Performance of GPS-TEC assisted NTCM-model to describe the East-African equatorial Ionosphere

NTCM is a simple and relatively faster global climatological model that is developed, using ionospheric VTEC measurements from unevenly globally distributed GNSS receivers, to mitigate ionospheric effects on GNSS applications. As it is climatological, its ionospheric weather characteristic specification capability is limited. Also, its nowcasting and forecasting performance of the East-African equatorial ionosphere has not yet been tested. Therefore, this paper demonstrates techniques to change NTCM to ionospheric weather model to nowcast and forecast VTEC for East-Africa. NTCM has been changed to ionospheric weather model through adapting it to quiet days VTEC from nineteen GNSS receivers in East-Africa in 2013 and 2014. Adaptation has been done by calculating its driver, effective ionization level, when NTCM modeled VTEC fits the best with observed VTEC. Then, performances of the model in nowcasting and forecasting VTEC, before and after adaption, have been investigated compared to observed VTEC. It is found that NTCM, after adaptation, represents observed features of diurnal variations of VTEC and equatorial ionization anomaly (EIA) much better than before adaptation. After adaptation, the mean and standard deviation of daily mismodelings are found comparable with the mean and standard deviation of yearly mismodelings. It is demonstrated also that NTCM after adaptation to a reference station performs better than before adaptation at the stations nearby the reference station; however, its performance decreases at the locations far away from the reference station. In addition, after adaptation, one hour ahead prediction of NTCM is found to be the best compared to its longer hours prediction.