A Severe Weather QuickOSSE Examining the Impact of Super Constellations of GPS Radio Occultation Satellites

Global Navigation Satellite System (GNSS) radio occultations (RO) over the last 10 years have proved to be a valuable and unbiased data source for operational global numerical weather prediction. Since the launch in 2006, observations gathered by FormoSat-3/Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC-1) have typically numbered ~1,800 profiles/day globally, and COSMIC-2 when fully deployed will produce up to 10,000 profiles/day. However, this level of global sampling provides neither the spatial coverage nor the temporal updates that are dense enough or frequent enough to initialize evolving atmospheric structures at the mesoscale with any fidelity.

In our simulation study, we use the Quick Observing System Simulation Experiment (i.e., QuickOSSE) framework to measure the impact of vastly increased numbers of GNSS RO profiles on weather analysis and forecasting. Our study focuses on a severe convective weather event that occurred May 31, 2013, because this event produced both a very wide EF3 tornado (the so-called “El Reno” tornado) and flash flooding in Oklahoma City, Oklahoma. We use the Weather Research and Forecasting (WRF) model to compute our 2 km nature run, i.e., the “truth” in our study. And we use a 24-member, physics-based ensemble of 18-km-resolution WRF models, along with an Ensemble Kalman Filter (EnKF) to blend the simulated observations with the ensemble mean a priori model state vector. We use the WRF-DART ensemble data assimilation system to manage the hourly, cycling data assimilation and for its non-local, excess phase observation operator for RO data.

We simulate future constellations of RO satellites that can produce up to 2.5 million profiles/day globally. We will show analysis and forecast impacts of greatly increased numbers of RO profiles. The analysis impacts on lower tropospheric moisture fields in particular will be highlighted, as well as impacts on convective initiation in the forecasts.