Enhancing our understanding of volcanic clouds using long-term satellite records and next-generation instruments

Ash and gas produced during volcanic eruptions can have far-reaching impacts. Volcanic clouds feature on the UK National Risk Register because of the hazard to aircraft. They also affect atmospheric dynamics and chemistry, and alter the Earth’s climate – the latter being under-represented in the IPCC reports. Monitoring is critical for evaluating hazards and impacts, and satellite data, which offers frequent global coverage, is essential for this.
Typically, different volcanic cloud species are considered separately – a paradigm that is changing. Ash has been the focus for aviation. However, volcanic gases can lower cabin air quality and can have longer term impacts on the aircraft’s condition. Additionally, recent studies have demonstrated that ash can impact the atmospheric lifecycle of sulfur dioxide (SO2), and therefore the climate impact. Furthermore, climate modelling relies on estimates of the total SO2 mass for initialisation. However, the 2022 Hunga eruption saw rapid formation of sulfuric acid (H2SO4), raising a concern of whether models should be initialised based on SO2 alone. Other eruption characteristics such as carbon dioxide (CO2) emissions and ash composition, are poorly constrained across the globe.
The shift towards a holistic understanding of the combined impacts of volcanic ash and gas can only be delivered if supported by high-quality observations of multiple species. The Oxford Hyperspectral Atmospheric Retrieval Package (Ox-HARP) is a novel tool for quantifying information about SO2, H2SO4 and volcanic ash using satellite data. Unlike previous methods, it obtains information about different species simultaneously, offering a more comprehensive representation of volcanic clouds.
We are entering an exciting era for satellite-based remote sensing. This is driven by two important developments; firstly, we have extensive, long-term, consistent datasets, enabling us to improve our knowledge of the behaviour and impacts of volcanic clouds. Secondly, the next-generation of satellite instruments will provide higher-frequency measurements, and offer the capability to measure new gases. Together, these advances will revolutionise hazard monitoring and greatly enhance impact assessments in the coming years.
During this fellowship I will expand Ox-HARP to include next-generation satellite instruments and increase functionality (e.g. CO2 emissions and ash composition). I will use Ox-HARP to generate multi-species, multi-instrument and multi-decadal datasets on volcanic clouds, including new eruptions which take place during the fellowship. I will use this to explore two themes that span atmospheric science and volcanology:
(1) Improved characterisation of volcanic emissions and their early evolution. I will (i) explore how ash type (linked to magma composition) varies globally and during eruptions; (ii) quantify CO2 emissions at volcanoes; (iii) improve estimates of volcanic emissions that can be used to initialise dispersion and climate-impact models.
(2) Investigation of the factors influencing the long-term evolution of volcanic clouds. I will evaluate the factors affecting the lifetime of SO2 and ash in the atmosphere, which will be used improve process representation within climate and dispersion models.
Working with project partners I will ensure that the developed software is valuable in an operational context. And through collaborations with established researchers in the field of volcano-climate interactions, the scientific findings of the fellowship will be used to improve models and inform their future developments. The software, datasets and insights produced by this fellowship will strengthen our ability to respond to volcanic eruptions more effectively in the future.