Study Of The Short-term Forecasting Of The Ionospheric TEC In China And Its Surrounding Area

The ionospheric total electron content (TEC) is one of the most important ionospheric parameters. It's variety with not only local time but also space has importance on radio system, especially on communications between the earth and the satellite. Up to now, there is no suitable method for short-term forecasting of the ionospheric TEC in China and its surrounding area. Based on the measurement data from 28 selected GPS stations, some suitable analysis methods are adopted in China and its surrounding area. In this paper, the method is studied for the short-term forecasting of ionospheric TEC. The main results are listed as follows:1. Data preparing and interpolation methods for the short-term forecasting of the ionospheric TEC. Different data handing methods have been adopted for different density of the stations to convert the original TEC data, the slant TEC, into the vertical TEC as a time series of 15 minute interval. As GPS receivers have trouble, the vertical TEC will be missing. The autocorrelation method has been adopted to interpolate the missing values using the nearest 4 days data. The errors of interpolation are ranging between 0.4 and 1.04 TECu depending on the length of the missing points.2. The characteristics of the short-term variations of the ionospheric TEC in Shanghai. These are the grand monthly median and the intensity of the monthly variability of the ionospheric TEC, the diurnal component, semi-diurnal component and random component in the auto-correlation coefficient of the ionospheric TEC in 2004. The grand monthly median reaches the biggest in April and the smallest in December. The intensity of the monthly variability has two peaks that having reached the maximum in August and in November. The diurnal component is between 0.7 and 0.9 TECu times of the intensity of the monthly variabilily and prevallent. The semi-diurnal component and random component are between 0 and 0.2 times of the intensity. The seasonal variation of the three components is smooth. The correlation time is between 5 and 30 hours.3. Putting forward a suitable method of short-term forecasting of the ionosphric TEC in China and its surrounding area. This method consists of two parts: the single station ionospheric forecasting and the regional ionospheric reconstruction. The auto-correlation method has been adopted in the single station forecasting. The prediction error of the single station forecasting for 15 minute up to 24 hours ahead varies from 0.75 to 3.75 TECu. The improved Kriging method has been adopted in the regional ionospheric reconstruction. The error of the reconstruction is between 0.36 and 4.33 TECu depending on the location. The single station forecasting and the reconstruction is putted together to realize the short-time forecasting of TEC in China and its surrounding area. Based on the systematic measurement data from 28 selected GPS stations in 2004, the computing simulations of the short-term forecasting have been done for different places, days and hours to give the estimates of the prediction's errors. At the end, the causes of the prediction errors have studied and the possible ways have given to improve the forecasting.