综合多种方法分析中国区域TEC时空变化特征

ANALYSIS OF TEMPORAL-SPATIAL VARIATIONS OF TEC IN CHINA WITH SEVERAL METHODS

基于时序分析、频谱分析和小波分解方法,利用1999～2013年IGS全球电离层格网数据,对中国区域TEC年际变化、季节变化、日变化及空间分布特性进行研究。结果显示,TEC随空间分布白天差异大而夜间较小;总体上在低纬地区高于中纬地区,在冬季存在异常;一天中,其峰值一般出现在LT12：00～16：00,谷值在LT04：00～06：00,其中峰值时刻随纬度的增大而向前推移;平静期TEC在春季出现一年中的峰值,而活跃期则在秋季;TEC存在明显的183 d的半年周期。另外,中国区域除2001年外不存在＂冬季异常＂现象。

The interannual variation, seasonal variation, diurnal variation and spatial distribution characteristics of TEC in China are investigated with time series analysis, spectrum analysis and wavelet decomposition using the global ionospheric grid data provided by IGS from 1999 to 2013. The main features are as the followings ：TEC varies greatly in the daytime while slightly in the night with the spatial distribution;overall, the TEC value in the low latitude area is higher than that in the mid latitude. In the winter, TEC value in the low latitude is lower than that in the mid-latitude. Within a day,peak value appears during LT 12：00-16：00 and valley appears during LT4：00-6：00. In the periods, the peak time moves forward with the increase of latitude. This rule may provide certain reference to modify K8 model which set peak time as fixed. The spring is quiet period, in which TEC reaches its maximum value of a year, and the autumn is active period. TEC has obvious semiannual period of about 183 days. In addition, the a- nalysis of long time sequence shows that winter anomaly does not exist in China, except in 2001.