Ionospheric Data Assimilation Analysis Using Ground-based GPS and Radio Occultation Observations
C. Y. Lin1, T. Matsuo2, 3, J. Y. Liu1, C. H. Lin4, H. F. Tsai4
1. Institute of Space Science, National Central University, Taoyuan, Taiwan
2. Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado, USA
3. Space Weather Prediction Center, National Oceanic and Atmospheric Administration, Boulder, Colorado, USA
4. Department of Earth Sciences, National Cheng Kung University, Tainan, Taiwan
Ionospheric data assimilation is a powerful approach to reconstruct the three-dimensional distribution of ionospheric electron density from various types of observations. The ionospheric data assimilation model based on the Gauss-Markov Kalman filter with the International Reference Ionosphere as the background model is used to assimilate two different types of total electron content (TEC) observations from ground-based GPS and space-based FORMOSAT-3/COSMIC (F3/C) radio occultation (RO). The Observing System Simulation Experiments (OSSEs) of assimilating FORMOSAT-7/COSMIC-2 (F7/C2) RO and ground-based GPS data in the data assimilation model are implemented, the OSSEs results demonstrate that the F7/C2 RO data can increase model accuracy more than assimilating F3/C RO data. The new ionospheric data assimilation model that employs the location-dependent background model error covariance, Kalman filter forecast step, and Kalman filter measurement update step could reconstruct the three-dimensional ionospheric electron density distribution satisfactorily from both ground- and space-based GPS observations.