An empirical model of ionospheric foE over Wuhan

Daytime half-hourly values of the critical frequency of the ionospheric E-layer, f oE, obtained at Wuhan Ionospheric Observatory (geographic 114.4 degrees E, 30.6 degrees N; 45.2 degrees dip), China, during the whole interval of 1957-1991 and 1999-2004 have been used to develop an empirical model. The model, including variations with local time, day number and solar cycle, is in agreement with the observations. A comparison between our model and IRI and Titheridge's model has also been made. Statistically, our model gives a better performance than IRI and Titheridge's model because data set is obtained with our own station. Both the IRI and Titheridge's model overestimate f oE especially in May to September months. Combing with past investigations, we suggest that overestimation of ionospheric parameters by IRI may be a common feature in East Asia. This result is very helpful for both the correction of IRI in East Asia and the development of Chinese Reference Ionosphere (CRI) model.