First results of the Piton de la Fournaise STRAP 2015 experiment: multidisciplinary tracking of a volcanic gas and aerosol plume

Abstract

<p><strong>Abstract.</strong> The STRAP (Synergie Transdisciplinaire pour Répondre aux Aléas liés aux Panaches volcaniques) campaign was conducted in 2015 to investigate the volcanic plumes of Piton de La Fournaise (La Réunion, France). For the first time, measurements at the local (near the vent) and at the regional scales around the island were conducted. The STRAP 2015 campaign has become possible thanks to a strong cross-disciplinary collaboration between volcanologists and meteorologists. The main observations during four eruptive periods (85 days) are summarized. They include the estimates of SO<sub>2</sub>, CO<sub>2</sub> and H<sub>2</sub>O emissions, the altitude of the plume at the vent and over different areas of La Réunion Island, the evolution of the SO<sub>2</sub> concentration, the aerosol size distribution, and the aerosol extinction profile. A climatology of the volcanic plume dispersion is also reported. Simulations and measurements showed that the plume formed by weak eruption has a stronger interaction with the surface of the island. Strong SO<sub>2</sub> and particles concentrations above 1000 ppb and 50 000 cm<sup>−3</sup>, respectively, are frequently measured over 20 km of distance from the Piton de la Fournaise. The measured aerosol size distribution shows the predominance of small particles in the volcanic plume. A particular emphasis is placed on the gas-particle conversion with several cases of strong nucleation of sulfuric acid observed within the plume and at the distal site of the Maïdo observatory. The STRAP 2015 campaign gave a unique set of multi-disciplinary data that can now be used by modellers to improve the numerical paramameterizations of the physical and chemical evolution of the volcanic plumes.</p>

Volcanic Plume Aging During Passive Degassing and Low Eruptive Events of Etna and Stromboli Volcanoes

“…In order to understand the processes involved in the atmospheric volcanic emission rates and in the composition of the gas and particles mixture erupted from the vent, two STRAP campaigns were conducted (the acronym STRAP means “Synergie Transdisciplinaire pour répondre aux Aléas liés aux Panaches volcaniques” in french and can be translated in english to “Transdisciplinary collaboration to investigate volcano plumes risks”). One of them was made around Piton de la Fournaise, in La Réunion (Tulet et al, ) and another around Etna and Stromboli volcanoes, in Italy (Sahyoun et al, ; this study).…”

The isotopic composition of near‐surface water vapor at the Maïdo observatory (Reunion Island, southwestern Indian Ocean) documents the controls of the humidity of the subtropical troposphere

“…As a result, during the day, air masses from the marine boundary layer are transported by upslope winds along the west coast toward the MO [ Lesouëf et al ., ]. When the daytime sea breeze weakens on the west coast, moist air masses can also originate from the nearby Cirque de Mafate (caldera east of Maïdo in Figure ) or being advected from the windward (eastern) side of the island to Maïdo site by strong southeasterly trade winds [ Lesouëf , ; Lesouëf et al ., , ; Tulet et al ., ]. During the night, the transport pattern is reversed as trade wind flow is pushed offshore by divergence of cooled air from the land [ Baray et al ., ].…”

Evidence of New Particle Formation Within Etna and Stromboli Volcanic Plumes and Its Parameterization From Airborne In Situ Measurements

“…This process is called new particle formation (NPF), where clusters are formed from the gaseous phase as a first step and, later on, grow to larger sizes (>100 nm) at which they can act as CCN (Hobbs et al, ; Mather et al, ) or ice nuclei (Hoyle et al, ) and impact the climate (Kerminen et al, ; Kulmala et al, , , ; Kulmala & Kerminen, ; Kulmala & Laaksonen, ; Makkonen et al, ). During active eruptions, both primary and secondary particles are present in different atmospheric vertical layers (Ilyinskaya et al, ; Mather & Pyle, ; Tulet et al, ). Conversely, during passive emissions, primary aerosols, with low concentrations, are often limited to the remobilization of accidental lithic (derived from the conduit and crater walls), while emissions of gaseous species may remain significant, likely to contribute to the formation of new particles.…”

“…While a large number of studies have investigated volcanic emissions through in situ ground‐based and satellite/radar measurements (Carn et al, ; Galle et al, ; Kantzas & McGonigle, ; Mather, ; McCormick et al, ; McGonigle et al, ; McGonigle & Oppenheimer, ), airborne in situ measurements of volcanic emissions remain very scarce (Mauldin et al, ; Oppenheimer et al, ; Petäjä et al, ; Radke, ; Rose et al, ; Tulet et al, ; Vignelles et al, ; Weber et al, ). The limited number of volcanic plume airborne observations investigating NPF arises from challenges associated with restricted timescales and the impact of temporal and spatial plume's heterogeneities under typically harsh environments, besides the costly deployment of highly sophisticated instrumentation aboard an aircraft in such harsh conditions (Delmelle, ; Mauldin et al, ; Oppenheimer et al, ).…”