Validation of the Utah State University Global Assimilation of Ionospheric Measurements (GAIM) model predictions of the maximum usable frequency for a 3000 km circuit

Abstract

The accuracy of the Utah State University Global Assimilation of Ionospheric Measurements (GAIM) monthly median values of the maximum usable frequency for an HF communications circuit has been determined for 3000 km circuits centered on Australian ionosonde locations for March and April 2004. The accuracy is discussed in terms of foF2, M(3000)F2, and the product MUF(3000)F2 = foF2 * M(3000)F2. Ground truth is provided by hourly values of foF2 and M(3000)F2 that have been hand‐scaled from ionograms. In general, the accuracy of the GAIM predictions of foF2 exceeds that for M(3000)F2. Given that M(3000)F2 is a function of the height and shape of the F2 subpeak, it follows that these parameters of the GAIM F2 peak need to be improved. The GAIM errors in foF2 are quite large at Learmonth during the day, even though Learmonth is a digital ionospheric sounding systems (DISS) station that provides real‐time data to GAIM. We interpret these errors in terms of limitations of the current GAIM model. Comparisons of the GAIM errors in the monthly median MUF(3000)F2 with those given by the propagation prediction program Advanced Stand Alone Prediction System (ASAPS) show that the GAIM errors are generally somewhat greater than the ASAPS errors, but we consider GAIM's performance to be creditable given that most of the data available for assimilation is GPS total electron content observations. Overall, the daytime GAIM errors are 3 MHz or 10%, while the nighttime errors are 3 MHz or 16%. On average, the GAIM errors are about 3/2 the ASAPS errors during the day and twice the ASAPS errors at night.

Tomography of the ionospheric electron density with geostatistical inversion

“…For both ionosonde locations, the mean and the RMS error of NmF2 are decreased whereas no reduction is obtained for the hmF2 errors. Similar results are obtained by McNamara et al (2007). McNamara et al (2007) compare foF2 and the maximum usable frequency factor M(3000)F2 estimated by the Utah State University Global Assimilation of Ionospheric Measurements (GAIM) model with Australian ionosonde station data.…”

“…Similar results are obtained by McNamara et al (2007). McNamara et al (2007) compare foF2 and the maximum usable frequency factor M(3000)F2 estimated by the Utah State University Global Assimilation of Ionospheric Measurements (GAIM) model with Australian ionosonde station data. They observed that GAIM reproduces foF2 better than M(3000)F2, which is related to hmF2.…”

The IONORT-ISP-WC system: Inclusion of an electron collision frequency model for the D-layer

“…A comprehensive specification of the ionosphere in terms of electron density, neutral particles-electrons collision frequency, and geomagnetic field is required in order to carry out an accurate ray-tracing. Therefore, when dealing with near real-time applications of ray-tracing, it is of crucial importance to have a realistic ionospheric modelling through 3-D models of ionospheric electron density, which after assimilating measured data calculate an updated 3-D image of the ionosphere (Angling and Khattatov, 2006;Thompson et al, 2006;Fridman et al, 2006Fridman et al, , 2009Decker and McNamara, 2007;McNamara et al, 2007McNamara et al, , 2008McNamara et al, , 2010McNamara et al, , 2011McNamara et al, , 2013Angling and Jackson-Booth, 2011;Shim et al, 2011). More recently, at the INGV, the IRI-SIRMUP-PROFILES (ISP) model, capable of providing a 3-D electron density profile representation of the ionosphere in quasi real time, was developed.…”

Validation of ionospheric weather predicted by Global Assimilation of Ionospheric Measurements (GAIM) models

“…Plasma frequency profiles from this network of Digisondes (operated by the United States Air Force Weather Agency) are the source of EDP data assimilated by the GMKF. We have shown elsewhere [ McNamara et al , 2007] that the GMKF predicted values of foF2 for Learmonth are not accurate during the day, presumably because the GMKF model gives greater weight to the TEC observations from a nearby GPS TEC site than it does to the DISS observations.…”