Attracting structures in volcanic ash transport

Volcanic ash clouds are a natural hazard that poses direct threats to aviation safety. Many volcanic ash transport and dispersion (VATD) models have been developed to forecast trajectories of volcanic ash clouds and to plan safety measures in the events of eruptions. Predictions based on these models are heavily dependent on accuracy of wind fields and initial parameters of ash plumes. However, these data of high accuracy are usually difficult to obtain, leading to possible inaccurate predictions of ash clouds trajectories using VATD models. In this study, a new method is developed to predict volcanic ash transport. In contrast to many existing VATD models that simulate the evolution of volcanic ash clouds, the new method focuses on the overall properties of the wind field in which volcanic particles are transported and correlates particle motion to the attracting structures that dictate the transport. As demonstrated in the study of Eyjafjallajökull eruption in Iceland in April, 2010, these structures act as attractors in the atmosphere towards which volcanic ash particles are transported. These attracting structures are associated with hazard zones with high concentrations of volcanic ash. The advantages of the method are that the attracting structures are independent of particle source parameters and are less prone to inaccuracy in the wind field than particle trajectories. The new approach provides the hazard maps of volcanic ash, and is able to help improve long-term predictions and to plan flight route diversions and ground evacuations.