The European Volcano Observatories and their use of the aviation colour code system

Volcano observatories (VOs) around the world are required to maintain surveillance of their volcanoes and inform civil
protection and aviation authorities about impending eruptions. They often work through consolidated procedures to
respond to volcanic crises in a timely manner and provide a service to the community aimed at reducing the potential
impact of an eruption. Within the International Airways Volcano Watch (IAVW) framework of the International Civil
Aviation Organisation (ICAO), designated State Volcano Observatories (SVOs) are asked to operate a colour coded
system designed to inform the aviation community about the status of a volcano and the expected threats associated.
Despite the IAVW documentation defining the different colour-coded levels, operating the aviation colour code in a
standardised way is not easy, as sometimes, different SVOs adopt different strategies on how, when, and why to change
it. Following two European VOs and Volcanic Ash Advisory Centres (VAACs) workshops, the European VOs agreed
to present an overview on how they operate the aviation colour code. The comparative analysis presented here reveals
that not all VOs in Europe use this system as part of their operational response, mainly because of a lack of volcanic
eruptions since the aviation colour code was officially established, or the absence of a formal designation as an SVO.
We also note that the VOs that do regularly use aviation colour code operate it differently depending on the frequency
and styles of eruptions, the historical eruptive activity, the nature of the unrest, the monitoring level, institutional norms,
previous experiences, and on the agreement they may have with the local Air Transport Navigation providers. This study
shows that even though the aviation colour code system was designed to provide a standard, its usage strongly depends
on the institutional subjectivity in responding to volcano emergencies. Some common questions have been identified
across the different (S)VOs that will need to be addressed by ICAO to have a more harmonised approach and usage of
the aviation colour code.