Evaluation of NOAA Commercial Radio Occultation Soundings in Global Weather Forecasting

NOAA began operational assimilation of Radio Occultation (RO) observations from the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC-1) mission over fifteen years ago. Since then, other operational and research missions have been incorporated into the operational suite. In order to increase the volume of RO profiles and their geographical coverage beyond what COSMIC-2 provides, which is mostly limited to the tropical and sub-tropical regions, NOAA engaged in procurement activities with commercial companies capable of delivering RO data for operational use. Tests were conducted in this study to quantify the value of commercial RO data for numerical weather prediction (NWP) applications, and their relative value compared to an U.S. Government RO data source (namely, COSMIC-2). When commercial RO soundings are added to a baseline that already assimilates COSMIC-2 bending angle observations, it is found that commercial RO soundings bring benefits to global weather forecast skill, mostly by reducing the temperature and wind root-mean-squared error globally. As expected, the benefits are larger in the extratropics. Statistics between COSMIC-2 and commercial RO data show similar values, indicating that higher signal-to-noise values are not necessary to improve weather forecasting - at least with current modeling capabilities. The quality of commercial RO is sufficient for current global NWP applications. Finally, and supporting earlier studies with simulated data, results show that global RO data distribution is needed to improve NWP skill globally.