Calculating and communicating ensemble-based volcanic ash dosage and concentration risk for aviation

During volcanic eruptions, aviation stakeholders require an assessment of the volcanic ash hazard. Operators and regulators are required to make fast decisions based on deterministic forecasts, which are subject to various sources of uncertainty. For a robust decision to be made, a measure of the uncertainty of the hazard should be considered but this can lead to added complexity preventing fast decision making. Here a proof-of-concept risk matrix approach is presented that combines uncertainty estimation and volcanic ash hazard forecasting into a simple warning system for aviation. To demonstrate the methodology, an ensemble of 600 dispersion model simulations is used to characterise uncertainty (due to eruption source parameters, meteorology and internal model parameters) in ash dosages and concentrations for a hypothetical Icelandic eruption. To simulate aircraft encounters with volcanic ash, trans-Atlantic air routes between New York (JFK) and London (LHR) are generated using time-optimal routing software. This approach has been developed in collaboration with operators, regulators and engine manufacturers; it demonstrates how an assessment of ash dosage and concentration risk can be used to make fast and robust flight-planning decisions even 23 when the model uncertainty spans several orders of magnitude. The results highlight the benefit of using an ensemble over a deterministic forecast and a new method for visualising dosage risk along flight paths. The risk matrix approach is applicable to other aviation hazards such as SO2 dosages, desert dust, aircraft icing and clear-air turbulence and is expected to aid flight-planning decisions by improving the communication of ensemble-based forecasts to aviation

Hydrogen gas monitoring at Long Valley Caldera, California

In response to the need for closer, systematic monitoring of the Long Valley as a means of detecting changes that might precede volcanic activity in the area, a systematic program was begun to study hydrothermal activity and gas emissions. The initial effort to monitor hydrogen gas on one component of the gas phase that might be given off by an ascending body of magma is described. Hydrogen is a component of most magmatic gases, and there is now evidence for the release of hydrogen from magmas at shallow crustal depths prior to volcanic eruptions. Hydrogen may also be produced in tectonically active areas by hydration reactions of rock-forming minerals with ground waters at depths where frictional stress results in moderately elevated temperatures. Because hydrogen is extremely mobile and relatively non-reactive once formed, it should ascend to the surface mobile and relatively non-reactive once formed, it should ascend to the surface easily through incipient fractures developed in tectonic fault zones. For these reasons, anomalous hydrogen emissions in the Long Valley area may be a good geochemical indication of tectonic or magmatic events