Assessment of IRI-2016 hmF2 model predictions with COSMIC observations over the African region

Abstract

With significant advancement in the climatological nature of the International Reference Ionosphere (IRI) through a series of editions, the ionospheric community now focuses on possible improvements in the IRI Real-Time Assimilative Model (IRTAM) for describing the real-time weather conditions in the ionosphere. In line with the focuses of the global research community, the present study intends improving the critical ionospheric electron density height (hmF2) predictions in the latest version of the IRI model (IRI-2016) through a comparative analysis with the hmF2 derived from the Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) ionospheric occultation profiles over the African region under various solar and geomagnetic conditions. As the existing operational ionosondes (only five in number) are not evenly distributed across the African region, the dense COSMIC soundings offer an excellent opportunity for assessing the IRI hmF2 model performance over the region. The study includes a comparative study of observed COSMIC hmF2 values with IRI-2016 predictions, almost covering the whole solar cycle (2007 to 2017). The comparison is based on statistical model validation metrics for datasets under various solar and geomagnetic conditions. The average performance of the IRI hmF2 model over Africa is similar during quiet geomagnetic conditions under both low and high solar activity periods. However, the average performance declines during disturbed geomagnetic conditions and for night-time values, while the best average performance is noticed in the daytime hmF2 predictions. The SHU-2015 model option in IRI-2016 manifests the least prediction error, best model efficiency, and correlation with the COSMIC hmF2 values, justifying the use of a large number of COSMIC profiles in the development of the SHU-2015 model. Finally, the study suggests the suitability of the SHU-2015 IRI hmF2 option over the African region when and where there are no or limited COSMIC profiles. Additionally, the research work suggests further improvements in the IRI hmF2 predictions, especially for night-time values over the African region.