doi:10.4401/ag-7106 DAR (Aerosol Multi-wavelength Polarization Lidar Experiment - Light Detection And Rang- ing) system [Scollo et al., 2015]. These param- eters are crucial to assess the size-dependent plume dispersion and downwind climatic im- pacts, and are then an input knowledge for the SMED and Med-SuV WP5 modules. The EPL-RADIO project is linked to an ex- tended transnational access at Mt. Etna’s sum- mit craters area, partially funded by the Euro- pean Union’s Horizon 2020 research and inno- vation programme (ENVRI+ TNA). Two dedi- cated campaigns have been scheduled in 2016 (C1: aerosol sampling at the summit craters, C2: distal observations in an area of about 30 km from the craters) and 2 in 2017 (C3 and C4). Highest priority is given to C1 and C3, i.e. the field experiments at the summit craters. First, preliminary results of campaigns C1 and C2 have shown how near-source processes (in the first few km downwind the emitting craters) play a major role in determining the volcanic aerosol properties downwind, thus influencing the dispersion and impacts of the plume. III.2 SMED The SMED project [Salerno et al., 2016] aims at assessing: (a) the spatial distribution of the re- gional atmospheric dispersion of Mt. Etna’s volcanic emissions, (b) the impact of moder- ate volcanic activity and long-lived passive de- gassing, and (c) lower to upper tropospheric sulphate aerosol formation processes and life- cycle, in the regional area of Central-Eastern sector of the Mediterranean basin. While the project is mostly target to the Central-Eastern Mediterranean, where up to 80% of the Etnean plume dis- perses [Sellitto et al., 2017], the less downwind- ventilated Central-Southern Mediterranean re- gion is also explored [Sellitto et al., 2016]. The study is pursued by a comprehen- sive set of remote ground- and satellite-based measurements, such as: (a) the INGV - Os- servatorio Etneo FLAME (FLux Automatic MEasurements) ultraviolet scanning spectrom- eter network [Salerno et al., 2009] and FTIR [La Spina et al., 2010] measurements, (b) low Earth orbit (MODIS - MODerate resolution Imaging Spectroradiometer, IASI - Infrared At- mospheric Sounding Interferometer) and geo- stationary (SEVIRI - Spinning Enhanced Vis- ible and InfraRed Imager) satellite sensors, (c) the AERONET (AErosol RObotic NET- work - http://aeronet.gsfc.nasa.gov) stations in Nicolosi(Catania), Italy, and in the Central- Eastern Mediterranean, (d) the ENEA super- station for climate observation in Lampedusa. The AERONET stations routinely measure col- umn optical and microphysical properties of the aerosol layer, which are used to assess the downwind impact of Mt. Etna’s sulphur emis- sions. Additionally, the Lampedusa station is equipped with complementary instrumenta- tion, including a LiDAR which provides height resolved aerosol and clouds information. These data allow the characterization of aerosol layer and their precursors, which is fundamental for identifying downwind volcanic contribu- tion. Ground and space observations are com- plemented with an atmospheric Lagrangian model (FLEXPART - FLEXible PARTicle disper- sion model, https://flexpart.eu/) for inspect- ing the transport and dispersion of volcanic plumes over the Mediterranean region. First results have allowed the character- ization of the Etnean plumes dispersion at the decadal timescale, thus quantifying the frequency of ventilation of different mediter- ranean sub-sectors and confirming the preva- lence (about 80% frequency) of the dispersion of the plumes towards the eastern quadrant (i.e., towards Greece) [Sellitto et al., 2017]. III.3 Med-SuV WP5 The European Union’s 7th Framework Pro- gram Med-SuV project aims at improving the assessment capacity of volcanic hazards in se- lected supersites (i.e., well instrumented sites) of Southern Italy. The main targets of this project are the optimisation and integration of existing and new observation/monitoring systems, the systematic study of volcanic pro- 5 ANNALS OF GEOPHYSICS, Fast Track 6, 2017; doi:10.4401/ag-7106 cesses and the enhancement of the coordina- tion between the scientific and end-user com- munities. Work package (WP) 5 of Med-SuV is de- voted to improve the knowledge of processes occurring at Mt. Etna supersite. The primary aim of Med-SuV WP5 is the study of inner volcanology processes. Nevertheless, the de- gassing, transport and atmospheric impacts of Mt. Etna are also addressed. One specific tar- get of Med-SuV WP5 is to extend the scopes of the