Using multi-scale modeling and observations to link the eruption source parameters to the dispersion of volcanic clouds in case of the Raikoke eruption 2019

The Raikoke volcano emitted about 0.4-1.8 x 10⁹ kg of ash and 1-2 x 10⁹ kg of SO₂ up to 15 km into the atmosphere. However, the eruption was characterized by several puffs of different time periods and eruption heights. Here, we use the ICON-ART model in a model setup in which we resolve the phases of the Raikoke eruption. We calculated the eruption source parameters (ESPs) online by coupling ICON-ART to the 1-D plume model FPlume. The input heights for the different eruption phases needed for FPlume are geometrically derived from GEOS-17 satellite data. An empirical relationship is used to derive the amount of very fine ash (particles <32µm) which is relevant for long range transport in the atmosphere. In the first hours during and after the eruption, the modeled ash loading agrees very well with the observed ash loading from Himawari-8 due to the resolution of the eruption phase and the online calculation of the ESPs. In later hours, aerosol dynamical processes (nucleation, condensation, coagulation) explain the loss of ash in the atmosphere in agreement with the observations. However, a direct comparison is partly hampered by water and ice clouds overlapping the ash cloud in the observations. In case of SO₂, we compared 6-hourly means of model and Himawari data with respect to the structure, amplitude, and location (SAL-method). In the beginning, the structure and amplitude values differed largely because the dense ash cloud directly after the eruption leads to an underestimation of the SO₂ amount in the satellite data. On the second and third day, the SAL values are close to zero for all parameters indicating a good agreement of model and observations. We argue that representing the plume phases and ESPs in ICON-ART by FPlume enhances ash and SO₂ predictability in the first days after the eruption, especially in case of non-continuous volcanic eruptions like the Raikoke eruption 2019.