A single-station empirical TEC model based on long-time recorded GPS data for estimating ionospheric delay

Abstract

Globally distributed GPS (global positioning system) stations have been continuously running for nearly 20 years, thereby accumulating numerous observations. These long-time recorded GPS data can be used to calculate continuous total electron content (TEC) values at single stations and provide an effective modeling dataset to establish single-station empirical TEC models. In this paper, a new empirical TEC model called SSM-T1 for single stations is proposed on the basis of GPS data calculated by IONOLAB-TEC application from 2004 to 2015. The SSM-T1 model consists of three parts: diurnal, seasonal, and solar dependency variations, with 18 coefficients fitted by the nonlinear least-squares method. The SSM-T1 model is tested at four stations: Paris (opmt), France; Bangalore (iisc), India; Ceduna (cedu), Australia; and O’Higgins (ohi3) over the Antarctic Peninsula. The RMS values of the model residuals at these four stations are 3.22, 4.46, 3.28, and 3.83 TECU. Assessment results show that the SSM-T1 model is in good agreement with the observed GPS-TEC data and exhibits good prediction ability at the Paris, Bangalore, and Ceduna stations. However, at the O’Higgins station, the SSM-T1 model seriously deviates from the observed GPS-TEC data and cannot effectively describe the variation of mid-latitude summer night anomaly.

A New Global Total Electron Content Empirical Model

“…Furthermore, global TEC data were selected under geomagnetic conditions. Following the example of previous studies [33,[38][39][40], GIMs TEC data for which the Ap index exceed 30.0 were not considered for modelling.…”

“…Two different TEC empirical models, SSM-T1 and SSM-T2, are employed for grid points in different regions. SSM-T1, which was proposed in our previous study, exhibits good fit and forecasting precision on testing stations at the middle and low latitudes, but is unsuitable for stations in the MSNA area [33]. SSM-T1 can be used for single grid point modelling in areas other than MSNA.…”

“…Thus, the variation characteristics mainly include the diurnal, seasonal and solar variations of TEC. Then, the single grid point TEC empirical model can be expressed in the form of multiplying three components [33]: F represents the variation that is dependent on solar activity. SSM-T1 is a function of day of year (DOY), local time (LT) and solar activity parameters.…”

“…Thus, the variation characteristics mainly include the diurnal, seasonal and solar variations of TEC. Then, the single grid point TEC empirical model can be expressed in the form of multiplying three components [33]:…”

“…Through the fitting test and model comparison, the SSM-T1 model is found unsuitable for stations in the MSNA area [33]. For grid points in the MSNA area, a new TEC empirical model SSM-T2 is proposed here.…”