NeQuick模型算法研究及性能比较

NeQuick Model Algorithm Research and Performance Assessment

  • 摘要: 研究了NeQuick2算法改进及其实现方法,从不同角度分析了NeQuick2模型在全球区域和中国区域内的性能优势。一个太阳活动周期内,中国区域NeQuick2模型计算的电子总含量(total electron content,TEC)比NeQuick1模型精度有显著提升,改正精度与太阳活动水平具有较强的相关性,低年比高年的改善效果更为显著。以全球电离层数据(global ionosphere maps,GIM)为参考标准,中国中高纬区域太阳活动低年NeQuick2模型TEC的系统年平均偏差减少了76%,年平均均方根(root mean square,RMS)值减少了约72%。太阳活动高年NeQuick2模型TEC的系统年平均偏差减少了38%,平均RMS减少了13%左右,且中高纬区域改正精度优于低纬区域11%~13%。全球区域太阳活动峰值期间NeQuick2模型TEC比NeQuick1模型日平均偏差改善了25%,日平均RMS改善了30%左右。分别用NeQuick1和NeQuick2模型得出F2层顶部区域在太阳活动峰值期电子密度随高度剖面分布,顶部电子密度剖面精度改善近40%。最后分别得出了两个模型中国区域中高纬地区E和F1层区域在100 km、150 km和200 km高度的电子密度分布图,结果显示NeQuick2模型改善了电子密度分布状况,有效避免了NeQuick1在底部区域电子密度梯度不连续以及电离层异常结构的情况。

     

    Abstract: NeQuick is an empirical model which has been selected as the GALILEO single frequency receivers' ionospheric delay correction model. The current baseline versionis the NeQuick1(ITU-R) since 2001. Based on that, the NeQuick2 version improvement and implementation method has been studied, and also the performance compare has been done in China.Firstly, the TEC accuracy has been retrieved in one solar year cycle and compared in Chinese mid-high latitude area in high/low solar activityusing NeQuick1/NeQuik2 versions. Compared with GIM, it indicates the NeQuick2 average TEC bias and RMS has been improved significantly especially in high solar activity level. In China mid-high latitude area, yearly TEC bias has been reduced 76%, 38% and yearly TEC RMS has been reduced 72%, 13% in low(2008) and high(2014) solar activity year respectively.The TEC accuracy in mid-high latitude area is 11% to 13% superior than low-latitude area. Secondly, the F2 top layer electron density profile of height has been reconstructed using the two versions, compared with ISIS2 profile data, the result showed the top layer electron density accuracy improved about 40%. Finally, the electron density at height of 100 km, 150 km, 200 km of mid-high latitude area in China has been represented, it showes that the strong gradients and strange structures appeared in E and F1 layer has disappeared in NeQuick2 version.

     

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