The Role of NWP Filter for the Satellite Based Detection of Cumulonimbus Clouds

The study investigates the role of NWP filtering for the remote sensing of Cumulonimbus 1 Clouds (Cbs) by implementation of 14 different experiments, covering Central Europe. These 2 experiments compiles different stability filter settings as well as the use of different channels for 3 the InfraRed (IR) brightness temperatures. As stability filter parameters from Numerical Weather 4 Prediction (NWP) are used. The brightness temperature information results from the IR SEVIRI 5 instrument on-board of Meteosat Second Generation satellite and enables the detection of very cold 6 and high clouds close to the tropopause. The satellite only approaches (no NWP filtering) result 7 in the detection of Cbs with a relative high probability of detection, but unfortunately combined 8 with a large False Alarm Rate (FAR), leading to a Critical Success Index (CSI) below 60 %. The false 9 alarms results from other types of very cold and high clouds. It is shown that the false alarms can be 10 significantly decreased by application of an appropriate NWP stability filter, leading to the increase 11 of CSI to about 70 % . A brief review and reflection of the literature clarifies that the this function 12 of the NWP filter can not be replaced by MSG IR spectroscopy. Thus, NWP filtering is strongly 13 recommended to increase the quality of satellite based Cb detection. Further, it has been shown that 14 the well established convective available potential energy (CAPE) and the convection index (KO) 15 works well as stability filter. 16