Volcanoes are a major source of gases and particles, and may be considered natural polluters of the atmosphere. There is a need to analyze emissions from volcanoes in order to attempt to understand how they behave, both physically and chemically. In this proof-of-concept study, the team will measure water and sulfur dioxide concentrations (both important volcanic gases) in situ in a volcanic plume and compare the results with a suite of ground-based remote sensing instruments. This is a novel idea based on new technology that allows direct measurement of the gases using miniature sensors. As the sensors are so small and light, it is possible to utilize unmanned aerial vehicles as a measurement platform, in this case, state-of-the-art remotely-operated controlled meteorological (CMET) balloons. These small altitude-controlled balloons are unique in that it is possible to perform vertical profiling or track specific layers in the atmosphere, and collect many hours of continuous data during each flight. The data collected will also be used to validate existing remote sensing techniques, and will provide a resource to develop and validate models of volcanic plume dispersion and evolution in the troposphere. Up to 3 CMET balloon flights will be carried out during a field campaign at Kilauea volcano, Hawaii, where there has been a persistent plume for over 20 years.
To fully understand the evolution of volcanic emissions in the atmosphere, physical and chemical parameters must be measured to provide data on which to build accurate models. Quantifying fluxes of volcanic gases to the atmosphere is important for assessing the potential impact on climate or as a precursory indicator of eruption. In situ measurements of volcanic emissions are sparse and are mostly restricted to aircraft sampling carried out ~20-30 years ago, an approach now considered to be extremely hazardous. To date there has not been a successful unmanned in situ volcanic plume aerial sampling investigation, but there is great demand for such data, for example to validate numerical models. Ground-based remote sensing of volcanic emissions is employed as a tool in both fundamental scientific research and hazards assessment to estimate gas fluxes to the atmosphere. Measurement of volcanic SO2 flux can be used as an indicator of changes in eruptive activity. Conversion rates of SO2 to sulfate aerosol are poorly constrained for tropospheric volcanic plumes, which can affect gas concentration measurements, decreasing the robustness of remotely-sensed SO2 flux.
This study will improve understanding of volcanic plume evolution through: (1) tracking of atmospheric parcels to investigate plume dispersion; (2) in situ measurement of H2O and SO2 concentration; (3) in situ measurement of SO2 concentration as a function of time to characterize the chemical evolution (SO2) of a volcanic plume; (4) analysis of plume mixing from accurate measurement of wind shear, thermal stability and profiles of H2O and SO2 concentration; and (5) investigation of the relationship between plume SO2 concentration and the source vent thermal properties as a function of time. Simultaneous ground-based remote sensing will be carried out using FLYSPEC/DOAS, UV-camera, thermal infrared thermometers and a thermal camera to generate continuous path-length measurements of SO2 concentration, SO2 plume imagery and thermal characterization of the plume at source, respectively. These additional data will be used to cross-validate CMET measurements and ground-based remote sensing techniques. This study will generate the first in situ measurements of volcanic plume composition and thermodynamic properties using a Lagrangian platform. Additionally, this will be the first time that in situ measurements of volcanic plume SO2 will be directly compared to commonly-used ground-based remote sensing techniques.
