The Sounding Capability from the Future Geostationary Extended Observations (GeoXO) Satellites

NOAA’s next Geostationary Extended Observations (GeoXO) mission will carry a hyperspectral infrared (IR) sounder (GXS) in addition to the advanced IR Imager (GXI), which is similar to the advanced baseline imager that currently exists in the Geostationary Operational Environmental Satellite (GOES-R) series. The GeoXO will thus have much improved sounding capabilities compared to the GOES-R series. With 1563 sounding channels available in the longwave and midwave spectral bands, GXS will provide the high vertical resolution of temperature and moisture information that is needed in numerical weather prediction (NWP) models. In addition, it will provide the higher temporal and higher spatial (4km at nadir) resolution information that is needed for the short term and near term forecasts. To evaluate the potential impacts of the GXS measurements on the temperature and moisture profile retrievals, a simulation study is carried out in this research based on the GXS performance and operational requirements. First, the theoretical analyses of information content, such as the degrees of freedom, are done for the GXS and GXI, as well as for the sounders flying on the low earth orbit (LEO) (e.g., CrIS). The possible impacts of GXS spectral coverage changes from basic requirement and an extra water vapor band at 5.1 µm of GXI are also investigated. Then the sounding retrievals are further explored using a machine learning technique to help understand the unique value of GXS in comparison to GXI and LEO sounders. Finally, a nowcasting OSSE (Observing System Simulation Experiments) for a regional severe storm case, derived from the ECMWF IFS Experimental Nature Run at 1-km (XNR1K), will be run using the same technique. The results of this OSSE will demonstrate the benefits of GXS in providing useful nowcasting products for local severe storms.