A channel selection for the assimilation of CrIS and HIRAS instruments at full spectral resolution

• Published in: Quarterly journal of the Royal Meteorological Society 2022-04, Vol.148 (744), p.1092-1112
• Main Author: Carminati, Fabien
• Format: Article
• Language: English
• Subjects: data assimilation; Global weather; Instruments; Meteorological satellites; numerical weather prediction; remote sensing; Resolution; Tropical climate; Weather forecasting
• ISSN: 0035-9009; 1477-870X
• DOI: 10.1002/qj.4248

A new channel selection is proposed for the processing of observations at full spectral resolution (FSR) from the Cross‐track Infrared Sounder (CrIS) and Hyperspectral Infrared Atmospheric Sounder (HIRAS) instruments in the Met Office global numerical weather prediction (NWP) system. The new selection has been derived in order to minimise the error in NWP analysis and has been compared to an existing selection developed at the National Oceanic and Atmospheric Administration (NOAA). Both selections have been tested in the Met Office global NWP system to investigate the use of FSR CrIS compared with the current normal spectral resolution (NSR) set‐up employed in operations. Improvements are obtained for most forecast variables up to 7‐day lead times, with change in root‐mean‐square error (RMSE) ranging from 0.13 to 0.54%, although degradation of tropical temperatures are noted for the NOAA selection. The background fit to observations from independent sounders improves by up to 0.8% with the new selection, outperforming the NOAA selection which results in degradations across most instruments. The assimilation of HIRAS observations does not however benefit the system. A new channel selection is proposed for the assimilation of observations at full spectral resolution (FSR) from the Cross‐track Infrared Sounder (CrIS) and Hyperspectral Infrared Atmospheric Sounder (HIRAS) instruments in the Met Office global numerical weather prediction (NWP) system. Significant improvements are obtained for most forecast variables compared to the assimilation of observations at normal spectral resolution (NSR). The new channel selection presents more benefits than that provided by NOAA. The assimilation of HIRAS observations does not benefit the system.