Ash and Ice Aggregation in Satellite Retrieval: The 15 January 2022 Hunga Tonga‐Hunga Ha'apai Hydromagmatic Eruption

Abstract Explosive volcanic eruptions inject volcanic particles, such as ash and water vapor, into the atmosphere. Ice enriched volcanic clouds can hide the presence of silicate particles, intensifying the fatal risks for aviation. In this scenario, satellite monitoring systems play a key role in volcanic hazard mitigation. Thanks to the full disk perspective over the Pacific Ocean, the GOES‐17 geostationary satellite observed the 15 January 2022 Hunga Tonga‐Hunga Ha'apai hydromagmatic eruption. The explosive activity produced two volcanic clouds dispersing at different altitudes. In this work, we first focus on the altitude estimates of the two volcanic clouds, by means of volcanic cloud speed and wind components. Next, we study how the fine ash (64 μm diameter) total mass in atmosphere varies depending on the assumed fraction of ash and ice in an aggregate. Based on our estimates, the upper volcanic cloud disperses between 27.35 3.01 and 29.13 3.20 km altitude; the lower cloud between 14.02 1.54 and 14.8 1.63 km altitude. The estimated fine ash total mass doubles if we consider spherical aggregates instead of irregular aggregates, due to a tighter packing of coating particles. The highest estimated fine ash mass for the upper and lower clouds is of kg (12:40 UTC) and of kg (13:50 UTC), respectively. Estimating the exact amount of erupted fine ash mass, mainly during hydromagmatic eruptions, is challenging and further works should investigate aggregates where the ice fraction is higher than the ash fraction.