Modeling of GPS total electron content over the African low latitude region using empirical orthogonal functions

Abstract

Abstract. In this paper, an empirical total electron content (TEC) model and trends in TEC over the African low latitude region are presented. GPS-derived TEC data from Malindi, Kenya (geographic coordinates 40.194° E, 2.996° S) and global ionospheric maps (GIMs) were used. We employed empirical orthogonal function (EOF) analysis method together with least square regression to model the TEC. The EOF-based TEC model was validated through comparisons with GIMs, GPS-derived TEC and TEC derived from the International Reference Ionosphere-2016 (IRI-2016) model for selected quiet and storm conditions. The single station EOF-based TEC model over Malindi satisfactory reproduced the known diurnal, semiannual and annual variations in the TEC. Comparison of the EOF-based TEC model results with TEC derived from IRI-2016 model showed that the EOF-based model predicted the TEC over Malindi with less errors than the IRI-2016. For the selected storms, the EOF-based TEC model simulated the storm time TEC response over Malindi better than the IRI-2016. In the case of the regional model, the EOF-based TEC model was able to reproduce the TEC characteristics in the equatorial ionization anomaly region. The EOF-based TEC model was then used as a background in estimating TEC trends. A latitudinal dependence in the trends was observed over the African low latitude region.

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“…Andima et al. (2019) recently reported on trends in TEC in the African low‐latitude region, confirming strong spatial variations in trends, largely organized by the magnetic field. Further studies monitoring the long‐term changes in TEC in the region most affected by main magnetic field changes, that is, also over the Southern Atlantic ocean and South America, will be important to help build up a picture of the spatial structure of long‐term changes in TEC and control for any effects on satellite‐based data applications that require long‐term measurement stability.…”