Applications of satellite observations of volcanic ash in atmospheric dispersion modelling

Satellite observations have been instrumental in the detection and monitoring of hazardous airborne volcanic ash and in constraining atmospheric dispersion modelling for ash transport forecasting. Here we provide an overview of how they are used by modellers to interpret and evaluate output from volcanic ash dispersion and transport models and also inform the source terms used in those models. We include instances where satellite observations and model output have been used complementarily to glean information about ash episodes, and we give detailed examples of the use of observations in data assimilation. Using these examples we show how satellite observations have enabled the volcanic ash community to improve forecasts and better characterise uncertainty in model eruption source parameters. The dispersion modeller should be aware of the uncertainties and limitations attributable to satellite observations of ash, and how assumptions can affect interpretation of the observations. We give a brief discussion of some of these issues.