Title: VOlcanic pLume chAracterization using sounNDing balloOns (VOLANDO)

Scientific Person in Charge: Manuele Faccenda | Programme: PRIN 2022 DM 104/2022

Volcanic eruptions emit large amounts of aerosols and gases into the atmosphere with severe implications on environment, climate, life on Earth, human society and aviation. The volcanic cloud ash concentration is one of the major challenges for aviation and, together with the particle size distribution and composition, is mostly unknown. Volcanic clouds are generally detected in the thermal infrared spectral range, but due to physical limitations, the ash particles can be retrieved only in the 0.5–15 μm radius range. The undetected "missing mass" composed by particles larger or smaller than this size interval is unknown and its estimation extremely challenging. Moreover, a precise knowledge of the ash composition is fundamental for a correct interpretation of the radiances received by remote sensing instruments and to reduce the volcanic cloud estimation uncertainties. Ash is usually emitted together with different gases (mostly H2O, CO2, SO2 and HCl) whose estimation is affected by significant errors. The volcanic cloud top and bottom height can be estimated with a coarse accuracy only so that also the thickness estimation is extremely challenging. To obtain a precise characterization of the cloud, direct sampling of the species at different altitudes is required. In this project, three innovative balloon borne systems, equipped with different instruments for ash and gases measurement and sampling, will be developed. A customized "volcanosonde" sensor package will be designed, manufactured and airlifted by sounding balloons in free-flying and tethered configurations or will be dropped by a high-altitude balloon from above the volcanic cloud. It will include a sensor package for ash (concentration and PSD), gases (H2O, CO2, SO2 and HCl) and atmospheric parameters (pressure and temperature) estimations, telemetry and monitoring system. A dedicated mission software will be also developed for the real time analysis of the data collected. All the configurations of the "volcanosondes" are planned to provide a profile of the species with a spatial resolution of at least 50 m. The tethered balloon will also provide a high temporal resolution and relatively long-term coverage, while the sensors dropped by the high-altitude balloon will be able to profile the cloud at different locations. This will allow us to make a precise estimation of the volcanic cloud structure, ash and gases parameters, thus to both improve and validate satellite, ground based and dispersion models products. After an extensive testing phase in the laboratory and in flight, a number of field campaigns will be organized on several Italian volcanoes having different topographic characteristics such as Vulcano, Stromboli and Etna. The results of the VOLANDO project will provide, for the first time, a comprehensive view of a volcanic cloud inner structure and composition contributing to understand volcanic processes and to mitigate the risks on both local population and airspace.