A statistical comparison of IRI TEC prediction with GPS TEC measurement over Varanasi, India

• To validate the latest IRI model, GPS TEC values for year 2012–2013 compared with those derived from the IRI-2012.
• The IRI TEC values generally compared well with the GPS TEC values, having correlation coefficients about 0.9.
• The root-mean square deviations (RMSD) vary around 25–70% for diurnal comparisons.
• The IRI-2001 model significantly overestimates during the winter season of 2012–2013.
• The winter anomaly is verified by comparing the foF2 data from COSMIC with IRI model.

The widely used International Reference Ionosphere (IRI) model in simulation/modeling of ionospheric studies specially at low latitudes require performance evaluation. To achieve this objective, we have compared total electron content (TEC) derived from the recent version of IRI model (IRI-2012) over low latitude Indian station Varanasi (Geographic: 25°16′N, 82°59′E; Geomagnetic: 14°55′N, 154°E) with TEC measured from the GPS receiver installed at Varanasi. The results are in good agreement with correlation coefficient ~0.9, and root-mean square deviations generally around 25–70% for diurnal comparisons. The seasonal variability of TEC derived by using the different topside options of the IRI-2012 model (IRI-2001, NeQuick and IRI01-corr) are studied and validated for the three seasons. The IRI-2012 model with all the three topside options significantly overestimates TEC for the station during the winter season of 2012–2013, which has been attributed to discrepancy in foF2 parameter as predicted by the model during the winter season of 2012–2013. This has been confirmed by comparing the foF2 data from COSMIC with IRI model.