THE EXPLOITATION OF METEOSAT SECOND GENERATION DATA IN THE MET OFFICE Roger Saunders, Richard Francis, Pete Francis, Joanne Crawford, Andy Smith, Ian Brown, Ruth Taylor, Mary Forsythe, Marie Doutriaux-Boucher and Sarah Millington Met Office, Exeter, U.K. Abstract The Met Office has been using data from the Meteosat Second Generation (MSG) satellite, Meteosat-8, both for data assimilation and forecast guidance applications since September 2004. This paper gives an overview of the range of MSG products developed at the Met Office and now being used by the nowcasting system, numerical weather prediction models and forecasters on a routine basis. INTRODUCTION In January 2004 the new Meteosat Second Generation (MSG) satellite MSG-1 was declared operational by EUMETSAT and was reassigned to be Meteosat-8. However at that time the Met Office and its customers were still reliant on the products from the Meteosat-7 first generation satellite. A project was initiated firstly to replace the Meteosat-7 products with Meteosat-8 products to ensure continuity after the termination of the Meteosat-7 service in June 2006. A second project was also set up to develop new or enhanced products, exploiting the new capabilities of the SEVIRI radiometer on the Meteosat-8 satellite, for nowcasting, NWP assimilation and imagery applications. The latter to provide support for the forecasters before they issue their guidance. This paper summarises some of the new products which have been developed for both applications and are now operational at the Met Office. There is also a newly developed satellite precipitation rate product derived from MSG imagery which is described in a companion paper in this proceedings (Francis et al., 2006) In addition to specific derived imagery products described here there is a set of ‘RGB’ imagery products tailored to specific meteorological situations which are also made available to the forecaster. PRODUCTS FOR NOWCASTING Meteosat-8 data is received directly at the Met Office via the EUMETCAST system and then processed on the Autosat system in real time to produce products for nowcasting, imagery for forecasters and NWP applications (see below). Images are received every 15 minutes and processed for nowcasting applications although only the European area is processed at this frequency. Full disk imagery is processed at a lower frequency. The products for nowcasting applications derived on Autosat are passed to the Nimrod nowcasting system (Golding, 1998). Some of the products delivered to Nimrod are also passed on to the NWP models for assimilation but at a lower frequency. Cloud Products The nowcasting system requirement is for cloud products sampled every 30 minutes generated within 3 minutes of the end of the measurement. MSG has a set of channels designed to provide accurate cloud top pressure and amount estimates. The first step in deriving cloud parameters is to produce a cloud mask which identifies clear, partly cloudy and fully cloudy fields of view using techniques previously developed for the AVHRR (e.g. Saunders and Kriebel, 1988). However an important development for processing MSG radiances is to include clear sky simulated radiances produced using NWP model profiles input to a fast radiative transfer model. This allows the differences between