Global ionospheric electron density estimation based on multisource TEC data assimilation
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We developed a parameterized ionospheric electron density model based on the IRI-2012 model by spherical harmonic expansions in the horizontal and empirical orthogonal functions in the vertical. Then, after assimilating the monthly multisource total electron content (TEC) data from ground-based GPS, LEO radio occultation (RO), and the oceanic altimeter during magnetically quiet time into the model, we reanalyzed the monthly global ionospheric electron density TEC and other key parameters such as foF2 and NmF2. Both the reanalyzed and IRI-2012 model results were compared to the TEC measurements, the monthly median foF2 in a middle-latitude ionosonde station, and the global TEC map from CODE. The comparisons showed that both the reanalyzed and IRI results are consistent with those observations and the reanalyzed results perform better than the IRI model. Furthermore, the reanalyzed results are also consistent with the retrieved maps of HmF2, NmF2, and TEC from COSMIC RO observations. In summary, our method can reanalyze the global TEC and electron density using multisource TEC data assimilated into our model and improve the performance of IRI model.
KeywordsGlobal positioning system (GPS) Total electron content (TEC) Electron density International Reference Ionosphere (IRI) Data reanalysis
We acknowledge the use of data from the Chinese Meridian Project (CMP, http://www.meridianproject.ac.cn). We thank the COSMIC Data Analysis and Archive Center of UCAR for providing the reprocessed and post-processed LEO RO TEC and profiles of electron density. CODE GIM data were acquired from the NASA Earth Science Data Systems and archived and distributed by the Crustal Dynamics Data Information System (CDDIS). The ground-based GPS data were obtained mainly from CDDIS, and additionally from the Scripps Orbit and Permanent Array Center's California Spatial Reference Center (SOPAC/CSRC), the Crustal Movement Observation Network of China (CMONOC) and CMP. Jason-1 and Jason-2 altimeter data were downloaded from the Jet Propulsion Laboratory (JPL) and the National Oceanic and Atmospheric Administration's National Oceanographic Data Center (NOAA/NODC) data centers, respectively. The IRI software code was obtained from the solar–terrestrial models archive of NASA’s Space Physics Data Facility. The solar and geomagnetic activity indices were obtained from NOAA’s National Geophysics Data Center (NGDC). The foF2 data were accessed from the Space Physics Interactive Data Resource (SPIDR) of the NGDC. We acknowledge the support by the Thousand Young Talents Program of China. This work was supported by National Natural Science Foundation of China (41131066, 41321003, 41404127, and 41404128), project funded by China Postdoctoral Science Foundation (2015T80130), project supported by the Specialized Research Fund for State Key Laboratories, National Important Basic Research Project (2011CB811405), and the Chinese Academy of Sciences (KZZD-EW-01-2). We thank two anonymous reviewers for their constructive comments which have greatly improved the manuscript.
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