| Summary: | The ionograms, which were recorded by the ionosonde located at Pu’er station (PUR, 22.7° N, 101.05° E, Dip Latitude 12.9° N) in the Southwest of China in the year of 2016, were used to study the ionospheric behavior of the ordinary critical frequency of the F2 layer (<i>fo</i>F2) in the region of the northern equatorial ionization anomaly. To verify the performance of the International Reference Ionosphere (IRI) over the Southwest of China, a comparative study of the observed <i>fo</i>F2 and the latest version of the International Reference Ionosphere (IRI-2016) was carried out. We found that the <i>fo</i>F2 in equinox months is greater than summer and winter. Moreover, a higher frequency of the observed bite-out of <i>fo</i>F2 in January and April than other months and the IRI-2016 cannot represent the bite-out of <i>fo</i>F2 in diurnal variations. Compared to the observations at Pu’er Station, the IRI-2016 underestimated <i>fo</i>F2 for most time of the year. The IRI with the International Radio Consultative Committee (CCIR) option overestimated <i>fo</i>F2 is higher than that with the International Union of Radio Science (URSI) option. Furthermore, the normalized root mean square error of <i>fo</i>F2 from the IRI-2016 with the CCIR option is less than that with the URSI.
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