Precipitation estimations from geostationary orbit and prospects for METEOSAT Second Generation

For over two decades operational rainfall estimations from geostationary sa tellites have represented an ambitious aspiration of scientists and an iden tified need of operational meteorologists. A wide variety of infrared and c ombined visible and infrared methods have been proposed for the identificat ion of suitable relationships between satellite-observed cloud top radiativ e features and rainfall at the ground. Microwave-based retrievals, however, correlate rainfall and internal cloud microphysical features more successf ully. The most significant limitation, however, is the indirect character o f the retrieval that correlates microphysical and dynamical cloud character istics with rain amounts at ground level. METEOSAT Second Generation signal s a new era for geostationary satellites with its new 12 channel imager SEV IRI and 15 minute full-disk image repeat cycle. SEVIRI is expected to contr ibute significantly to a better characterisation of clouds and atmospheric stability by means of improved infrared calibration, radiometric performanc es, imaging frequency and multispectral image analysis. The significant inc rease of multispectral cloud observations is expected to provide new data f or the improvements of rainfall estimations from geostationary orbit. The a nticipated progress from enhanced imaging frequency and multispectral data for the definition of new techniques is discussed. Considerations for opera tional applications, chiefly for nowcasting, are also provided as they are the main goal of the satellite. Future developments and synergies with othe r geostationary and polar orbiting instruments, passive and active, are fin ally considered as the ultimate strategy for more accurate instantaneous ra infall estimations at all latitudes.