Application of Meteosat SEVIRI channel difference 0.6 μm-1.6 μm in convective cells detection

摘要

Convective cells detecting algorithms, used in operational weather services, are frequently based on single infrared channel data. Due to many disadvantages of these methods, an attempt is made to introduce the difference of Meteosat SEVIRI channels 0.6 μm and 1.6 μm as a tool for automatic recognition of convective clouds. The differences of reflectance values of the two channels were calculated for numerous cases and the results were visually compared to radar reflectivity data. The comparison shows that all potentially dangerous cells are detected which means promising and operationally applicable result. Due to the fact that satellite radiometer sees particles of a much smaller size than the radar does, the difference method suggested here enables the recognition of small developing cells several time-steps (up to 1 h) before they are seen in the radar imagery, provided that a proper threshold is set for the difference values. This enables the detection of convective cells in the areas not covered by radar measurements. It is also shown that the detection provided by the channel difference method is much more precise and detailed than the detection based on the IR channel data. The main disadvantage of the method is the fact that it can be used only during day-time so the night-time convection needs to be treated separately.