High–Resolution Modeling of Airflows and Particle Deposition over Complex Terrain at Sakurajima Volcano

Abstract

The realistic representation of atmospheric pollutant dispersal over areas of complex topography presents a challenging application for meteorological models. Here, we present results from high–resolution atmospheric modeling in order to gain insight into local processes that can affect ash transport and deposition. The nested Weather Research and Forecasting (WRF) model with the finest resolution of 50 m was used to simulate atmospheric flow over the complex topography of Sakurajima volcano, Japan, for two volcanic eruption cases. The simulated airflow results were shown to compare well against surface observations. As a preliminary application, idealized trajectory modeling for the two cases revealed that accounting for local circulations can significantly impact volcanic ash deposition leading to a total fall velocity up to 2–3 times the particle’s terminal velocity depending on the size. Such a modification of the estimated particle settling velocity over areas with complex topography can be used to parametrize the impact of orographic effects in dispersal models, in order to improve fidelity.