Angular Dependency Model for the Meteosat Longwave Radiation

The paper presents the longwave radiance–to–flux conversion which has been developped, implemented and is currently applied to produce the GERB Edition-1 data. The method is based on regressions on the SEVIRI thermal channels. Some results of the validations of this part of the processing are presented which indicate an underestimation of the limb–darkening in case of semi–transparent high clouds (cirrus). It is shown that this problem can be solved in part by using a specific regression for this kind of cloudiness. This work may be useful to improve the quality of the GERB thermal flux in subsequent Editions of the dataset.