Abstract
Abstract. According to the empirical orthogonal function (EOF), the non-stationary time series data are decomposed into time function and space function, so this mathematical method can simplify the non-stationary time series and eliminate redundant information, thus it performs well in non-stationary time series analysis. The ionospheric Vertical Total Electron Content (VTEC) is a non-stationary time series, which has non-stationary and seasonal variation and the activity of VTEC is more active in low latitudes. Guangxi is located in the middle and low latitudes of the Northern Hemisphere with abundant sunshine in summer and autumn. The energy released by solar radiation makes the ionospheric activity in this region more complex than that in the high latitudes. However, no expert or scholar has used EOF analysis method to conduct a comprehensive study of the low latitudes. The International GNSS Service (IGS) provided by high precision Global Ionospheric Maps (GIM) center in Guangxi are used in the modeling data, the GIM data of the first 10 days of different seasons are decomposed by EOF, and then the time function is predicted by ARIMA model. VTEC values for the next five days are obtained through reconstruction, and relative accuracy and standard deviation are used as accuracy evaluation criteria. The results of EOF-ARIMA model are compared with those of ARIMA model, and the prediction accuracy of EOF-ARIMA model at the equatorial anomaly is analyzed in order to explore the reliability of the model in the more complex region of ionospheric activity. The results show that the average relative precision of EOF-ARIMA model is 84.0, the average standard deviation is 7.45TECu, the average relative precision of ARIMA model is 81.5, the average standard deviation is 8.29TECu, and the precision of EOF-ARIMA model is higher than that of ARIMA model.; There is no significant seasonal difference in the prediction accuracy of EOF-ARIMA model, and the prediction accuracy of ARIMA model in autumn is lower than that of other seasons, which indicates that the prediction results of EOF-ARIMA model are more reliable; The prediction accuracy of the EOF-ARIMA model at the equatorial anomaly is not affected, and it is consistent with the accuracy of the high latitude area in Guangxi. It is shown that the EOF-ARIMA model has high accuracy and stability in the short-term ionospheric prediction in Guangxi at low latitudes of China, and provides a new and reliable method for ionospheric prediction at low latitudes.
Highlights
Total ionospheric electron content is an important parameter to characterize ionospheric delay
Improving the prediction accuracy of Vertical Total Electron Content (VTEC) can improve the positioning accuracy of Global Navigation Satellite System (GNSS).In addition, it is of great significance in the fields of pre-earthquake ionospheric disturbance, earth magnetic field research, and the influence of solar activity on the ionosphere [1,2,3].The commonly used VTEC prediction models mainly include grey model [4], neural network model [5], Holt-Winters model [6,7], ARMA model [8] and ARIMA model [9].Among them, the neural network model can be infinitely close to the complex non-linear relationship, and it can be well used in the prediction of VTEC
As can be seen from table 1, in the same season, the relative accuracy and standard deviation of empirical orthogonal function (EOF)-ARIMA model remain in the same prediction accuracy and are more stable than ARIMA model, which further indicates that EOF-ARIMA model has better stability in the short-term VTEC prediction in Guangxi region
Summary
Total ionospheric electron content is an important parameter to characterize ionospheric delay. Few literatures have introduced EOF function into ARIMA model for short-term prediction of ionospheric VTEC in Guangxi region. The ionosphere in this area has equatorial anomalies [14], and is a frequent area of typhoons, volcanoes and earthquakes [15,16]. High-precision VTEC prediction values can provide important data sources for the seismic prediction analysis [17] of Guangxi region and the analysis of the impact of typhoons on the ionosphere [18].it is of great significance to explore the use of EOF- ARIMA model to predict ionospheric VTEC values in Guangxi region (20°~27.5°N, 100°~115°E)
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