STUDY OF LIGHTNING INITIATION FROM MSG SUPER RAPID SCAN SERVICE OVER ITALY

MSG data from the EUMETSAT Super Rapid Scan Service (SRSS) have been used in conjunction with a high efficiency lightning network (LINET) to find relationships between MSG convection initiation fields and lightning activity at mid-­latitudes, specifically in the Mediterranean area. The objectives of this study are to obtain quantitatively estimates of the temporal gap between convection initiation and the onset of lightning activity and to infer cloud microphysical/dynamical characteristics leading to electrical activity. Infra-­red (IR) and water-­vapor (WV) channels together with High-­ Resolution Visible (HRV) data from MSG high time-­frequency acquisition mode (every 2.5 min) have been used in the study. The SRSS was available only for a few days on the European area. The lightning data were used to select events with intense electrical activity occurred during the SRSS periods. Lightning data were re-­gridded on SEVIRI grid (3 x 3 Km2 spatial resolution at nadir) in order to track the temporal and spatial evolution of the convective cells on the MSG IR fields. Positions of the convective cells during the pre-­lightning phase were extrapolated from IR brightness temperature (TB) fields, to be able to follow the time-­space evolution of the TB's associated to each cell in MSG IR channels up to 75 min prior to the lightning initiation. Different channel linear combinations were analyzed and the results indicate the presence of clear signs of convection already 45-­60 min prior to the first registered LINET strokes. The high temporal frequency of SRSS also allowed to observe the rapid evolution of explosive convective systems that developed within 15-­20 min prior to the first strokes. The convection initiation associated to this type of systems could not be observed in detail with the currently operational MSG acquisition mode. Results are encouraging on the possibility of using RSS of the future MTG (planned in 2019) for the nowcasting of intense convective events. More studies will be carried out when more SRSS data will become available prior to the launch of the MTG.