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MSG/SEVIRI -- Effective BT for IR bands

Since May 5 2008 08:00UTC, EUMETSAT changed the definition of radiance in L1.5 level SEVIRI images to "effective" radiance.

Since then, the "equivalent blackbody temperature" will be calculated by Planck function using the calibration parameters provided by McIDAS system at SSEC. Before that time, the "spectral blackbody temperature" is returned by the same procedure. EUMETSAT provided a quick fix method (polynomial fit, not shown) to convert the "spectral blackbody temperature" to "equivalent blackbody temperature".
The figure below shows the difference between the two kinds of brightness temperature. MSG_calibration_effective_and_spectral_BT.png