Update on the Geostationary Extended Observations Sounder radiance proxy datasets

The nation's first geostationary advanced hyperspectral resolution infrared sounder, known as the Geostationary Extended Observations (GeoXO) Sounder (GXS), is scheduled for launch in the mid-2030s. GXS will offer unprecedented sounding capabilities that are critical for weather forecasting and nowcasting. In support of this mission, CIMSS has developed Version 1 (V1) of GXS radiance proxy datasets, which include three local severe storm cases and one full disk case. These datasets are based on the 1 km-resolution global experimental nature run (XNR1K) from the European Centre for Medium-range Weather Forecasts’ Integrated Forecast System, utilizing the Pressure-layered Fast Atmospheric Transmittance (PFAAST) model, with the assumption of a Fourier Transform Spectrometer (FTS). In 2024, BAE Systems was selected by NASA as the vendor to build the GXS instrument, which will be a grating spectrometer system. BAE Systems has provided the prototype GXS spectral response function (SRF) and the current best estimate noise equivalent delta radiance (NEdN). The new GXS will feature more channels, finer spectral resolutions, finer spectral sampling distance, and smaller NEdN compared to those used for V1 proxy datasets, which was based on the Performance and Operation Requirement Document (PORD) at that time. These enhancements will significantly impact the sounding information content of GXS radiances. To accommodate these changes, Version 2 of the GXS radiance proxy datasets will been generated for the same XNR1K using the PFAAST model updated with the BAE SRF. Examples of applications using the GXS proxy datasets will be provided.