An empirical orthogonal function analysis of electron density profiles retrieved by GPS radio occultation
Kang-Hung Wu, Yen-Hsyang Chu, Ching-Lun Su
Institute of Space Science, National Central University, Chung-Li, Taiwan
GPS radio occultation (RO) was a powerful technique that provide a great number of electron density profiles in the whole world. It was widely accepted that the asymmetry of ionospheric electron density distribution was the main case of GPS RO retrieval error. This study demonstrated an empirical orthogonal function (EOF) analysis of electron density profiles retrieved by GPS RO. The IRI model were selected to simulate temporal and spatial electron density distribution from 80 to 2000 km. The COSMIC geometry was utilized to retrieve the electron density profile. Based on this simulation work, the IRI and the retrieved electron density were separately analyzed by EOF analysis method. The EOF decomposition shows the first four EOFs components express nearly 99.9 % of total variance. The comparisons of EOFs component between IRI and retrieved electron density are almost the same in first and second EOF, but the third EOF are totally different, which may be possible the source of the RO retrieval error.