Use of inter-channel correlations for assimilation of IASI Raw Radiances and Reconstructed Radiances in the DWD EnVar
Satellite data today is a core ingredient of state-of-the-art systems of numerical weather prediction (NWP). With new hyperspectral infrared atmospheric sounding instruments especially MTG-IRS and IASI-NG the operational data streams face great challenges with increasing amounts of data for processing and assimilation in NWP. Compression methods like principal component analysis (PCA) provide a promising tool to reduce data amount with the capability of noise reduction while maintaining the core information content.
The use of Reconstructed Radiances from principal component scores of the Infrared Atmospheric Sounding Interferometer (IASI) is being investigated in comparison to Raw Radiances in the operational setup of the ensemble variational data assimilation system (EnVAR) for the global ICON model of Deutscher Wetterdienst (DWD). The study is based on the operational PCA data stream disseminated by EUMETSAT.
The current focus is on the impact of observation error specification and inter-channel correlations for both types of data, Raw Radiances and Reconstructed Radiances.
Ms. Silke May DWD