JPL/USC GAIM: On the impact of using COSMIC and ground-based GPS measurements to estimate ionospheric parameters

摘要

The University of Southern California (USC) and the Jet Propulsion Laboratory (JPL)have jointly developed the Global Assimilative Ionospheric Model (GAIM) to monitorspace weather, study storm effects, and provide ionospheric calibration for space weatherapplications. JPL/USC GAIM is a physics-based 3-D data assimilation model that usesboth four-dimensional variational analysis and Kalman-filter techniques to solve for theion and electron density state and key drivers such as equatorial electrodynamics, neutralwinds, and production terms. Here we report on GAIM Kalman filter-based assimilationresults using ground-based GPS and COSMIC-derived total electron count (TEC)measurements. We find that assimilating COSMIC measurements into GAIM improvescritical ionospheric parameters such as NmF2 and HmF2. Assimilating COSMIC dataproduces higher-accuracy vertical electron density profile "shapes," as verified bycomparisons to independent electron density profiles measured at Arecibo, Jicamarca, andMillstone Hill incoherent scatter radar (ISR). We also find significant improvement inglobal vertical TEC (VTEC) maps when assimilating COSMIC measurements, verified bycomparing GAIM output with VTEC measurements from the Jason ocean altimeter. For3 days in June 2006, improvement in accuracy compared to ground-data-onlyassimilation is found to be 30%, 28%, and 44%, respectively.