On the usage of the Aviation Colour Code system at European Volcano Observatories: experiences and open questions

Abstract 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, 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 (ACC) 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 ACC. The comparative analysis presented here reveals that not all VOs in Europe use the ACC as part of their operational response, mainly because of a lack of volcanic eruptions since the ACC was officially established, or the absence of a formal appointment as an SVO. We also note that the VOs, which do regularly adopt ACC, operate differently depending on the frequency and styles of eruptions, the historical eruptive activity, the nature of the unrest, the monitoring level, and also on the agreement they may have with the local Air Transport Navigation providers. This study shows that even though the ACC system was designed to provide a standard, its usage strongly depends on the evaluation of the actors responding to the volcano emergencies. Some common questions have been identified across the different (S)VOs that will need to be addressed by ICAO in order to have a more harmonised approach and usage of the ACC.