Validation and evaluation of SEVIRI volcanic ash heights

The April-May 2010 eruptions of the Icelandic volcano Eyjafjallajokull provided a clear example of the disruptive effects volcanic eruptions can have on modern society. Due to the closure of European air space because of volcanic ash plumes, millions of travelers were stranded and air travel in, from and to Europe was disrupted for days to weeks. In the aftermath of the episode it became clear that on the one hand European regulations may have been too strict, while on the other hand there was a need for easy access to all available satellite information on volcanic ash.

For the European Volcanic Observatory Space Services project (EVOSS), this eruption could not have been more fortuitous with its kick-off in March 2010. The principal goal of EVOSS is to develop and demonstrate a portfolio of services based on earth observation products for monitoring volcanic activity and related hazards on a global scale.

One of the important products of this project is to make volcanic ash information derived from geostationary satellites available. Geostationary satellites have the advantage that they provide continuous information on the location of volcanic ash plumes, and thus are important for near-real time monitoring and potentially crucial for aviation industry. Research into the possibilities to retrieve information on volcanic ash from geostationary satellites – in particular quantitative information - had been going for quite some time, and at the moment of the Eyjafjallajokull eruption it was clear the current algorithm were sufficiently advanced for practical use.

Due to the political and societal recognition of satellite measurements as an important information source, EVOSS and the EUropean METeorological SATellite (EUMETSAT) organization quickly joined forces in order to make geostationary volcanic ash information available via the EVOSS service available. EUMETSAT had already initiated a pilot study into the capacity of a near-real-time service on volcanic ash, which led to the release of a report in April 2011 [Prata, 2011]. The main findings of the report were that quantitative information on volcanic ash could be retrieved from measurements of the Spinning Enhanced Visible and InfraRed Imager (SEVIRI), most importantly volcanic ash mass loading and ash height.

In parallel to the assessment of the EUMETSAT product, KNMI developed its own ash height product. Reason for doing so was on the one hand that at the time of the assessment it was unclear whether or not EUMETSAT was allowed to make its information available, and on the other hand there was an alternative to the methodology for calculation ash heights as done by EUMETSAT (see method section).

However, although EUMETSAT has implemented the Prata [2011] algorithm, which it dubbed “VOLE” and provides near-real time data, the quality of both the mass loading and ash height had yet to be determined. For the first task another pilot study was launched, and results were recently published [Prata and Prata, 2012]. The validation of ash heights was incorporated within the EVOSS work packages, and results from the validation study will be presented in this report.