Quantifying Information Content of GNSS Radio Occultation Observations from Spire Global CubeSats

Multiple studies have shown that incorporating Global Navigation Satellite System (GNSS) Radio Occultation (RO) observations into data assimilation systems has a significant positive impact on the forecast results. Due to their low-cost and rapid deployment, emerging Low Earth Orbit (LEO) CubeSats are poised to dramatically increase the availability of new observations and GNSS RO benefits. An important question that needs an answer is whether the new CubeSats can provide data equivalent in quality and impact as that collected by more traditional satellites, COSMIC, MetOp, GRACE and CHAMP. To answer this question, Spire Global, Inc., is collecting, processing, assimilating and validating its own GNSS RO data. We also participate in third-party RO data evaluation projects, such as the NOAA Commercial Weather Data Pilot (CWDP) project, which was successfully completed in April 2017.

In this presentation we evaluate Spire RO data by means of information content analysis in order to answer the following: (1) Is the information content of the Spire RO data comparable to the information content of other GNSS RO data (e.g., from COSMIC, MetOPA and MetOpB instruments)? (2) In which weather situations and geographic domains does the Spire RO data bring the most information?

The results will be presented and evaluated in terms of globally varying, flow-dependent degrees of freedom for signal (DFS), employing Maximum Likelihood Ensemble Filter (MLEF) data assimilation approach and a global forecast model. Advantages of flow-dependent (vs. static) DFS will also be evaluated and discussed.