Identifying an Observation Saturation Threshold for GNSS Radio Occultation Profile Assimilation in GFS

Global Navigation Satellite System (GNSS) Radio Occultation (RO) profiles have become an integral part of the atmospheric observation system. Assimilation of these observations into the NOAA/NCEP Global Forecast System (GFS) have decreased biases, improved analyses, and reduced forecast errors. Currently, approximately 10,000 RO profiles per day are read into the Gridpoint Statistical Interpolation (GSI) as part of creating the analysis. Using an Observing System Simulation Experiment (OSSE), we can identify a "saturation" threshold, defined here as the number of assimilated RO profiles per day at which further increases in assimilated RO profiles yield negligible analysis and forecast improvements. Results of investigating the impact of 10k, 50k, and 50k+ assimilated profiles/day will be shown.