First results on a process-oriented rain area classification technique using Meteosat Second Generation SEVIRI nighttime data

摘要

A new technique for process-oriented rain area classification using Meteosat SecondGeneration SEVIRI nighttime data is introduced. It is based on a combination of theAdvective Convective Technique (ACT) which focuses on precipitation areas connected toconvective processes and the Rain Area Delineation Scheme during Nighttime (RADS-N) a newtechnique for the improved detection of stratiform precipitation areas (e.g. in connection with mid-latitude frontal systems).The ACT which uses positive brightness temperature differences between the water vapour(WV) and the infrared (IR) channels (ΔT_WV-IR) for the detection ofconvective clouds and connected precipitating clouds has been transferred from Meteosat FirstGeneration (MFG) Metesoat Visible and Infra-Red Imager radiometer (MVIRI) to MeteosatSecond Generation (MSG) Spinning Enhanced Visible and InfraRed Imager (SEVIRI).RADS-N is based on the new conceptual model that precipitating cloud areas are characterised by alarge cloud water path (cwp) and the presence of ice particles in the upper part of the cloud. Thetechnique considers information about both parameters inherent in the channel differencesΔT_3.9-10.8, ΔT_3.9-7.3, ΔT_8.7-10.8, andΔT_10.8-12.1, to detect potentially precipitating cloud areas. All fourchannel differences are used to gain implicit knowledge about the cwp. ΔT_8.7-10.8 and ΔT_10.8-12.1 are additionally considered to gain information about the cloud phase.First results of a comparison study between the classified rain areas and corresponding ground basedradar data for precipitation events in connection with a cold front occlusion show encouragingperformance of the new proposed process-oriented rain area classification scheme.