Comparison of TEC from GPS and IRI-2016 model over different regions of Pakistan during 2015–2017

Abstract

The rapid increase in the comparative studies between the Global Positioning System (GPS) measured Total Electron Content (TEC) and model-predicted TEC on Earth helps in mitigating the biases in the ionospheric delays of radio waves. In this paper, an evaluation on the performance of the latest International Reference Ionosphere (IRI-2016) modelled TEC is conducted with GPS TEC measurements in different regions of Pakistan during the descending phase of solar cycle 24 (2015–2017). We have analyzed the diurnal, monthly and seasonal variabilities in the measured TEC and compared with IRI-2016 modelled TEC. The diurnal variability of measured TEC is found to be maximum during 06:00–12:00 UT (11:00–17:00 LT) and minimum during 21:00–24:00 UT (02:00–05:00 LT). Moreover, maximal and minimal monthly measured TEC for each station and model are also observed in April and December, respectively. In the summer solstice months at Islamabad station during 2015–2017, the measured TEC are larger than the corresponding modelled TEC by about 19%, 22% and 24%, respectively for each year. On the other hand, the difference between the measured and modelled TEC in summer solstice at Multan station during 2015 is 25% of the normal distribution and at Quetta station during 2016 the difference is about 29% in the summer solstice. The results show that the TEC measurements from GPS coincide with TEC from IRI-2016 during the selected days by a correlation of more than 0.86, while a very high correlation coefficient (0.91–0.99) is shown during each month and season over all the stations for the years 2015–2017. IRI-2016 is a good climate model that can provide accurate estimates of ionospheric delays of radio signals propagated over Pakistan.