Monitoring volcanic ash by using geostationary satellite

Volcanic hazards are of major national and international importance, affecting many regions of the globe and potentially having an impact on people both on the ground and in transit in the air. The authors of this paper have been involved as part team in the GMES FP7 'Downstream' Service project called EVOSS (European Volcano Observatory Space Services) aiming at developing a portfolio of services for supporting the volcanic hazard monitoring. In the framework of this project a study of the possibility of detecting the components of volcanic eruption has been carried out investigating, in appropriate bands of the electromagnetic spectrum (6.25, 8.7, 10.8, 12 mu m), the values of the brightness temperature. The results have been achieved by means of a combined use of numerical simulations, devoted to examining the behavior of the atmosphere gases and volcanic components, and remotely sensed satellite images. The processed images come from the SEVIRI (Spinning Enhanced Visible and InfraRed Imager) sensor on board the geo-stationary satellite Meteosat Second Generation (MSG). When the monitoring system was tested by using real-time data from MSG it became clear the need of improving the cloud mask algorithm in order to minimize the false alarms. This paper describes the technique followed to minimize the impact of clouds on the detection of ash plume. The priority was given to the reduction of false alarms, that is: confuse meteorological clouds with ash and provide plume extension much larger than the actual size.