Evaluating Impact of GNSS Radio Occultation Observations from CubeSats in a Hybrid Ensemble-Variational Data Assimilation System
It has already been demonstrated that Global Navigation Satellite System (GNSS) Radio Occultation (RO) observations have a significant impact on the forecast results, at the level equivalent to other most impactful data (e.g., AMSU-A, IASI, AIREP and AIRS data). At Spire Global, Inc., we are launching hundreds of small satellites (CubeSats), which can quickly provide additional, high-quality RO data and improve forecast results even further. The quality and usefulness of Spire RO data are currently being evaluated by various agencies, including NOAA, NASA, US Air Force and UK Met Office. We are also evaluating our own RO data, employing advanced data assimilation and forecasting methods.
The main focus of this presentation is the impact of Spire RO observations in a hybrid ensemble-variational Data Assimilation (DA) system. The DA system is based on an Ensemble Kalman Filter and a 4-Dimensional Ensemble Variational (EnKF-4DEnVar) approach. We evaluate the impact of Spire RO observations in the presence of other conventional and satellite observations, typically assimilated in weather forecasting centers. We are examining the impact of RO data on temperature and humidity profiles and evaluate its potential for improving cloud and precipitation forecasts, especially in the short range (up 24 h) forecast horizons.
Dr. Dusanka Zupanski Spire Global, Inc.