Assessment of the Impact of FORMOSAT-3/COSMIC and FORMOSAT-7/COSMIC-2 GNSS RO Observations on Mid- and Low-Latitude Ionosphere Specification using the GSI Ionosphere Data Assimilation System

The Formosa Satellite-7/Constellation Observing System for Meteorology, Ionosphere, and Climate-2 (FORMOSAT-7/COSMIC-2) Global Navigation Satellite System radio occultation (RO) payload can provide valuable profiling of the ionized atmosphere with an unprecedentedly high spatial temporal resolution. Recently, a new ionospheric data assimilation system, the Community Gridpoint Statistical Interpolation (GSI) Ionosphere, is constructed with the National Oceanic and Atmospheric Administration GSI Ensemble Square Root Filter and the Global Ionosphere Plasmasphere and the Thermosphere Ionosphere Electrodynamic General Circulation Model. In this study the capability of the GSI Ionosphere to reconstruct realistic features of the mid- and low-latitude ionosphere is demonstrated with actual FORMOSAT-3/COSMIC RO slant Total Electron Content (sTEC) data for January 2013. Extensive observing system simulation experiments for FORMOSAT-3/COSMIC and FORMOSAT-7/COSMIC-2 missions are conducted to calibrate key Ensemble Square Root Filter parameters, including the number of ensemble members and the covariance localization, and then to assess the impact of the RO sTEC data on specification and forecasting of the mid- and low-latitude ionosphere. The GSI Ionosphere is expected to help reveal instantaneous global pictures of the day-to-day ionospheric variability from the upcoming FORMOSAT-7/COSMIC-2 mission.