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

Abstract

[1] The ability of the Utah State University (USU) Global Assimilation of Ionospheric Measurements (GAIM) model to specify the day-to-day variability of the ionosphere is assessed by comparison of specified hourly values of foF2 with observations that were not assimilated by the model. If the specifications are to be an improvement over a climatological model with zero average error, the interdecile width of errors of the specifications at each hour must be less than the interdecile width of the observations. It has been found that the median specified values of foF2 for undisturbed days are quite accurate, and that the interdecile width of errors of the specifications is less than that of the observations most of the time for midlatitude sites, provided there is a GPS TEC site sufficiently close to the ionosonde site. The errors in GAIM values of foF2 for Australian locations tend to be larger for larger distances from a GPS site, and for low latitudes. GAIM also tracks the values of foF2 on disturbed days, but tends to be conservative, not reproducing the full extent of the departures of the disturbed values from the background values.

Real‐time specification of HF propagation support based on a global assimilative model of the ionosphere

“…Figure 4 shows that this situation holds for the HFNowcast FMUFs, although the improvement provided by GAIM is not particularly large. This is in contrast to the observation by Decker and McNamara [2007] that USU‐GAIM successfully reproduced a portion of the Australian ionospheric weather in foF2 for March/April 2004.…”

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

“…For near vertical incidence circuits, the ordinary ray instantaneous MUF is equal to f o F 2 , and GAIM has been shown to track even the day‐to‐day variability of f o F 2 (the “weather” in f o F 2 ) at Australian locations quite well [ Decker and McNamara , 2007]. For one‐hop circuits lengths between zero and 3000 km, the profile shape between the E and F layer peaks (the F 1 region) will be important.…”

“…Nevertheless, there were several days for which the observed values of f o F 2 were significantly different from the monthly median. A detailed comparison of the GAIM and observed values has shown that GAIM tends to track the disturbed days, but generally tends to be conservative, not matching the extent of the departures of the disturbed days from the median values [ Decker and McNamara , 2007].…”

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.…”