Use of Meteosat imagery to define clouds linked with floods in Greece

A cloud classification scheme has been developed with the aim of defining and monitoring clouds cells associated with heavy rain. In the first stage of the scheme, Meteosat images in the visible were corrected to account for varying illumination times and angles. In the second stage, analysis of Meteosat images in the visible, infrared and water vapour channels resulted in the assignment of spectral signatures to seven categories of cloud class. The analysis was supported by temperature and humidity profiles from radiosondes in the wider geographical area as well as by synoptic maps of the area. Finally, Meteosat images reflecting two flood incidents which occurred in Greece on 21 October 1994 and 12 January 1997 were classified on the basis of the defined cloud categories; cloud cells associated with heavy rain were clearly depicted on the classified images through the category of thick opaque convective clouds.