Initial notification that an eruption has occurred usually comes from eyewitnesses or volcano monitoring centres, but this can be a slow and unreliable process, particularly for volcanoes in isolated areas.
The Met Office has developed an automatic volcanic eruption detection system using Meteosat infrared images and forecast meteorological data. The system offers half-hourly monitoring of volcanoes over a wide field of view which includes Iceland, Europe, Africa and the Atlantic.
The detection algorithm looks for clouds which exhibit characteristics consistent with them being volcanic in origin.
Clouds are identified as having the correct shape for volcanic ash by checking for good shape correlation between the actual cloud and the cloud that might be expected for an eruption cloud in the prevailing meteorological conditions.
In order to rule out as many false alarms as possible, the cloud must also pass the following checks to give sufficient confidence that it is not a meteorological cloud.
The eruption detection system detected two thirds of the eruptions upon which it was tested, and could monitor the London VAAC's area of responsibility with the production of between one and two false alarms each day. In 2004 the system was upgraded to use Meteosat Second Generation images and was implemented onto the Met Office Satellite Processing System.