Vamos Seguro (Volcanic Ash Monitor- ing and fOrecaSting between Sicilia and malta arEa and sharinG of the resUlts foR aviatiOn safety) project (http://www.vamosseguro.eu/) and to study the downwind impacts of Mount Etna’s ash and SO2 emissions in the central Mediterranean. In such a sense, Med-SuV WP5 extends geographically the scopes of SMED (see Fig. 1), allowing to investigate the regional impacts of volcanic emissions in the Central Mediterranean. These interacting studies have shown, for the first time, that even relatively weak erup- tions have the potential to modulate the optical and micro-physical properties of the aerosol layer at hundreds of km from Mt. Etna, thus exerting a significant, episodic radiative forcing [Sellitto et al., 2016], which is critically depen- dent from chemical/micro-physical processes in atmosphere [Sellitto and Briole, 2015]. The radiative impact is studied with both radiative transfer modelling and satellite observations of radiative fluxes. Longer-term analyses have shown that Mt. Etna’s sulphur emissions can have a significant decadal impact on aerosol op- tical properties even in weakly ventilated sub- sectors, like observed at Lampedusa (south- western quadrant) [Sellitto et al., 2017]. IV. Conclusion and Perspectives Emissions of volcanic gases and particles pro- foundly impact on terrestrial environment, at- mospheric composition and climate, at various temporal and spatial scales. Early research results suggested that the regional impact of Mt. Etna in the Mediterranean might be poten- tially underestimated. A novel and vigorous multidisciplinary approach is then required to explore this subject. Hence, in 2013, the EPL multidisciplinary and multiscale research clus- ter has been established, aiming at a better characterisation of Mt. Etna’s emissions, from source to downwind impacts. First results have shown pioneering evi- dences of Mt. Etna’s impacts in the Mediter- ranean, in terms of the modulation of the aerosol optical properties and of the potential direct radiative forcing at selected locations. The near-craters and near-source distal EPL- RADIO campaigns, foreseen for the summers 2016 and 2017, will provide further insights into the degassing and emission processes, and near-source plume characterisation. This will allow to refine the regional dispersion mod- elling and help the interpretation of satellite data at the regional scale. On the other hand, the SMED activities will provide an overall pic- ture of the dispersion and regional distribution of volcanic effluents in the Mediterranean, that will give better direct climatic forcing estima- tions. Further important topics, not addressed at present by EPL are the modelling and observa- tion of the chemical and micro-physical evolu- tion of the plume, the role of volcanic aerosol in the formation, determination of optical proper- ties and climatic forcing of low and high clouds and, at a smaller spatial scale, the impact of volcanic emissions on local and regional air quality (see Fig. 2). Further research is on- going to include these aspects in the research cluster. Acknowledgements All participants of the EPL-RADIO, SMED and MedSuV WP5 projets are gratefully acknowl- edged, especially: T. Caltabiano, E. Carboni, S. Corradini, A. di Sarra, P.-J. Gauthier, A. La Spina, B. Legras, L. Merucci, G. Puglisi, S. Scollo, L. Terray. 6 ANNALS OF GEOPHYSICS, Fast Track 6, 2017; doi:10.4401/ag-7106 References [Bonaccorso et al., 2004] Bonaccorso, A. et al. (2004). Mt. Etna: Volcano Labora- tory. American Geophysical Union publisher, Washington, DC, 143. [Graf et al., 1997] Graf, H. 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The impact of Mount Etna sulfur emis- sions on the atmospheric composition and aerosol properties in the central Mediter- ranean: a statistical analysis over the pe- riod 2000-2013 based on observations and Lagrangian modelling Atmos. Environ.,148, 77–88. [Terray et al., 2016] Terray, L. et al. (2016). De- gassing dynamics at Mount Etna inferred from radioactive disequilibria (210Pb- 210Bi-210Po) in the volcanic plume. Geo- phys. Res. Abstr., 18, EGU2016-10373-3. [Villani et al., 2006] Villani, M. G. et al. (2006). Transport of volcanic aerosol in the tropo- sphere: The case study of the 2002 Etna plume. J. Geophys. Res., 111, D21102. 7 Introduction A multidisciplinary and multiscale modular approach for the characterisation of volcanic plumes The different modules EPL-RADIO SMED Med-SuV WP5 Conclusion and Perspectives