EUMETSAT Meteosat Third Generation (MTG) Lightning Imager: From mission requirements to product development

The Meteosat Second Generation (MSG) system has become the primary European source of geostationary observations over Europe and Africa with the start of nominal operations in January 2004, and delivering observations and services at least until 2018 through MSG-3 and to 2022 through MSG-4. However, considering the typical development cycle for a new complex space system, it was already for a longer time necessary to plan for and define the Meteosat Third Generation (MTG) system. As two Meteosat satellites need to be in orbit to fulfil the complete user needs, the first MTG satellite needs to be available for launch in 2017, before the end of the nominal lifetime of MSG-3. One of the new missions selected for MTG is the lightning Imagery (LI) mission, detecting continuously over almost the full disc the lightning discharges taking place in clouds or between cloud and ground with a resolution around 10 km over Europe. The LI mission is intended to provide a real time lightning detection (cloud-to-cloud and cloud-to-ground strokes) and location capability in support to Nowcasting (NWC) and Very Short Range Forecasting (VSRF) of severe storm hazards and lightning strike warning. As lightning is strongly correlated with storm related phenomena like precipitation, hail and gust, a further objective of the LI mission is to serve as proxy for intensive convection related to ice flux, updraft strength and convective rainfall. Lightning can also serve as proxy for adiabatic and latent heating to be assimilated in global/mesoscale NWP models. Finally, for atmospheric chemistry, lightning plays a significant role in generating nitrogen oxides. The natural nitrogen oxide budget is a matter of great uncertainty at this time, and long-term observations of one of its sources will prove valuable as the subject develops. The main objective of the mission is to detect flashes with a goal Detection Efficiency (DE) of better than 90%. This is in line with detecting risk areas for heavy convection which requires primarily information on flashes and their density in space and time but not on individual strokes composing the flash. A flash is linked with discharges forming one or more strokes visible as optical pulses at cloud top. The analysed statistics indicate that 90% of all flashes are linked with a stroke having at least one optical pulse of energy above 10 µJm-2sr-1. One task during the MTG preparatory program (Phase B) for EUMETSAT is the development of the Level 2 product processors, together with the user community. The primary L2 products are the detection of the optical pulses to be composed to flashes. The more advanced products are based on the statistics of these two LI products (e.g. flash densities and flash rates, storm related lightning characteristics, lightning warning, cell tracking, quantitative precipitation estimate, NOx production estimate). The paper discusses the MTG LI status, foreseen products and the status of the processor development for L2 products