Abstract
<div class="page" title="Page 1"><div class="layoutArea"><div class="column"><p><span>Quantifying volcanic ash emissions syneruptively is an important task for the global aviation community. However, due to the near real time nature of volcano monitoring, many parameters important for accurate ash mass estimates cannot be obtained easily. Even when using the best possible estimates of those parameters, uncertainties associated with the ash masses remain high, especially if the satellite data is only available in the traditional 10.8 and 12.0 μm bands. To counteract this limitation, we developed a quantitative comparison between the ash extents in satellite and model data. The focus is the manual cloud edge definition based on the available satellite reverse absorption (RA) data as well as other knowledge like pilot reports or ground-based observations followed by an application of the Volcanic Ash Retrieval on the defined subset with an RA threshold of 0 K. This manual aspect, although subjective to the experience of the observer, can show a significant improvement as it provides the ability to highlight ash that otherwise would be obscured by meteorological clouds or, by passing over different surfaces with unaccounted temperatures, might be lost entirely and thus remains undetectable for an automated satellite approach. We show comparisons to Volcanic Ash Transport and Dispersion models and outline a quantitative match as well as percentages of overestimates based on satellite or dispersion model data which can be converted into a level of reliability for near real time volcano monitoring. </span></p></div></div></div>
Highlights
Operational monitoring of erupting volcanoes and their ash emissions is crucial for aviation safety [Prata, 1989]
The analysis shows a large model excess (ME) area to the east of the cloud that coincides with the lower parts of the modelled ash cloud (approximately beof our analysis (August 10, 23:00 UTC)
This can be caused by wrong model parameters but, due to the patchy character of the area, false alarms based on meteorological cloud cover are more likely
Summary
Operational monitoring of erupting volcanoes and their ash emissions is crucial for aviation safety [Prata, 1989]. Space observations traditionally use satellite bands spectrally located around 10.8 and 12.0 μm as these have been found to have the ability to distinguish volcanic ash from meteorological clouds based on the reverse absorption (RA) feature discussed in Prata (1989). This method has a threshold of 0 K which is often reduced to a negative value to avoid false alarms [see Steensen et al, 2013]. Accuracy of satellite analyses and VATD predictions depends on their respective input
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