MSG/SEVIRI cloud mask and type from SAFNWC

Abstract

Data from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) on board the first Meteosat Second Generation (MSG) satellite have been available since February 2003. Four MSG satellites are planned to ensure an operational service until at least 2018. A software package, which derives from MSG/SEVIRI imagery a set of 12 products useful for nowcasting purposes, has been developed cooperatively by the Satellite Application Facility for supporting NoWCasting and very short range forecasting (SAFNWC) and is distributed by EUMETSAT.

This paper describes the cloud mask (CMa) and type (CT) algorithms implemented in this SAFNWC/MSG software package. A multispectral thresholding technique has been used: the test sequence depends on illumination conditions and geographical location whereas most thresholds are dynamically computed from ancillary data (atlas, climatology maps, numerical weather prediction (NWP) model forecast fields) using radiative transfer models. These algorithms have been prototyped using GOES‐8 and MODIS imagery before being applied to MSG‐1/SEVIRI. The cloud mask and type can be extracted in any area inside the MSG full disk. Preliminary validation results obtained from a comparison with surface observations using a few months of MSG‐1/SEVIRI data show good performances.