One operational product derived from the Meteosat Second Generation (MSG) satellite is the Global Instability Index (GII). The GII is an airmass parameter indicating the stability and total precipitable water content of the clear atmosphere. The usefulness of this product has been demonstrated in many nowcasting applications in particular to identify regions of potential severe thunderstorms and related hazardous weather.

The MSG based GII retrieval currently uses forecast profiles from the European centre of Medium Range Weather Forecasts (ECMWF) as first guess or background profiles, which – due to the limited spectral information provided by MSG – given the final product a rather strong dependence on the forecast fields.

A combination with temperature and humidity profiles obtained from the hyperspectral measurements of the IASI instrument (Infrared Atmospheric Sounding Interferometer onboard EUMETSAT's Metop-A satellite) with the MSG measurements is investigated. The IASI sounding profiles are used as initial input to the GII retrieval, where the temporal evolution of the air mass properties can then be recorded by the geostationary MSG observations. Specific case studies for severe convective events will be presented, which show the potential and limitations of this approach.